guanfacine (Rx)

Brand and Other Names:Intuniv, Tenex
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Dosing & Uses

AdultPediatric

Dosage Forms & Strengths

tablet (Tenex)

  • 1mg
  • 2mg

Hypertension

Tenex: 1 mg PO qHS; may increase to 2 mg after 3-4 weeks

Usual range 0.5-2 mg/day

Do not exceed 3 mg qDay due to increased risk of adverse effects

Heroin Withdrawal (Off-label)

0.03-1.75 mg/day PO for 5-15 days

Migraine Prophylaxis (Off-label)

Initial: 1 mg/day; do not exceed 3 mg/day

Fragile X Syndrome (Orphan)

Orphan sponsor

  • Watson Laboratories, Inc; 311 Bonnie Circle, PO Box 1900; Corona, CA 91718-1900

Dosage Modifications

Strong or moderate CYP3A4 inhibitors

  • Strong or moderate CYP3A4 inhibitors significantly increase guanfacine plasma concentrations
  • FDA-labeling for extended-release (ER) guanfacine recommends that, if coadministered, the guanfacine dosage should be decreased to half of the reommended dose; specific recommendations for immediate-release (IR) guanfacine are not available
  • Starting therapy while currently taking CYP3A4 inhibitor: Decrease dose to half the recommended level
  • Continuing therapy while adding CYP3A4 inhibitor: Decrease dose to half the recommended level
  • Continuing therapy while stopping CYP3A4 inhibitor: Increase dose to recommended level

Strong or moderate CYP3A4 inducers

  • CYP3A4 inducers significantly reduce guanfacine plasma concentrations and elimination half-life
  • If coadministered, more frequent dosing of the IR product may be required to achieve or maintain the desired hypotensive response
  • For patients with ADHD, FDA-approved labeling for ER guanfacine recommends that, if coadministered, doubling the recommended dose of guanfacine should be considered
  • Starting therapy while currently taking CYP3A4 inducer: Increase dose up to double the recommended level
  • Continuing therapy while adding CYP3A4 inducer: Increase dose up to double the recommended level over 1-2 weeks
  • Continuing therapy while stopping CYP3A4 inducer: Increase dose to recommended level

Discontinuation of therapy

  • To minimize risk of rebound hypertension upon discontinuation, taper total daily dose in decrements of no more than 1 mg every 3 to 7 days; blood pressure and heart rate should be monitored when reducing dose or discontinuing therapy; follow patients closely for rebound hypertension if abrupt discontinuation occurs (especially with concomitant stimulant use)

Dosage Forms & Strengths

tablet (Tenex)

  • 1mg
  • 2mg

tablet, extended-release (Intuniv)

  • 1mg
  • 2mg
  • 3mg
  • 4mg

Hypertension

<12 years

  • Safety and efficacy not established

≥12 years

  • Tenex: 1 mg PO qHS; may increase to 2-3 mg after 3-4 weeks
  • Usual range: 0.5-2 mg/day

Attention Deficit Hyperactivity Disorder

Intuniv only

Monotherapy for ADHD or adjunct to stimulants

<6 years: Safety and efficacy not established

6-18 years

  • Intuniv: 1 mg/day PO initially; may adjust dose using increasing increments (not exceeding 1 mg/wk)
  • To balance the exposure-related potential benefits and risks, recommended target dose range depending on clinical response and tolerability is 0.05-0.12 mg/kg/day PO initially  
  • Aged 6-12 years: Doses >4 mg/day not evaluated
  • Aged 13-17 years: Doses >7 mg/day not evaluated
  • Adjunctive trials with psychostimulants: Doses >4 mg/day not evaluated

Target dose range by weight

  • 25-33.9 kg: 2-3 mg/day
  • 34-41.4 kg: 2-4 mg/day
  • 41.5-49.4 kg: 3-5 mg/day
  • 49.5-58.4 kg: 3-6 mg/day
  • 58.5-91 kg: 4-7 mg/day
  • >91 kg: 5-7 mg/day

Dosage Modifications

Extended-release tablets

  • Renal impairment: Dose reduction may be necessary in patients with significant impairment of renal function
  • Hepatic impairment: Dose reduction may be necessary in patients with significant impairment of hepatic function

Strong or moderate CYP3A4 inhibitors

  • Strong or moderate CYP3A4 inhibitors (eg, ketoconazole) significantly increase guanfacine plasma concentrations
  • Starting therapy while currently taking CYP3A4 inhibitor: Decrease dose to half the recommended level
  • Continuing therapy while adding CYP3A4 inhibitor: Decrease dose to half the recommended level
  • Continuing therapy while stopping CYP3A4 inhibitor: Increase dose to recommended level

Strong or moderate CYP3A4 inducers

  • CYP3A4 inducers (eg, carbamazepine) significantly reduce guanfacine plasma concentrations and elimination half-life
  • If coadministered, more frequent dosing of the IR product may be required to achieve or maintain the desired hypotensive response
  • Extended-release tablets
    • Starting therapy while currently taking CYP3A4 inducer: Increase dose up to double the recommended level
    • Continuing therapy while adding CYP3A4 inducer: Increase dose up to double the recommended level over 1-2 weeks
    • Continuing therapy while stopping CYP3A4 inducer: Decrease dose to recommended level over 1-2 weeks

Dosing Considerations

Immediate-release and extended-release formulations are not interchangeable due to differences in bioavailability

If switching from immediate-release guanfacine, discontinue treatment; titrate with extended-release tablets following recommended schedule

Discontinuation of extended-release guanfacine

  • Following discontinuation of extended-release tablets, patients may experience increases in blood pressure and heart rate
  • Monitor blood pressure and pulse when reducing dose or discontinuing treatment
  • Taper daily dose in decrements of ≤1 mg q3-7d to minimize the risk of rebound hypertension

Tourette Syndrome (Orphan)

Orphan designation for combination of guanfacine and amphetamine to treatment Tourette syndrome

Sponsor

  • Genco Sciences, LLC; 1011 Greenwood Avenue; Willmette, Illinois 60091
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Interactions

Interaction Checker

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              Serious - Use Alternative (27)

              • abametapir

                abametapir will increase the level or effect of guanfacine by affecting hepatic/intestinal enzyme CYP3A4 metabolism. Avoid or Use Alternate Drug. For 2 weeks after abametapir application, avoid taking drugs that are CYP3A4 substrates. If not feasible, avoid use of abametapir.

              • amitriptyline

                amitriptyline decreases effects of guanfacine by Other (see comment). Avoid or Use Alternate Drug. Comment: Inhibition of uptake by adrenergic neurons.

              • amoxapine

                amoxapine decreases effects of guanfacine by Other (see comment). Avoid or Use Alternate Drug. Comment: Inhibition of uptake by adrenergic neurons.

              • apalutamide

                apalutamide will decrease the level or effect of guanfacine by affecting hepatic/intestinal enzyme CYP3A4 metabolism. Avoid or Use Alternate Drug. Coadministration of apalutamide, a strong CYP3A4 inducer, with drugs that are CYP3A4 substrates can result in lower exposure to these medications. Avoid or substitute another drug for these medications when possible. Evaluate for loss of therapeutic effect if medication must be coadministered. Adjust dose according to prescribing information if needed.

              • chloramphenicol

                chloramphenicol will increase the level or effect of guanfacine by affecting hepatic/intestinal enzyme CYP3A4 metabolism. Avoid or Use Alternate Drug.

              • clomipramine

                clomipramine decreases effects of guanfacine by Other (see comment). Avoid or Use Alternate Drug. Comment: Inhibition of uptake by adrenergic neurons.

              • cobicistat

                cobicistat will increase the level or effect of guanfacine by affecting hepatic/intestinal enzyme CYP3A4 metabolism. Avoid or Use Alternate Drug.

              • desipramine

                desipramine decreases effects of guanfacine by Other (see comment). Avoid or Use Alternate Drug. Comment: Inhibition of uptake by adrenergic neurons.

              • doxepin

                doxepin decreases effects of guanfacine by Other (see comment). Avoid or Use Alternate Drug. Comment: Inhibition of uptake by adrenergic neurons.

              • fexinidazole

                fexinidazole will increase the level or effect of guanfacine by affecting hepatic/intestinal enzyme CYP3A4 metabolism. Avoid or Use Alternate Drug. Fexinidazole inhibits CYP3A4. Coadministration may increase risk for adverse effects of CYP3A4 substrates.

              • imipramine

                imipramine decreases effects of guanfacine by Other (see comment). Avoid or Use Alternate Drug. Comment: Inhibition of uptake by adrenergic neurons.

              • iobenguane I 131

                guanfacine will decrease the level or effect of iobenguane I 131 by Other (see comment). Avoid or Use Alternate Drug. Based on the mechanism of action of iobenguane, drugs that reduce catecholamine uptake or that deplete catecholamine stores may interfere with iobenguane uptake into cells, and thus, reduce iobenguane efficacy. Discontinue interfering drugs for at least 5 half-lives before administration of either the dosimetry or an iobenguane dose. Do not administer these drugs until at least 7 days after each iobenguane dose.

              • ivosidenib

                ivosidenib will decrease the level or effect of guanfacine by affecting hepatic/intestinal enzyme CYP3A4 metabolism. Avoid or Use Alternate Drug. Avoid coadministration of sensitive CYP3A4 substrates with ivosidenib or replace with alternate therapies. If coadministration is unavoidable, monitor patients for loss of therapeutic effect of these drugs.

              • lofepramine

                lofepramine decreases effects of guanfacine by Other (see comment). Avoid or Use Alternate Drug. Comment: Inhibition of uptake by adrenergic neurons.

              • lofexidine

                lofexidine, guanfacine. Either increases effects of the other by pharmacodynamic synergism. Avoid or Use Alternate Drug. Avoid coadministration with other drugs that decrease pulse or blood pressure to mitigate risk of excessive bradycardia and hypotension.

              • lorlatinib

                lorlatinib will decrease the level or effect of guanfacine by affecting hepatic/intestinal enzyme CYP3A4 metabolism. Avoid or Use Alternate Drug.

              • maprotiline

                maprotiline decreases effects of guanfacine by Other (see comment). Avoid or Use Alternate Drug. Comment: Inhibition of uptake by adrenergic neurons.

              • metoclopramide intranasal

                guanfacine, metoclopramide intranasal. Either increases effects of the other by Other (see comment). Avoid or Use Alternate Drug. Comment: Avoid use of metoclopramide intranasal or interacting drug, depending on importance of drug to patient.

              • mifepristone

                mifepristone will increase the level or effect of guanfacine by affecting hepatic/intestinal enzyme CYP3A4 metabolism. Avoid or Use Alternate Drug.

              • mirtazapine

                mirtazapine decreases effects of guanfacine by pharmacodynamic antagonism. Avoid or Use Alternate Drug. Risk of hypertensive urgency.

              • nortriptyline

                nortriptyline decreases effects of guanfacine by Other (see comment). Avoid or Use Alternate Drug. Comment: Inhibition of uptake by adrenergic neurons.

              • ponesimod

                ponesimod, guanfacine. Either increases effects of the other by pharmacodynamic synergism. Avoid or Use Alternate Drug. Consult cardiologist if considering treatment. Coadministration of ponesimod with drugs that decrease HR may have additive effects on decreasing HR and should generally not be initiated in these patients.

              • protriptyline

                protriptyline decreases effects of guanfacine by Other (see comment). Avoid or Use Alternate Drug. Comment: Inhibition of uptake by adrenergic neurons.

              • trazodone

                trazodone decreases effects of guanfacine by Other (see comment). Avoid or Use Alternate Drug. Comment: Inhibition of uptake by adrenergic neurons.

              • trimipramine

                trimipramine decreases effects of guanfacine by Other (see comment). Avoid or Use Alternate Drug. Comment: Inhibition of uptake by adrenergic neurons.

              • tucatinib

                tucatinib will increase the level or effect of guanfacine by affecting hepatic/intestinal enzyme CYP3A4 metabolism. Avoid or Use Alternate Drug. Avoid concomitant use of tucatinib with CYP3A substrates, where minimal concentration changes may lead to serious or life-threatening toxicities. If unavoidable, reduce CYP3A substrate dose according to product labeling.

              • voxelotor

                voxelotor will increase the level or effect of guanfacine by affecting hepatic/intestinal enzyme CYP3A4 metabolism. Avoid or Use Alternate Drug. Voxelotor increases systemic exposure of sensitive CYP3A4 substrates. Avoid coadministration with sensitive CYP3A4 substrates with a narrow therapeutic index. Consider dose reduction of the sensitive CYP3A4 substrate(s) if unable to avoid.

              Monitor Closely (135)

              • aldesleukin

                aldesleukin increases effects of guanfacine by pharmacodynamic synergism. Use Caution/Monitor. Risk of hypotension.

              • amifostine

                amifostine, guanfacine. Either increases effects of the other by pharmacodynamic synergism. Modify Therapy/Monitor Closely. Coadministration with blood pressure lowering agents may increase the risk and severity of hypotension associated with amifostine. When amifostine is used at chemotherapeutic doses, withhold blood pressure lowering medications for 24 hr prior to amifostine; if blood pressure lowering medication cannot be withheld, do not administer amifostine.

              • amiodarone

                amiodarone will increase the level or effect of guanfacine by affecting hepatic/intestinal enzyme CYP3A4 metabolism. Modify Therapy/Monitor Closely. Strong or moderate CYP3A4 inhibitors significantly increase guanfacine plasma concentrations. FDA-approved labeling for extended-release (ER) guanfacine recommends that, if coadministered, the guanfacine dosage should be decreased to half of the recommended dose. Specific recommendations for immediate-release (IR) guanfacine are not available.

              • amobarbital

                amobarbital will decrease the level or effect of guanfacine by affecting hepatic/intestinal enzyme CYP3A4 metabolism. Modify Therapy/Monitor Closely. Strong or moderate CYP3A4 inducers significantly reduce guanfacine plasma concentrations and elimination half-life. If coadministered, more frequent dosing of the IR product may be required to achieve or maintain the desired hypotensive response. For patients with ADHD, FDA-approved labeling for ER guanfacine recommends that, if coadministered, doubling the recommended dose of guanfacine should be considered.

              • aprepitant

                aprepitant will increase the level or effect of guanfacine by affecting hepatic/intestinal enzyme CYP3A4 metabolism. Modify Therapy/Monitor Closely. Strong or moderate CYP3A4 inhibitors significantly increase guanfacine plasma concentrations. FDA-approved labeling for extended-release (ER) guanfacine recommends that, if coadministered, the guanfacine dosage should be decreased to half of the recommended dose. Specific recommendations for immediate-release (IR) guanfacine are not available.

              • aripiprazole

                guanfacine, aripiprazole. Mechanism: pharmacodynamic synergism. Use Caution/Monitor. Additive hypotensive effects; potential delirium.

              • armodafinil

                armodafinil will decrease the level or effect of guanfacine by affecting hepatic/intestinal enzyme CYP3A4 metabolism. Modify Therapy/Monitor Closely. Strong or moderate CYP3A4 inducers significantly reduce guanfacine plasma concentrations and elimination half-life. If coadministered, more frequent dosing of the IR product may be required to achieve or maintain the desired hypotensive response. For patients with ADHD, FDA-approved labeling for ER guanfacine recommends that, if coadministered, doubling the recommended dose of guanfacine should be considered.

              • artemether/lumefantrine

                artemether/lumefantrine will decrease the level or effect of guanfacine by affecting hepatic/intestinal enzyme CYP3A4 metabolism. Use Caution/Monitor.

              • atazanavir

                atazanavir will increase the level or effect of guanfacine by affecting hepatic/intestinal enzyme CYP3A4 metabolism. Modify Therapy/Monitor Closely. Strong or moderate CYP3A4 inhibitors significantly increase guanfacine plasma concentrations. FDA-approved labeling for extended-release (ER) guanfacine recommends that, if coadministered, the guanfacine dosage should be decreased to half of the recommended dose. Specific recommendations for immediate-release (IR) guanfacine are not available.

              • avanafil

                avanafil increases effects of guanfacine by pharmacodynamic synergism. Use Caution/Monitor. Risk of hypotension.

              • belzutifan

                belzutifan will decrease the level or effect of guanfacine by affecting hepatic/intestinal enzyme CYP3A4 metabolism. Modify Therapy/Monitor Closely. If unable to avoid coadministration of belzutifan with sensitive CYP3A4 substrates, consider increasing the sensitive CYP3A4 substrate dose in accordance with its prescribing information.

              • benperidol

                guanfacine, benperidol. Mechanism: pharmacodynamic synergism. Use Caution/Monitor. Additive hypotensive effects; potential delirium.

              • bicalutamide

                bicalutamide will increase the level or effect of guanfacine by affecting hepatic/intestinal enzyme CYP3A4 metabolism. Modify Therapy/Monitor Closely. Strong or moderate CYP3A4 inhibitors significantly increase guanfacine plasma concentrations. FDA-approved labeling for extended-release (ER) guanfacine recommends that, if coadministered, the guanfacine dosage should be decreased to half of the recommended dose. Specific recommendations for immediate-release (IR) guanfacine are not available.

              • bosentan

                bosentan will decrease the level or effect of guanfacine by affecting hepatic/intestinal enzyme CYP3A4 metabolism. Modify Therapy/Monitor Closely. Strong or moderate CYP3A4 inducers significantly reduce guanfacine plasma concentrations and elimination half-life. If coadministered, more frequent dosing of the IR product may be required to achieve or maintain the desired hypotensive response. For patients with ADHD, FDA-approved labeling for ER guanfacine recommends that, if coadministered, doubling the recommended dose of guanfacine should be considered.

              • brexanolone

                brexanolone, guanfacine. Either increases toxicity of the other by sedation. Use Caution/Monitor.

              • butabarbital

                butabarbital will decrease the level or effect of guanfacine by affecting hepatic/intestinal enzyme CYP3A4 metabolism. Modify Therapy/Monitor Closely. Strong or moderate CYP3A4 inducers significantly reduce guanfacine plasma concentrations and elimination half-life. If coadministered, more frequent dosing of the IR product may be required to achieve or maintain the desired hypotensive response. For patients with ADHD, FDA-approved labeling for ER guanfacine recommends that, if coadministered, doubling the recommended dose of guanfacine should be considered.

              • butalbital

                butalbital will decrease the level or effect of guanfacine by affecting hepatic/intestinal enzyme CYP3A4 metabolism. Modify Therapy/Monitor Closely. Strong or moderate CYP3A4 inducers significantly reduce guanfacine plasma concentrations and elimination half-life. If coadministered, more frequent dosing of the IR product may be required to achieve or maintain the desired hypotensive response. For patients with ADHD, FDA-approved labeling for ER guanfacine recommends that, if coadministered, doubling the recommended dose of guanfacine should be considered.

              • carbamazepine

                carbamazepine will decrease the level or effect of guanfacine by affecting hepatic/intestinal enzyme CYP3A4 metabolism. Modify Therapy/Monitor Closely. Strong or moderate CYP3A4 inducers significantly reduce guanfacine plasma concentrations and elimination half-life. If coadministered, more frequent dosing of the IR product may be required to achieve or maintain the desired hypotensive response. For patients with ADHD, FDA-approved labeling for ER guanfacine recommends that, if coadministered, doubling the recommended dose of guanfacine should be considered.

              • carbidopa

                carbidopa increases effects of guanfacine by pharmacodynamic synergism. Use Caution/Monitor. Therapy with carbidopa, given with or without levodopa or carbidopa-levodopa combination products, is started, dosage adjustment of the antihypertensive drug may be required.

              • cenobamate

                cenobamate will decrease the level or effect of guanfacine by affecting hepatic/intestinal enzyme CYP3A4 metabolism. Modify Therapy/Monitor Closely. Increase dose of CYP3A4 substrate, as needed, when coadministered with cenobamate.

              • ceritinib

                ceritinib will increase the level or effect of guanfacine by affecting hepatic/intestinal enzyme CYP3A4 metabolism. Modify Therapy/Monitor Closely. Strong or moderate CYP3A4 inhibitors significantly increase guanfacine plasma concentrations. FDA-approved labeling for extended-release (ER) guanfacine recommends that, if coadministered, the guanfacine dosage should be decreased to half of the recommended dose. Specific recommendations for immediate-release (IR) guanfacine are not available.

              • chlorpromazine

                guanfacine, chlorpromazine. Mechanism: pharmacodynamic synergism. Use Caution/Monitor. Additive hypotensive effects; potential delirium.

              • clarithromycin

                clarithromycin will increase the level or effect of guanfacine by affecting hepatic/intestinal enzyme CYP3A4 metabolism. Modify Therapy/Monitor Closely. Strong or moderate CYP3A4 inhibitors significantly increase guanfacine plasma concentrations. FDA-approved labeling for extended-release (ER) guanfacine recommends that, if coadministered, the guanfacine dosage should be decreased to half of the recommended dose. Specific recommendations for immediate-release (IR) guanfacine are not available.

              • clobazam

                guanfacine, clobazam. Other (see comment). Use Caution/Monitor. Comment: Concomitant administration can increase the potential for CNS effects (e.g., increased sedation or respiratory depression).

                clobazam will decrease the level or effect of guanfacine by affecting hepatic/intestinal enzyme CYP3A4 metabolism. Modify Therapy/Monitor Closely. Strong or moderate CYP3A4 inducers significantly reduce guanfacine plasma concentrations and elimination half-life. If coadministered, more frequent dosing of the IR product may be required to achieve or maintain the desired hypotensive response. For patients with ADHD, FDA-approved labeling for ER guanfacine recommends that, if coadministered, doubling the recommended dose of guanfacine should be considered.

              • clonidine

                clonidine, guanfacine. Either increases toxicity of the other by pharmacodynamic synergism. Use Caution/Monitor. Sympatholytic action may worsen sinus node dysfunction and atrioventricular (AV) block.

              • clozapine

                guanfacine, clozapine. Mechanism: pharmacodynamic synergism. Use Caution/Monitor. Additive hypotensive effects; potential delirium.

                clozapine will increase the level or effect of guanfacine by affecting hepatic/intestinal enzyme CYP3A4 metabolism. Modify Therapy/Monitor Closely. Strong or moderate CYP3A4 inhibitors significantly increase guanfacine plasma concentrations. FDA-approved labeling for extended-release (ER) guanfacine recommends that, if coadministered, the guanfacine dosage should be decreased to half of the recommended dose. Specific recommendations for immediate-release (IR) guanfacine are not available.

              • conivaptan

                conivaptan will increase the level or effect of guanfacine by affecting hepatic/intestinal enzyme CYP3A4 metabolism. Modify Therapy/Monitor Closely. Strong or moderate CYP3A4 inhibitors significantly increase guanfacine plasma concentrations. FDA-approved labeling for extended-release (ER) guanfacine recommends that, if coadministered, the guanfacine dosage should be decreased to half of the recommended dose. Specific recommendations for immediate-release (IR) guanfacine are not available.

              • crizotinib

                crizotinib will increase the level or effect of guanfacine by affecting hepatic/intestinal enzyme CYP3A4 metabolism. Modify Therapy/Monitor Closely. Strong or moderate CYP3A4 inhibitors significantly increase guanfacine plasma concentrations. FDA-approved labeling for extended-release (ER) guanfacine recommends that, if coadministered, the guanfacine dosage should be decreased to half of the recommended dose. Specific recommendations for immediate-release (IR) guanfacine are not available.

              • cyclosporine

                cyclosporine will increase the level or effect of guanfacine by affecting hepatic/intestinal enzyme CYP3A4 metabolism. Modify Therapy/Monitor Closely. Strong or moderate CYP3A4 inhibitors significantly increase guanfacine plasma concentrations. FDA-approved labeling for extended-release (ER) guanfacine recommends that, if coadministered, the guanfacine dosage should be decreased to half of the recommended dose. Specific recommendations for immediate-release (IR) guanfacine are not available.

              • dabrafenib

                dabrafenib will decrease the level or effect of guanfacine by affecting hepatic/intestinal enzyme CYP3A4 metabolism. Modify Therapy/Monitor Closely. Strong or moderate CYP3A4 inducers significantly reduce guanfacine plasma concentrations and elimination half-life. If coadministered, more frequent dosing of the IR product may be required to achieve or maintain the desired hypotensive response. For patients with ADHD, FDA-approved labeling for ER guanfacine recommends that, if coadministered, doubling the recommended dose of guanfacine should be considered.

              • darunavir

                darunavir will increase the level or effect of guanfacine by affecting hepatic/intestinal enzyme CYP3A4 metabolism. Modify Therapy/Monitor Closely. Strong or moderate CYP3A4 inhibitors significantly increase guanfacine plasma concentrations. FDA-approved labeling for extended-release (ER) guanfacine recommends that, if coadministered, the guanfacine dosage should be decreased to half of the recommended dose. Specific recommendations for immediate-release (IR) guanfacine are not available.

              • desipramine

                desipramine will increase the level or effect of guanfacine by affecting hepatic/intestinal enzyme CYP3A4 metabolism. Modify Therapy/Monitor Closely. Strong or moderate CYP3A4 inhibitors significantly increase guanfacine plasma concentrations. FDA-approved labeling for extended-release (ER) guanfacine recommends that, if coadministered, the guanfacine dosage should be decreased to half of the recommended dose. Specific recommendations for immediate-release (IR) guanfacine are not available.

              • dexamethasone

                dexamethasone will decrease the level or effect of guanfacine by affecting hepatic/intestinal enzyme CYP3A4 metabolism. Modify Therapy/Monitor Closely. Strong or moderate CYP3A4 inducers significantly reduce guanfacine plasma concentrations and elimination half-life. If coadministered, more frequent dosing of the IR product may be required to achieve or maintain the desired hypotensive response. For patients with ADHD, FDA-approved labeling for ER guanfacine recommends that, if coadministered, doubling the recommended dose of guanfacine should be considered.

              • DHEA, herbal

                DHEA, herbal will increase the level or effect of guanfacine by affecting hepatic/intestinal enzyme CYP3A4 metabolism. Modify Therapy/Monitor Closely. Strong or moderate CYP3A4 inhibitors significantly increase guanfacine plasma concentrations. FDA-approved labeling for extended-release (ER) guanfacine recommends that, if coadministered, the guanfacine dosage should be decreased to half of the recommended dose. Specific recommendations for immediate-release (IR) guanfacine are not available.

              • diltiazem

                diltiazem will increase the level or effect of guanfacine by affecting hepatic/intestinal enzyme CYP3A4 metabolism. Modify Therapy/Monitor Closely. Reduce guanfacine ER dose by 50% when initiating concomitant therapy with a moderate CYP3A4 inhibitor. When discontinuing moderate CYP3A4 inhibitor, increase guanfacine dose to recommended dose range. Monitor for excessive guanfacine response (eg, hypotension, bradycardia, CNS depression).

              • doxycycline

                doxycycline will increase the level or effect of guanfacine by affecting hepatic/intestinal enzyme CYP3A4 metabolism. Modify Therapy/Monitor Closely. Strong or moderate CYP3A4 inhibitors significantly increase guanfacine plasma concentrations. FDA-approved labeling for extended-release (ER) guanfacine recommends that, if coadministered, the guanfacine dosage should be decreased to half of the recommended dose. Specific recommendations for immediate-release (IR) guanfacine are not available.

              • dronedarone

                dronedarone will increase the level or effect of guanfacine by affecting hepatic/intestinal enzyme CYP3A4 metabolism. Modify Therapy/Monitor Closely. Strong or moderate CYP3A4 inhibitors significantly increase guanfacine plasma concentrations. FDA-approved labeling for extended-release (ER) guanfacine recommends that, if coadministered, the guanfacine dosage should be decreased to half of the recommended dose. Specific recommendations for immediate-release (IR) guanfacine are not available.

              • droperidol

                guanfacine, droperidol. Mechanism: pharmacodynamic synergism. Use Caution/Monitor. Additive hypotensive effects; potential delirium.

              • duvelisib

                duvelisib will increase the level or effect of guanfacine by affecting hepatic/intestinal enzyme CYP3A4 metabolism. Modify Therapy/Monitor Closely. Coadministration with duvelisib increases AUC of a sensitive CYP3A4 substrate which may increase the risk of toxicities of these drugs. Consider reducing the dose of the sensitive CYP3A4 substrate and monitor for signs of toxicities of the coadministered sensitive CYP3A substrate.

              • efavirenz

                efavirenz will decrease the level or effect of guanfacine by affecting hepatic/intestinal enzyme CYP3A4 metabolism. Modify Therapy/Monitor Closely. Strong or moderate CYP3A4 inducers significantly reduce guanfacine plasma concentrations and elimination half-life. If coadministered, more frequent dosing of the IR product may be required to achieve or maintain the desired hypotensive response. For patients with ADHD, FDA-approved labeling for ER guanfacine recommends that, if coadministered, doubling the recommended dose of guanfacine should be considered.

              • elagolix

                elagolix decreases levels of guanfacine by affecting hepatic/intestinal enzyme CYP3A4 metabolism. Modify Therapy/Monitor Closely. Elagolix is a weak-to-moderate CYP3A4 inducer. Monitor CYP3A substrates if coadministered. Consider increasing CYP3A substrate dose if needed.

              • elvitegravir/cobicistat/emtricitabine/tenofovir DF

                elvitegravir/cobicistat/emtricitabine/tenofovir DF increases levels of guanfacine by affecting hepatic/intestinal enzyme CYP3A4 metabolism. Modify Therapy/Monitor Closely. Strong or moderate CYP3A4 inhibitors significantly increase guanfacine plasma concentrations. FDA-approved labeling for extended-release (ER) guanfacine recommends that, if coadministered, the guanfacine dosage should be decreased to half of the recommended dose. Specific recommendations for immediate-release (IR) guanfacine are not available. .

              • encorafenib

                encorafenib, guanfacine. affecting hepatic/intestinal enzyme CYP3A4 metabolism. Use Caution/Monitor. Encorafenib both inhibits and induces CYP3A4 at clinically relevant plasma concentrations. Coadministration of encorafenib with sensitive CYP3A4 substrates may result in increased toxicity or decreased efficacy of these agents.

              • enzalutamide

                enzalutamide will decrease the level or effect of guanfacine by affecting hepatic/intestinal enzyme CYP3A4 metabolism. Modify Therapy/Monitor Closely. Strong or moderate CYP3A4 inducers significantly reduce guanfacine plasma concentrations and elimination half-life. If coadministered, more frequent dosing of the IR product may be required to achieve or maintain the desired hypotensive response. For patients with ADHD, FDA-approved labeling for ER guanfacine recommends that, if coadministered, doubling the recommended dose of guanfacine should be considered.

              • epinephrine inhaled

                guanfacine, epinephrine inhaled. Either increases effects of the other by sympathetic (adrenergic) effects, including increased blood pressure and heart rate. Use Caution/Monitor.

              • erythromycin base

                erythromycin base will increase the level or effect of guanfacine by affecting hepatic/intestinal enzyme CYP3A4 metabolism. Modify Therapy/Monitor Closely. Strong or moderate CYP3A4 inhibitors significantly increase guanfacine plasma concentrations. FDA-approved labeling for extended-release (ER) guanfacine recommends that, if coadministered, the guanfacine dosage should be decreased to half of the recommended dose. Specific recommendations for immediate-release (IR) guanfacine are not available.

              • erythromycin ethylsuccinate

                erythromycin ethylsuccinate will increase the level or effect of guanfacine by affecting hepatic/intestinal enzyme CYP3A4 metabolism. Modify Therapy/Monitor Closely. Strong or moderate CYP3A4 inhibitors significantly increase guanfacine plasma concentrations. FDA-approved labeling for extended-release (ER) guanfacine recommends that, if coadministered, the guanfacine dosage should be decreased to half of the recommended dose. Specific recommendations for immediate-release (IR) guanfacine are not available.

              • erythromycin lactobionate

                erythromycin lactobionate will increase the level or effect of guanfacine by affecting hepatic/intestinal enzyme CYP3A4 metabolism. Modify Therapy/Monitor Closely. Strong or moderate CYP3A4 inhibitors significantly increase guanfacine plasma concentrations. FDA-approved labeling for extended-release (ER) guanfacine recommends that, if coadministered, the guanfacine dosage should be decreased to half of the recommended dose. Specific recommendations for immediate-release (IR) guanfacine are not available.

              • erythromycin stearate

                erythromycin stearate will increase the level or effect of guanfacine by affecting hepatic/intestinal enzyme CYP3A4 metabolism. Modify Therapy/Monitor Closely. Strong or moderate CYP3A4 inhibitors significantly increase guanfacine plasma concentrations. FDA-approved labeling for extended-release (ER) guanfacine recommends that, if coadministered, the guanfacine dosage should be decreased to half of the recommended dose. Specific recommendations for immediate-release (IR) guanfacine are not available.

              • esketamine intranasal

                esketamine intranasal, guanfacine. Either increases toxicity of the other by sedation. Use Caution/Monitor.

                esketamine intranasal, guanfacine. Either increases toxicity of the other by sympathetic (adrenergic) effects, including increased blood pressure and heart rate. Use Caution/Monitor. Closely monitor blood pressure with concomitant use of esketamine nasal with stimulants. .

              • eslicarbazepine acetate

                eslicarbazepine acetate will decrease the level or effect of guanfacine by affecting hepatic/intestinal enzyme CYP3A4 metabolism. Modify Therapy/Monitor Closely. Strong or moderate CYP3A4 inducers significantly reduce guanfacine plasma concentrations and elimination half-life. If coadministered, more frequent dosing of the IR product may be required to achieve or maintain the desired hypotensive response. For patients with ADHD, FDA-approved labeling for ER guanfacine recommends that, if coadministered, doubling the recommended dose of guanfacine should be considered.

              • etravirine

                etravirine will decrease the level or effect of guanfacine by affecting hepatic/intestinal enzyme CYP3A4 metabolism. Modify Therapy/Monitor Closely. Strong or moderate CYP3A4 inducers significantly reduce guanfacine plasma concentrations and elimination half-life. If coadministered, more frequent dosing of the IR product may be required to achieve or maintain the desired hypotensive response. For patients with ADHD, FDA-approved labeling for ER guanfacine recommends that, if coadministered, doubling the recommended dose of guanfacine should be considered.

              • fedratinib

                fedratinib will increase the level or effect of guanfacine by affecting hepatic/intestinal enzyme CYP3A4 metabolism. Use Caution/Monitor. Adjust dose of drugs that are CYP3A4 substrates as necessary.

              • fluconazole

                fluconazole will increase the level or effect of guanfacine by affecting hepatic/intestinal enzyme CYP3A4 metabolism. Modify Therapy/Monitor Closely. Strong or moderate CYP3A4 inhibitors significantly increase guanfacine plasma concentrations. FDA-approved labeling for extended-release (ER) guanfacine recommends that, if coadministered, the guanfacine dosage should be decreased to half of the recommended dose. Specific recommendations for immediate-release (IR) guanfacine are not available.

              • fluphenazine

                guanfacine, fluphenazine. Mechanism: pharmacodynamic synergism. Use Caution/Monitor. Additive hypotensive effects; potential delirium.

              • fluvoxamine

                fluvoxamine will increase the level or effect of guanfacine by affecting hepatic/intestinal enzyme CYP3A4 metabolism. Modify Therapy/Monitor Closely. If coadministered with extended release, reduce guanfacine dosage in half of recommended dose; specific recommendation for immediate release form not available

              • fosamprenavir

                fosamprenavir will increase the level or effect of guanfacine by affecting hepatic/intestinal enzyme CYP3A4 metabolism. Modify Therapy/Monitor Closely. Strong or moderate CYP3A4 inhibitors significantly increase guanfacine plasma concentrations. FDA-approved labeling for extended-release (ER) guanfacine recommends that, if coadministered, the guanfacine dosage should be decreased to half of the recommended dose. Specific recommendations for immediate-release (IR) guanfacine are not available.

              • fosphenytoin

                fosphenytoin will decrease the level or effect of guanfacine by affecting hepatic/intestinal enzyme CYP3A4 metabolism. Modify Therapy/Monitor Closely. Strong or moderate CYP3A4 inducers significantly reduce guanfacine plasma concentrations and elimination half-life. If coadministered, more frequent dosing of the IR product may be required to achieve or maintain the desired hypotensive response. For patients with ADHD, FDA-approved labeling for ER guanfacine recommends that, if coadministered, doubling the recommended dose of guanfacine should be considered.

              • grapefruit

                grapefruit will increase the level or effect of guanfacine by affecting hepatic/intestinal enzyme CYP3A4 metabolism. Modify Therapy/Monitor Closely. Strong or moderate CYP3A4 inhibitors significantly increase guanfacine plasma concentrations. FDA-approved labeling for extended-release (ER) guanfacine recommends that, if coadministered, the guanfacine dosage should be decreased to half of the recommended dose. Specific recommendations for immediate-release (IR) guanfacine are not available.

              • haloperidol

                guanfacine, haloperidol. Mechanism: pharmacodynamic synergism. Use Caution/Monitor. Additive hypotensive effects; potential delirium.

                haloperidol will increase the level or effect of guanfacine by affecting hepatic/intestinal enzyme CYP3A4 metabolism. Modify Therapy/Monitor Closely. Strong or moderate CYP3A4 inhibitors significantly increase guanfacine plasma concentrations. FDA-approved labeling for extended-release (ER) guanfacine recommends that, if coadministered, the guanfacine dosage should be decreased to half of the recommended dose. Specific recommendations for immediate-release (IR) guanfacine are not available.

              • idelalisib

                idelalisib will increase the level or effect of guanfacine by affecting hepatic/intestinal enzyme CYP3A4 metabolism. Modify Therapy/Monitor Closely. Strong or moderate CYP3A4 inhibitors significantly increase guanfacine plasma concentrations. FDA-approved labeling for extended-release (ER) guanfacine recommends that, if coadministered, the guanfacine dosage should be decreased to half of the recommended dose. Specific recommendations for immediate-release (IR) guanfacine are not available.

              • iloperidone

                guanfacine, iloperidone. Mechanism: pharmacodynamic synergism. Use Caution/Monitor. Additive hypotensive effects; potential delirium.

                iloperidone increases levels of guanfacine by affecting hepatic/intestinal enzyme CYP3A4 metabolism. Modify Therapy/Monitor Closely. Strong or moderate CYP3A4 inhibitors significantly increase guanfacine plasma concentrations. FDA-approved labeling for extended-release (ER) guanfacine recommends that, if coadministered, the guanfacine dosage should be decreased to half of the recommended dose. Specific recommendations for immediate-release (IR) guanfacine are not available. .

              • imatinib

                imatinib will increase the level or effect of guanfacine by affecting hepatic/intestinal enzyme CYP3A4 metabolism. Modify Therapy/Monitor Closely. Strong or moderate CYP3A4 inhibitors significantly increase guanfacine plasma concentrations. FDA-approved labeling for extended-release (ER) guanfacine recommends that, if coadministered, the guanfacine dosage should be decreased to half of the recommended dose. Specific recommendations for immediate-release (IR) guanfacine are not available.

              • indinavir

                indinavir will increase the level or effect of guanfacine by affecting hepatic/intestinal enzyme CYP3A4 metabolism. Modify Therapy/Monitor Closely. Strong or moderate CYP3A4 inhibitors significantly increase guanfacine plasma concentrations. FDA-approved labeling for extended-release (ER) guanfacine recommends that, if coadministered, the guanfacine dosage should be decreased to half of the recommended dose. Specific recommendations for immediate-release (IR) guanfacine are not available.

              • isoniazid

                isoniazid will increase the level or effect of guanfacine by affecting hepatic/intestinal enzyme CYP3A4 metabolism. Modify Therapy/Monitor Closely. Strong or moderate CYP3A4 inhibitors significantly increase guanfacine plasma concentrations. FDA-approved labeling for extended-release (ER) guanfacine recommends that, if coadministered, the guanfacine dosage should be decreased to half of the recommended dose. Specific recommendations for immediate-release (IR) guanfacine are not available.

              • istradefylline

                istradefylline will increase the level or effect of guanfacine by affecting hepatic/intestinal enzyme CYP3A4 metabolism. Use Caution/Monitor. Istradefylline 40 mg/day increased peak levels and AUC of CYP3A4 substrates in clinical trials. This effect was not observed with istradefylline 20 mg/day. Consider dose reduction of sensitive CYP3A4 substrates.

              • itraconazole

                itraconazole will increase the level or effect of guanfacine by affecting hepatic/intestinal enzyme CYP3A4 metabolism. Modify Therapy/Monitor Closely. For extended-release (ER) guanfacine, if coadministered, decrease the guanfacine dosage to half of the recommended dose. Specific recommendations for immediate-release (IR) guanfacine are not available.

              • ketoconazole

                ketoconazole will increase the level or effect of guanfacine by affecting hepatic/intestinal enzyme CYP3A4 metabolism. Modify Therapy/Monitor Closely. Strong or moderate CYP3A4 inhibitors significantly increase guanfacine plasma concentrations. FDA-approved labeling for extended-release (ER) guanfacine recommends that, if coadministered, the guanfacine dosage should be decreased to half of the recommended dose. Specific recommendations for immediate-release (IR) guanfacine are not available.

              • lapatinib

                lapatinib will increase the level or effect of guanfacine by affecting hepatic/intestinal enzyme CYP3A4 metabolism. Modify Therapy/Monitor Closely. Strong or moderate CYP3A4 inhibitors significantly increase guanfacine plasma concentrations. FDA-approved labeling for extended-release (ER) guanfacine recommends that, if coadministered, the guanfacine dosage should be decreased to half of the recommended dose. Specific recommendations for immediate-release (IR) guanfacine are not available.

              • lasmiditan

                lasmiditan, guanfacine. Either increases effects of the other by sedation. Use Caution/Monitor. Coadministration of lasmiditan and other CNS depressant drugs, including alcohol have not been evaluated in clinical studies. Lasmiditan may cause sedation, as well as other cognitive and/or neuropsychiatric adverse reactions.

              • lemborexant

                lemborexant, guanfacine. Either increases effects of the other by sedation. Modify Therapy/Monitor Closely. Dosage adjustment may be necessary if lemborexant is coadministered with other CNS depressants because of potentially additive effects.

              • levodopa

                levodopa increases effects of guanfacine by pharmacodynamic synergism. Use Caution/Monitor. Consider decreasing dosage of antihypertensive agent.

              • lopinavir

                lopinavir will increase the level or effect of guanfacine by affecting hepatic/intestinal enzyme CYP3A4 metabolism. Modify Therapy/Monitor Closely. Strong or moderate CYP3A4 inhibitors significantly increase guanfacine plasma concentrations. FDA-approved labeling for extended-release (ER) guanfacine recommends that, if coadministered, the guanfacine dosage should be decreased to half of the recommended dose. Specific recommendations for immediate-release (IR) guanfacine are not available.

              • loxapine

                guanfacine, loxapine. Mechanism: pharmacodynamic synergism. Use Caution/Monitor. Additive hypotensive effects; potential delirium.

              • loxapine inhaled

                guanfacine, loxapine inhaled. Mechanism: pharmacodynamic synergism. Use Caution/Monitor. Additive hypotensive effects; potential delirium.

              • lumacaftor/ivacaftor

                lumacaftor/ivacaftor will decrease the level or effect of guanfacine by affecting hepatic/intestinal enzyme CYP3A4 metabolism. Modify Therapy/Monitor Closely. Strong or moderate CYP3A4 inducers significantly reduce guanfacine plasma concentrations and elimination half-life. If coadministered, more frequent dosing of the IR product may be required to achieve or maintain the desired hypotensive response. For patients with ADHD, FDA-approved labeling for ER guanfacine recommends that, if coadministered, doubling the recommended dose of guanfacine should be considered.

              • lurasidone

                lurasidone increases effects of guanfacine by Other (see comment). Use Caution/Monitor. Comment: Potential for increased risk of hypotension with concurrent use. Monitor blood pressure and adjust dose of antihypertensive agent as needed.

                lurasidone, guanfacine. Either increases toxicity of the other by sedation. Use Caution/Monitor. Potential for increased CNS depressant effects when used concurrently; monitor for increased adverse effects and toxicity.

              • metronidazole

                metronidazole will increase the level or effect of guanfacine by affecting hepatic/intestinal enzyme CYP3A4 metabolism. Modify Therapy/Monitor Closely. Strong or moderate CYP3A4 inhibitors significantly increase guanfacine plasma concentrations. FDA-approved labeling for extended-release (ER) guanfacine recommends that, if coadministered, the guanfacine dosage should be decreased to half of the recommended dose. Specific recommendations for immediate-release (IR) guanfacine are not available.

              • midazolam intranasal

                midazolam intranasal, guanfacine. Either increases toxicity of the other by pharmacodynamic synergism. Modify Therapy/Monitor Closely. Concomitant use of barbiturates, alcohol, or other CNS depressants may increase the risk of hypoventilation, airway obstruction, desaturation, or apnea and may contribute to profound and/or prolonged drug effect.

              • mitotane

                mitotane decreases levels of guanfacine by affecting hepatic/intestinal enzyme CYP3A4 metabolism. Modify Therapy/Monitor Closely. Strong or moderate CYP3A4 inducers significantly reduce guanfacine plasma concentrations and elimination half-life. If coadministered, more frequent dosing of the IR product may be required to achieve or maintain the desired hypotensive response. For patients with ADHD, FDA-approved labeling for ER guanfacine recommends that, if coadministered, doubling the recommended dose of guanfacine should be considered.

              • modafinil

                modafinil will decrease the level or effect of guanfacine by affecting hepatic/intestinal enzyme CYP3A4 metabolism. Modify Therapy/Monitor Closely. Strong or moderate CYP3A4 inducers significantly reduce guanfacine plasma concentrations and elimination half-life. If coadministered, more frequent dosing of the IR product may be required to achieve or maintain the desired hypotensive response. For patients with ADHD, FDA-approved labeling for ER guanfacine recommends that, if coadministered, doubling the recommended dose of guanfacine should be considered.

              • nadolol

                nadolol, guanfacine. Mechanism: pharmacodynamic synergism. Use Caution/Monitor. Non selective beta blocker administration during withdrawal from centrally acting alpha agonists may result in rebound hypertension.

              • nafcillin

                nafcillin will decrease the level or effect of guanfacine by affecting hepatic/intestinal enzyme CYP3A4 metabolism. Modify Therapy/Monitor Closely. Strong or moderate CYP3A4 inducers significantly reduce guanfacine plasma concentrations and elimination half-life. If coadministered, more frequent dosing of the IR product may be required to achieve or maintain the desired hypotensive response. For patients with ADHD, FDA-approved labeling for ER guanfacine recommends that, if coadministered, doubling the recommended dose of guanfacine should be considered.

              • nefazodone

                nefazodone will increase the level or effect of guanfacine by affecting hepatic/intestinal enzyme CYP3A4 metabolism. Modify Therapy/Monitor Closely. Strong or moderate CYP3A4 inhibitors significantly increase guanfacine plasma concentrations. FDA-approved labeling for extended-release (ER) guanfacine recommends that, if coadministered, the guanfacine dosage should be decreased to half of the recommended dose. Specific recommendations for immediate-release (IR) guanfacine are not available.

              • nelfinavir

                nelfinavir will increase the level or effect of guanfacine by affecting hepatic/intestinal enzyme CYP3A4 metabolism. Modify Therapy/Monitor Closely. Strong or moderate CYP3A4 inhibitors significantly increase guanfacine plasma concentrations. FDA-approved labeling for extended-release (ER) guanfacine recommends that, if coadministered, the guanfacine dosage should be decreased to half of the recommended dose. Specific recommendations for immediate-release (IR) guanfacine are not available.

              • netupitant/palonosetron

                netupitant/palonosetron will increase the level or effect of guanfacine by affecting hepatic/intestinal enzyme CYP3A4 metabolism. Modify Therapy/Monitor Closely. Strong or moderate CYP3A4 inhibitors significantly increase guanfacine plasma concentrations. FDA-approved labeling for extended-release (ER) guanfacine recommends that, if coadministered, the guanfacine dosage should be decreased to half of the recommended dose. Specific recommendations for immediate-release (IR) guanfacine are not available.

              • nevirapine

                nevirapine will decrease the level or effect of guanfacine by affecting hepatic/intestinal enzyme CYP3A4 metabolism. Modify Therapy/Monitor Closely. Strong or moderate CYP3A4 inducers significantly reduce guanfacine plasma concentrations and elimination half-life. If coadministered, more frequent dosing of the IR product may be required to achieve or maintain the desired hypotensive response. For patients with ADHD, FDA-approved labeling for ER guanfacine recommends that, if coadministered, doubling the recommended dose of guanfacine should be considered.

              • nicardipine

                nicardipine will increase the level or effect of guanfacine by affecting hepatic/intestinal enzyme CYP3A4 metabolism. Modify Therapy/Monitor Closely. Strong or moderate CYP3A4 inhibitors significantly increase guanfacine plasma concentrations. FDA-approved labeling for extended-release (ER) guanfacine recommends that, if coadministered, the guanfacine dosage should be decreased to half of the recommended dose. Specific recommendations for immediate-release (IR) guanfacine are not available.

              • nilotinib

                nilotinib will increase the level or effect of guanfacine by affecting hepatic/intestinal enzyme CYP3A4 metabolism. Modify Therapy/Monitor Closely. Strong or moderate CYP3A4 inhibitors significantly increase guanfacine plasma concentrations. FDA-approved labeling for extended-release (ER) guanfacine recommends that, if coadministered, the guanfacine dosage should be decreased to half of the recommended dose. Specific recommendations for immediate-release (IR) guanfacine are not available.

              • nitroglycerin rectal

                nitroglycerin rectal, guanfacine. Either increases effects of the other by pharmacodynamic synergism. Use Caution/Monitor. Observe for possible additive hypotensive effects during concomitant use. .

              • nitroprusside sodium

                nitroprusside sodium, guanfacine. Either increases effects of the other by pharmacodynamic synergism. Use Caution/Monitor. Additive hypotensive effects.

              • olanzapine

                guanfacine, olanzapine. Mechanism: pharmacodynamic synergism. Use Caution/Monitor. Additive hypotensive effects; potential delirium.

              • oxcarbazepine

                oxcarbazepine will decrease the level or effect of guanfacine by affecting hepatic/intestinal enzyme CYP3A4 metabolism. Modify Therapy/Monitor Closely. Strong or moderate CYP3A4 inducers significantly reduce guanfacine plasma concentrations and elimination half-life. If coadministered, more frequent dosing of the IR product may be required to achieve or maintain the desired hypotensive response. For patients with ADHD, FDA-approved labeling for ER guanfacine recommends that, if coadministered, doubling the recommended dose of guanfacine should be considered.

              • paliperidone

                guanfacine, paliperidone. Mechanism: pharmacodynamic synergism. Use Caution/Monitor. Additive hypotensive effects; potential delirium.

              • pentobarbital

                pentobarbital will decrease the level or effect of guanfacine by affecting hepatic/intestinal enzyme CYP3A4 metabolism. Modify Therapy/Monitor Closely. Strong or moderate CYP3A4 inducers significantly reduce guanfacine plasma concentrations and elimination half-life. If coadministered, more frequent dosing of the IR product may be required to achieve or maintain the desired hypotensive response. For patients with ADHD, FDA-approved labeling for ER guanfacine recommends that, if coadministered, doubling the recommended dose of guanfacine should be considered.

              • perphenazine

                guanfacine, perphenazine. Mechanism: pharmacodynamic synergism. Use Caution/Monitor. Additive hypotensive effects; potential delirium.

              • phenobarbital

                phenobarbital will decrease the level or effect of guanfacine by affecting hepatic/intestinal enzyme CYP3A4 metabolism. Modify Therapy/Monitor Closely. Strong or moderate CYP3A4 inducers significantly reduce guanfacine plasma concentrations and elimination half-life. If coadministered, more frequent dosing of the IR product may be required to achieve or maintain the desired hypotensive response. For patients with ADHD, FDA-approved labeling for ER guanfacine recommends that, if coadministered, doubling the recommended dose of guanfacine should be considered.

              • phenytoin

                phenytoin will decrease the level or effect of guanfacine by affecting hepatic/intestinal enzyme CYP3A4 metabolism. Modify Therapy/Monitor Closely. Strong or moderate CYP3A4 inducers significantly reduce guanfacine plasma concentrations and elimination half-life. If coadministered, more frequent dosing of the IR product may be required to achieve or maintain the desired hypotensive response. For patients with ADHD, FDA-approved labeling for ER guanfacine recommends that, if coadministered, doubling the recommended dose of guanfacine should be considered.

              • pimozide

                guanfacine, pimozide. Mechanism: pharmacodynamic synergism. Use Caution/Monitor. Additive hypotensive effects; potential delirium.

              • pindolol

                pindolol, guanfacine. Mechanism: pharmacodynamic synergism. Use Caution/Monitor. Non selective beta blocker administration during withdrawal from centrally acting alpha agonists may result in rebound hypertension.

              • posaconazole

                posaconazole will increase the level or effect of guanfacine by affecting hepatic/intestinal enzyme CYP3A4 metabolism. Modify Therapy/Monitor Closely. Strong or moderate CYP3A4 inhibitors significantly increase guanfacine plasma concentrations. FDA-approved labeling for extended-release (ER) guanfacine recommends that, if coadministered, the guanfacine dosage should be decreased to half of the recommended dose. Specific recommendations for immediate-release (IR) guanfacine are not available.

              • primidone

                primidone will decrease the level or effect of guanfacine by affecting hepatic/intestinal enzyme CYP3A4 metabolism. Modify Therapy/Monitor Closely. Strong or moderate CYP3A4 inducers significantly reduce guanfacine plasma concentrations and elimination half-life. If coadministered, more frequent dosing of the IR product may be required to achieve or maintain the desired hypotensive response. For patients with ADHD, FDA-approved labeling for ER guanfacine recommends that, if coadministered, doubling the recommended dose of guanfacine should be considered.

              • prochlorperazine

                guanfacine, prochlorperazine. Mechanism: pharmacodynamic synergism. Use Caution/Monitor. Additive hypotensive effects; potential delirium.

              • promethazine

                guanfacine, promethazine. Mechanism: pharmacodynamic synergism. Use Caution/Monitor. Additive hypotensive effects; potential delirium.

              • propranolol

                propranolol, guanfacine. Mechanism: pharmacodynamic synergism. Use Caution/Monitor. Non selective beta blocker administration during withdrawal from centrally acting alpha agonists may result in rebound hypertension.

              • quetiapine

                guanfacine, quetiapine. Mechanism: pharmacodynamic synergism. Use Caution/Monitor. Additive hypotensive effects; potential delirium.

              • quinupristin/dalfopristin

                quinupristin/dalfopristin will increase the level or effect of guanfacine by affecting hepatic/intestinal enzyme CYP3A4 metabolism. Modify Therapy/Monitor Closely. Strong or moderate CYP3A4 inhibitors significantly increase guanfacine plasma concentrations. FDA-approved labeling for extended-release (ER) guanfacine recommends that, if coadministered, the guanfacine dosage should be decreased to half of the recommended dose. Specific recommendations for immediate-release (IR) guanfacine are not available.

              • ribociclib

                ribociclib will increase the level or effect of guanfacine by affecting hepatic/intestinal enzyme CYP3A4 metabolism. Modify Therapy/Monitor Closely.

              • rifabutin

                rifabutin will decrease the level or effect of guanfacine by affecting hepatic/intestinal enzyme CYP3A4 metabolism. Modify Therapy/Monitor Closely. Strong or moderate CYP3A4 inducers significantly reduce guanfacine plasma concentrations and elimination half-life. If coadministered, more frequent dosing of the IR product may be required to achieve or maintain the desired hypotensive response. For patients with ADHD, FDA-approved labeling for ER guanfacine recommends that, if coadministered, doubling the recommended dose of guanfacine should be considered.

              • rifampin

                rifampin will decrease the level or effect of guanfacine by affecting hepatic/intestinal enzyme CYP3A4 metabolism. Modify Therapy/Monitor Closely. Strong or moderate CYP3A4 inducers significantly reduce guanfacine plasma concentrations and elimination half-life. If coadministered, more frequent dosing of the IR product may be required to achieve or maintain the desired hypotensive response. For patients with ADHD, FDA-approved labeling for ER guanfacine recommends that, if coadministered, doubling the recommended dose of guanfacine should be considered.

              • rifapentine

                rifapentine will decrease the level or effect of guanfacine by affecting hepatic/intestinal enzyme CYP3A4 metabolism. Modify Therapy/Monitor Closely. Strong or moderate CYP3A4 inducers significantly reduce guanfacine plasma concentrations and elimination half-life. If coadministered, more frequent dosing of the IR product may be required to achieve or maintain the desired hypotensive response. For patients with ADHD, FDA-approved labeling for ER guanfacine recommends that, if coadministered, doubling the recommended dose of guanfacine should be considered.

              • risperidone

                guanfacine, risperidone. Mechanism: pharmacodynamic synergism. Use Caution/Monitor. Additive hypotensive effects; potential delirium.

              • ritonavir

                ritonavir will increase the level or effect of guanfacine by affecting hepatic/intestinal enzyme CYP3A4 metabolism. Modify Therapy/Monitor Closely. Strong or moderate CYP3A4 inhibitors significantly increase guanfacine plasma concentrations. FDA-approved labeling for extended-release (ER) guanfacine recommends that, if coadministered, the guanfacine dosage should be decreased to half of the recommended dose. Specific recommendations for immediate-release (IR) guanfacine are not available.

              • rucaparib

                rucaparib will increase the level or effect of guanfacine by affecting hepatic/intestinal enzyme CYP3A4 metabolism. Modify Therapy/Monitor Closely. Adjust dosage of CYP3A4 substrates, if clinically indicated.

              • saquinavir

                saquinavir will increase the level or effect of guanfacine by affecting hepatic/intestinal enzyme CYP3A4 metabolism. Modify Therapy/Monitor Closely. Strong or moderate CYP3A4 inhibitors significantly increase guanfacine plasma concentrations. FDA-approved labeling for extended-release (ER) guanfacine recommends that, if coadministered, the guanfacine dosage should be decreased to half of the recommended dose. Specific recommendations for immediate-release (IR) guanfacine are not available.

              • schisandra

                schisandra will increase the level or effect of guanfacine by affecting hepatic/intestinal enzyme CYP3A4 metabolism. Modify Therapy/Monitor Closely. Strong or moderate CYP3A4 inhibitors significantly increase guanfacine plasma concentrations. FDA-approved labeling for extended-release (ER) guanfacine recommends that, if coadministered, the guanfacine dosage should be decreased to half of the recommended dose. Specific recommendations for immediate-release (IR) guanfacine are not available.

              • secobarbital

                secobarbital will decrease the level or effect of guanfacine by affecting hepatic/intestinal enzyme CYP3A4 metabolism. Modify Therapy/Monitor Closely. Strong or moderate CYP3A4 inducers significantly reduce guanfacine plasma concentrations and elimination half-life. If coadministered, more frequent dosing of the IR product may be required to achieve or maintain the desired hypotensive response. For patients with ADHD, FDA-approved labeling for ER guanfacine recommends that, if coadministered, doubling the recommended dose of guanfacine should be considered.

              • sertraline

                sertraline will increase the level or effect of guanfacine by affecting hepatic/intestinal enzyme CYP3A4 metabolism. Modify Therapy/Monitor Closely. Strong or moderate CYP3A4 inhibitors significantly increase guanfacine plasma concentrations. FDA-approved labeling for extended-release (ER) guanfacine recommends that, if coadministered, the guanfacine dosage should be decreased to half of the recommended dose. Specific recommendations for immediate-release (IR) guanfacine are not available.

              • sofosbuvir/velpatasvir

                sofosbuvir/velpatasvir will increase the level or effect of guanfacine by affecting hepatic/intestinal enzyme CYP3A4 metabolism. Modify Therapy/Monitor Closely. Strong or moderate CYP3A4 inhibitors significantly increase guanfacine plasma concentrations. FDA-approved labeling for extended-release (ER) guanfacine recommends that, if coadministered, the guanfacine dosage should be decreased to half of the recommended dose. Specific recommendations for immediate-release (IR) guanfacine are not available.

              • St John's Wort

                St John's Wort will decrease the level or effect of guanfacine by affecting hepatic/intestinal enzyme CYP3A4 metabolism. Modify Therapy/Monitor Closely. Strong or moderate CYP3A4 inducers significantly reduce guanfacine plasma concentrations and elimination half-life. If coadministered, more frequent dosing of the IR product may be required to achieve or maintain the desired hypotensive response. For patients with ADHD, FDA-approved labeling for ER guanfacine recommends that, if coadministered, doubling the recommended dose of guanfacine should be considered.

              • stiripentol

                stiripentol, guanfacine. affecting hepatic/intestinal enzyme CYP3A4 metabolism. Modify Therapy/Monitor Closely. Stiripentol is a CYP3A4 inhibitor and inducer. Monitor CYP3A4 substrates coadministered with stiripentol for increased or decreased effects. CYP3A4 substrates may require dosage adjustment.

                stiripentol, guanfacine. Either increases effects of the other by sedation. Use Caution/Monitor. Concomitant use stiripentol with other CNS depressants, including alcohol, may increase the risk of sedation and somnolence.

              • tadalafil

                tadalafil increases effects of guanfacine by pharmacodynamic synergism. Use Caution/Monitor. Risk of hypotension.

              • tazemetostat

                tazemetostat will decrease the level or effect of guanfacine by affecting hepatic/intestinal enzyme CYP3A4 metabolism. Use Caution/Monitor.

              • tecovirimat

                tecovirimat will decrease the level or effect of guanfacine by affecting hepatic/intestinal enzyme CYP3A4 metabolism. Use Caution/Monitor. Tecovirimat is a weak CYP3A4 inducer. Monitor sensitive CYP3A4 substrates for effectiveness if coadministered.

              • thioridazine

                guanfacine, thioridazine. Mechanism: pharmacodynamic synergism. Use Caution/Monitor. Additive hypotensive effects; potential delirium.

              • thiothixene

                guanfacine, thiothixene. Mechanism: pharmacodynamic synergism. Use Caution/Monitor. Additive hypotensive effects; potential delirium.

              • timolol

                timolol, guanfacine. Mechanism: pharmacodynamic synergism. Use Caution/Monitor. Non selective beta blocker administration during withdrawal from centrally acting alpha agonists may result in rebound hypertension.

              • tipranavir

                tipranavir will increase the level or effect of guanfacine by affecting hepatic/intestinal enzyme CYP3A4 metabolism. Modify Therapy/Monitor Closely. Strong or moderate CYP3A4 inhibitors significantly increase guanfacine plasma concentrations. FDA-approved labeling for extended-release (ER) guanfacine recommends that, if coadministered, the guanfacine dosage should be decreased to half of the recommended dose. Specific recommendations for immediate-release (IR) guanfacine are not available.

              • trifluoperazine

                guanfacine, trifluoperazine. Mechanism: pharmacodynamic synergism. Use Caution/Monitor. Additive hypotensive effects; potential delirium.

              • valproic acid

                guanfacine increases levels of valproic acid by unknown mechanism. Use Caution/Monitor. Both 3-hydroxy guanfacine (metabolite) and valproic acid are metabolized by glucuronidation, possibly resulting in competitive inhibition.

              • verapamil

                verapamil will increase the level or effect of guanfacine by affecting hepatic/intestinal enzyme CYP3A4 metabolism. Modify Therapy/Monitor Closely. Strong or moderate CYP3A4 inhibitors significantly increase guanfacine plasma concentrations. FDA-approved labeling for extended-release (ER) guanfacine recommends that, if coadministered, the guanfacine dosage should be decreased to half of the recommended dose. Specific recommendations for immediate-release (IR) guanfacine are not available.

              • voriconazole

                voriconazole will increase the level or effect of guanfacine by affecting hepatic/intestinal enzyme CYP3A4 metabolism. Modify Therapy/Monitor Closely. Strong or moderate CYP3A4 inhibitors significantly increase guanfacine plasma concentrations. FDA-approved labeling for extended-release (ER) guanfacine recommends that, if coadministered, the guanfacine dosage should be decreased to half of the recommended dose. Specific recommendations for immediate-release (IR) guanfacine are not available.

              • xipamide

                xipamide increases effects of guanfacine by pharmacodynamic synergism. Use Caution/Monitor.

              • ziprasidone

                guanfacine, ziprasidone. Mechanism: pharmacodynamic synergism. Use Caution/Monitor. Additive hypotensive effects; potential delirium.

              • zotepine

                guanfacine, zotepine. Mechanism: pharmacodynamic synergism. Use Caution/Monitor. Additive hypotensive effects; potential delirium.

              Minor (43)

              • acarbose

                guanfacine decreases effects of acarbose by pharmacodynamic antagonism. Minor/Significance Unknown. Diminished symptoms of hypoglycemia.

                guanfacine, acarbose. Other (see comment). Minor/Significance Unknown. Comment: Decreased symptoms of hypoglycemia. Mechanism: decreased hypoglycemia induced catecholamine production.

              • acebutolol

                acebutolol, guanfacine. Mechanism: pharmacodynamic synergism. Minor/Significance Unknown. Selective beta blocker administration during withdrawal from centrally acting alpha agonists may result in rebound hypertension.

              • agrimony

                agrimony increases effects of guanfacine by pharmacodynamic synergism. Minor/Significance Unknown.

              • atenolol

                atenolol, guanfacine. Mechanism: pharmacodynamic synergism. Minor/Significance Unknown. Selective beta blocker administration during withdrawal from centrally acting alpha agonists may result in rebound hypertension.

              • betaxolol

                betaxolol, guanfacine. Mechanism: pharmacodynamic synergism. Minor/Significance Unknown. Selective beta blocker administration during withdrawal from centrally acting alpha agonists may result in rebound hypertension.

              • bisoprolol

                bisoprolol, guanfacine. Mechanism: pharmacodynamic synergism. Minor/Significance Unknown. Selective beta blocker administration during withdrawal from centrally acting alpha agonists may result in rebound hypertension.

              • brimonidine

                brimonidine increases effects of guanfacine by pharmacodynamic synergism. Minor/Significance Unknown.

              • celiprolol

                celiprolol, guanfacine. Mechanism: pharmacodynamic synergism. Minor/Significance Unknown. Selective beta blocker administration during withdrawal from centrally acting alpha agonists may result in rebound hypertension.

              • chlorpropamide

                guanfacine decreases effects of chlorpropamide by pharmacodynamic antagonism. Minor/Significance Unknown. Diminished symptoms of hypoglycemia.

                guanfacine, chlorpropamide. Other (see comment). Minor/Significance Unknown. Comment: Decreased symptoms of hypoglycemia. Mechanism: decreased hypoglycemia induced catecholamine production.

              • cornsilk

                cornsilk increases effects of guanfacine by pharmacodynamic synergism. Minor/Significance Unknown.

              • esmolol

                esmolol, guanfacine. Mechanism: pharmacodynamic synergism. Minor/Significance Unknown. Selective beta blocker administration during withdrawal from centrally acting alpha agonists may result in rebound hypertension.

              • forskolin

                forskolin increases effects of guanfacine by pharmacodynamic synergism. Minor/Significance Unknown.

              • glimepiride

                guanfacine decreases effects of glimepiride by pharmacodynamic antagonism. Minor/Significance Unknown. Diminished symptoms of hypoglycemia.

                guanfacine, glimepiride. Other (see comment). Minor/Significance Unknown. Comment: Decreased symptoms of hypoglycemia. Mechanism: decreased hypoglycemia induced catecholamine production.

              • glipizide

                guanfacine decreases effects of glipizide by pharmacodynamic antagonism. Minor/Significance Unknown. Diminished symptoms of hypoglycemia.

                guanfacine, glipizide. Other (see comment). Minor/Significance Unknown. Comment: Decreased symptoms of hypoglycemia. Mechanism: decreased hypoglycemia induced catecholamine production.

              • glyburide

                guanfacine decreases effects of glyburide by pharmacodynamic antagonism. Minor/Significance Unknown. Diminished symptoms of hypoglycemia.

                guanfacine, glyburide. Other (see comment). Minor/Significance Unknown. Comment: Decreased symptoms of hypoglycemia. Mechanism: decreased hypoglycemia induced catecholamine production.

              • insulin aspart

                guanfacine decreases effects of insulin aspart by pharmacodynamic antagonism. Minor/Significance Unknown. Diminished symptoms of hypoglycemia.

                guanfacine, insulin aspart. Other (see comment). Minor/Significance Unknown. Comment: Decreased symptoms of hypoglycemia. Mechanism: decreased hypoglycemia induced catecholamine production.

              • insulin detemir

                guanfacine, insulin detemir. Other (see comment). Minor/Significance Unknown. Comment: Decreased symptoms of hypoglycemia. Mechanism: decreased hypoglycemia induced catecholamine production.

                guanfacine decreases effects of insulin detemir by pharmacodynamic antagonism. Minor/Significance Unknown. Diminished symptoms of hypoglycemia.

              • insulin glargine

                guanfacine, insulin glargine. Other (see comment). Minor/Significance Unknown. Comment: Decreased symptoms of hypoglycemia. Mechanism: decreased hypoglycemia induced catecholamine production.

                guanfacine decreases effects of insulin glargine by pharmacodynamic antagonism. Minor/Significance Unknown. Diminished symptoms of hypoglycemia.

              • insulin glulisine

                guanfacine, insulin glulisine. Other (see comment). Minor/Significance Unknown. Comment: Decreased symptoms of hypoglycemia. Mechanism: decreased hypoglycemia induced catecholamine production.

                guanfacine decreases effects of insulin glulisine by pharmacodynamic antagonism. Minor/Significance Unknown. Diminished symptoms of hypoglycemia.

              • insulin lispro

                guanfacine decreases effects of insulin lispro by pharmacodynamic antagonism. Minor/Significance Unknown. Diminished symptoms of hypoglycemia.

                guanfacine, insulin lispro. Other (see comment). Minor/Significance Unknown. Comment: Decreased symptoms of hypoglycemia. Mechanism: decreased hypoglycemia induced catecholamine production.

              • insulin NPH

                guanfacine, insulin NPH. Other (see comment). Minor/Significance Unknown. Comment: Decreased symptoms of hypoglycemia. Mechanism: decreased hypoglycemia induced catecholamine production.

                guanfacine decreases effects of insulin NPH by pharmacodynamic antagonism. Minor/Significance Unknown. Diminished symptoms of hypoglycemia.

              • insulin regular human

                guanfacine decreases effects of insulin regular human by pharmacodynamic antagonism. Minor/Significance Unknown. Diminished symptoms of hypoglycemia.

                guanfacine, insulin regular human. Other (see comment). Minor/Significance Unknown. Comment: Decreased symptoms of hypoglycemia. Mechanism: decreased hypoglycemia induced catecholamine production.

              • maitake

                maitake increases effects of guanfacine by pharmacodynamic synergism. Minor/Significance Unknown.

              • metformin

                guanfacine decreases effects of metformin by pharmacodynamic antagonism. Minor/Significance Unknown. Diminished symptoms of hypoglycemia.

                guanfacine, metformin. Other (see comment). Minor/Significance Unknown. Comment: Decreased symptoms of hypoglycemia. Mechanism: decreased hypoglycemia induced catecholamine production.

              • metoprolol

                metoprolol, guanfacine. Mechanism: pharmacodynamic synergism. Minor/Significance Unknown. Selective beta blocker administration during withdrawal from centrally acting alpha agonists may result in rebound hypertension.

              • miglitol

                guanfacine decreases effects of miglitol by pharmacodynamic antagonism. Minor/Significance Unknown. Diminished symptoms of hypoglycemia.

                guanfacine, miglitol. Other (see comment). Minor/Significance Unknown. Comment: Decreased symptoms of hypoglycemia. Mechanism: decreased hypoglycemia induced catecholamine production.

              • nateglinide

                guanfacine decreases effects of nateglinide by pharmacodynamic antagonism. Minor/Significance Unknown. Diminished symptoms of hypoglycemia.

                guanfacine, nateglinide. Other (see comment). Minor/Significance Unknown. Comment: Decreased symptoms of hypoglycemia. Mechanism: decreased hypoglycemia induced catecholamine production.

              • nebivolol

                nebivolol, guanfacine. Mechanism: pharmacodynamic synergism. Minor/Significance Unknown. Selective beta blocker administration during withdrawal from centrally acting alpha agonists may result in rebound hypertension.

              • octacosanol

                octacosanol increases effects of guanfacine by pharmacodynamic synergism. Minor/Significance Unknown.

              • penbutolol

                penbutolol, guanfacine. Mechanism: pharmacodynamic synergism. Minor/Significance Unknown. Selective beta blocker administration during withdrawal from centrally acting alpha agonists may result in rebound hypertension.

              • pioglitazone

                guanfacine decreases effects of pioglitazone by pharmacodynamic antagonism. Minor/Significance Unknown. Diminished symptoms of hypoglycemia.

                guanfacine, pioglitazone. Other (see comment). Minor/Significance Unknown. Comment: Decreased symptoms of hypoglycemia. Mechanism: decreased hypoglycemia induced catecholamine production.

              • reishi

                reishi increases effects of guanfacine by pharmacodynamic synergism. Minor/Significance Unknown.

              • repaglinide

                guanfacine decreases effects of repaglinide by pharmacodynamic antagonism. Minor/Significance Unknown. Diminished symptoms of hypoglycemia.

                guanfacine, repaglinide. Other (see comment). Minor/Significance Unknown. Comment: Decreased symptoms of hypoglycemia. Mechanism: decreased hypoglycemia induced catecholamine production.

              • rosiglitazone

                guanfacine decreases effects of rosiglitazone by pharmacodynamic antagonism. Minor/Significance Unknown. Diminished symptoms of hypoglycemia.

                guanfacine, rosiglitazone. Other (see comment). Minor/Significance Unknown. Comment: Decreased symptoms of hypoglycemia. Mechanism: decreased hypoglycemia induced catecholamine production.

              • saxagliptin

                guanfacine decreases effects of saxagliptin by pharmacodynamic antagonism. Minor/Significance Unknown. Diminished symptoms of hypoglycemia.

                guanfacine, saxagliptin. Other (see comment). Minor/Significance Unknown. Comment: Decreased symptoms of hypoglycemia. Mechanism: decreased hypoglycemia induced catecholamine production.

              • shepherd's purse

                shepherd's purse, guanfacine. Other (see comment). Minor/Significance Unknown. Comment: Theoretically, shepherd's purse may interfere with BP control.

              • sitagliptin

                guanfacine decreases effects of sitagliptin by pharmacodynamic antagonism. Minor/Significance Unknown. Diminished symptoms of hypoglycemia.

                guanfacine, sitagliptin. Other (see comment). Minor/Significance Unknown. Comment: Decreased symptoms of hypoglycemia. Mechanism: decreased hypoglycemia induced catecholamine production.

              • sotalol

                sotalol, guanfacine. Mechanism: pharmacodynamic synergism. Minor/Significance Unknown. Selective beta blocker administration during withdrawal from centrally acting alpha agonists may result in rebound hypertension.

              • tizanidine

                tizanidine increases effects of guanfacine by pharmacodynamic synergism. Minor/Significance Unknown. Risk of hypotension.

              • tolazamide

                guanfacine decreases effects of tolazamide by pharmacodynamic antagonism. Minor/Significance Unknown. Diminished symptoms of hypoglycemia.

                guanfacine, tolazamide. Other (see comment). Minor/Significance Unknown. Comment: Decreased symptoms of hypoglycemia. Mechanism: decreased hypoglycemia induced catecholamine production.

              • tolbutamide

                guanfacine decreases effects of tolbutamide by pharmacodynamic antagonism. Minor/Significance Unknown. Diminished symptoms of hypoglycemia.

                guanfacine, tolbutamide. Other (see comment). Minor/Significance Unknown. Comment: Decreased symptoms of hypoglycemia. Mechanism: decreased hypoglycemia induced catecholamine production.

              • treprostinil

                treprostinil increases effects of guanfacine by pharmacodynamic synergism. Minor/Significance Unknown.

              • vildagliptin

                guanfacine decreases effects of vildagliptin by pharmacodynamic antagonism. Minor/Significance Unknown. Diminished symptoms of hypoglycemia.

                guanfacine, vildagliptin. Other (see comment). Minor/Significance Unknown. Comment: Decreased symptoms of hypoglycemia. Mechanism: decreased hypoglycemia induced catecholamine production.

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              Adverse Effects

              >10%

              Xerostomia (10-60%)

              Somnolence (5-39%)

              Headache (0.2-26%)

              Dizziness (2-15%)

              Constipation (2-16%)

              Fatigue (2-15%)

              Abdominal pain (11%)

              Extended-release tablets

              • Somnolence (6-38%)
              • Headache (23%)
              • Dizziness (6-16%)
              • Decreased appetite (6-15%)
              • Fatigue (2-14%)
              • Abdominal pain (11%)

              1-10%

              Hypotension (7%)

              Asthenia (2-7%)

              Impotence (0-7%)

              Lethargy (6%)

              Dizziness (6%)

              Irritability (6%)

              Nausea (3-6%)

              Decreased appetite (5%)

              Weakness (1-5%)

              Insomnia (3-4%)

              Bradycardia (3%)

              Palpitations (3%)

              Confusion (3%)

              Depression (3%)

              Dyspnea (3%)

              Alopecia (3%)

              Dermatitis (3%)

              Diaphoresis (3%)

              Pruritus (3%)

              Dyspepsia (3%)

              Dysphagia (3%)

              Hypokinesia (3%)

              Leg cramps (3%)

              Extended-release tablets

              • Hypotension (7%)
              • Insomnia (7%)
              • Irritability (6%)
              • Lethargy (6%)
              • Nausea (6%)
              • Postural dizziness (5%)
              • Bradycardia (5%)
              • Diarrhea (5%)
              • Anxiety (5%)
              • Dry mouth (3-4%)
              • Constipation (3%)
              • Increased weight (3%)
              • Rash (3%)
              • Nightmare (2%)
              • Enuresis (2%)

              Frequency Not Defined

              Orthostatic hypotension

              Exfoliation

              Rash

              Arthralgia

              Myalgia

              Extended-release tablets

              • Atrioventricular block
              • Asthenia
              • Chest pain
              • Hypersensitivity
              • Increased alanine aminotransferase
              • Convulsion Increased urinary frequency
              • Hypertension
              • Pallor

              Postmarketing Reports

              Cardiovascular: Bradycardia, palpitations, syncope, tachycardia, rebound hypertension, hypertensive encephalopathy

              CNS: Paresthesias, vertigo

              GI: Abdominal pain, constipation, diarrhea, dyspepsia

              Liver/biliary: Abnormal LFTs

              Musculoskeletal: Arthralgia, leg cramps, leg pain, myalgia

              Psychiatric: Agitation, anxiety, confusion, depression, hallucinations, insomnia, nervousness

              Reproductive: Impotence

              Respiratory: Dyspnea

              Skin: Alopecia, dermatitis, exfoliative dermatitis, pruritus, rash

              Sensory: Blurred vision, alterations in taste

              Urinary: Nocturia, urinary frequency

              Other: Asthenia, chest pain, edema, malaise, tremor

              Extended-release tablets

              • General: Edema, malaise, tremor
              • Cardiovascular: Palpitations, tachycardia, rebound hypertension, hypertensive encephalopathy
              • Central nervous system: Paresthesias, vertigo
              • Eye disorders: blurred vision
              • Musculoskeletal System: Arthralgia, leg cramps, leg pain, myalgia
              • Psychiatric: Confusion, hallucinations
              • Reproductive system, male: Erectile dysfunction
              • Respiratory System: Dyspnea
              • Skin and appendages: Alopecia, dermatitis, exfoliative dermatitis, pruritus, rash
              • Special senses: Alterations in taste
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              Warnings

              Contraindications

              Hypersensitivity

              Cautions

              Avoid abrupt withdrawal (can result in anxiety, nervousness, and rebound hypertension)

              May cause hypotension, orthostasis, bradycardia, and syncope, use with caution in history of cerebrovascular disease, recent MI, severe coronary insufficiency, or syncope

              Chronic renal/hepatic failure

              May cause sedation, especially at start; avoid operating heavy machinery

              Skin rash with exfoliation reported

              Avoid concomitant use with other CNS depressants (eg, alcohol) as they may potentiate CNS effects

              Risk of cardiovascular effects may increase when administered concurrently with antihypertensive medications or drugs that affect heart rate

              In post marketing experience, abrupt discontinuation of the extended-release tablets has resulted in clinically significant and persistent rebound hypertension above baseline levels and increases in heart rate; hypertensive encephalopathy reported in association with rebound hypertension with guanfacine

              ADHD

              • Hypotension is dose-limiting
              • Do not substitute extended-release tablet for immediate-release guanfacine on a mg/mg basis, because of differing pharmacokinetic profiles
              • May cause dose-dependent hypotension, bradycardia, and syncope
              • Hallucinations reported in children with ADHD treated with guanfacine

              Geriatric patients

              • May cause adverse CNS effects
              • May cause bradycardia and orthostatic hypotension
              • Not recommended as routine treatment for hypertension (Beers criteria)
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              Pregnancy & Lactation

              Pregnancy

              There is pregnancy exposure registry that monitors pregnancy outcomes in women exposed to ADHD medications, during pregnancy; healthcare providers are encouraged to register patients by calling National Pregnancy Registry for ADHD Medications at 1-866-961-2388.

              Available data with guanfacine over decades of use in pregnant women have not identified a drug-associated risk of major birth defects, miscarriage or adverse maternal or fetal outcomes; however, use of guanfacine in pregnant women over this time has been infrequent;

              Animal data

              • In animal reproduction studies, rabbits and rats exposed to 3 and 4 times the maximum recommended human dose (MRHD), respectively, showed no adverse outcomes. However, higher doses were associated with reduced fetal survival and maternal toxicity

              Lactation

              There are no data on presence of guanfacine in human milk or effects on breastfed infant; effects on milk production are also unknown; drug is present in milk of lactating rats; if drug is present in animal milk, it is likely that drug will be present in human milk; if an infant is exposed to drug through breastmilk, monitor for symptoms of hypotension and bradycardia such as sedation, lethargy and poor feeding; the developmental and health benefits of breastfeeding should be considered along with mother’s clinical need for drug and any potential adverse effects on breastfed child from therapy or from underlying maternal condition.

              Monitor breastfeeding infants exposed to guanfacine through breastmilk for sedation, lethargy, and poor feeding

              Pregnancy Categories

              A: Generally acceptable. Controlled studies in pregnant women show no evidence of fetal risk.

              B: May be acceptable. Either animal studies show no risk but human studies not available or animal studies showed minor risks and human studies done and showed no risk.

              C: Use with caution if benefits outweigh risks. Animal studies show risk and human studies not available or neither animal nor human studies done.

              D: Use in LIFE-THREATENING emergencies when no safer drug available. Positive evidence of human fetal risk.

              X: Do not use in pregnancy. Risks involved outweigh potential benefits. Safer alternatives exist.

              NA: Information not available.

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              Pharmacology

              Mechanism of Action

              Selective alpha2-adrenergic receptor agonist causing decreased sympathetic outflow and subsequent decrease in vasomotor tone and heart rate; may preferentially bind postsynaptic alpha2A adrenoreceptors in the prefrontal cortex, which may improve delay-related firing of prefrontal cortex neurons (as a result, behavioral inhibition may be affected); mechanism of action in ADHD is not known

              Absorption

              AUC: 56 ng·hr/mL (immediate release tablets); 32 ng·hr/mL (extended release tablets)

              Peak plasma concentration: 2.5 ng/mL (Immediate release tablets); 1 ng/mL (extended release tablets)

              Peak plasma time: 3 hr (immediate release tablets); 6 hr (extended release tablets)

              Bioavailability: 80-100% (immediate release tablets); 58% (extended release tablets)

              Onset: Initial effect (2 hr); maximum effect (6 hr)

              Duration: 24 hr

              Distribution

              Protein bound: 70%

              Vd: 6.3 L/kg

              Metabolism

              Via CYP3A4 (hepatic)

              Metabolites: Glucuronide and sulfate of 3-hydroxy guanfacine, oxidized mercapturic acid derivatives (inactive)

              Elimination

              Half-life: 16 hr (immediate release tablets); 18 hr (extended release tablets)

              Dialyzable: HD (No)

              Excretion: Urine 80% (unchanged)

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              Administration

              Oral Administration

              Administer orally once a day

              Extended-release tablets

              • Do not administer with high-fat meals due to potential for increased serum levels
              • Swallow tablets whole; do not crush, chew, or break tablets because this will increase the rate of guanfacine release
              • Missed dose: Repeat dosage titration based on patient tolerability

              Storage

              Immediate-release tablets: at 20-25°C (68-77°F); dispense in a tight, light-resistant container

              Extended-release tablets: Store at 20-25°C (68-77°F); excursions permitted to 15-30°C (59-86°F)

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              Images

              BRAND FORM. UNIT PRICE PILL IMAGE
              Intuniv ER oral
              -
              1 mg tablet
              Intuniv ER oral
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              2 mg tablet
              Intuniv ER oral
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              4 mg tablet
              Intuniv ER oral
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              3 mg tablet
              guanfacine oral
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              4 mg tablet
              guanfacine oral
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              3 mg tablet
              guanfacine oral
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              2 mg tablet
              guanfacine oral
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              1 mg tablet
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              guanfacine oral
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              1 mg tablet
              guanfacine oral
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              guanfacine oral
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              guanfacine oral
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              1 mg tablet
              guanfacine oral
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              4 mg tablet
              guanfacine oral
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              guanfacine oral
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              guanfacine oral
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              guanfacine oral
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              guanfacine oral
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              guanfacine oral
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              guanfacine oral
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              1 mg tablet
              guanfacine oral
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              1 mg tablet
              guanfacine oral
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              1 mg tablet
              guanfacine oral
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              4 mg tablet
              guanfacine oral
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              1 mg tablet
              guanfacine oral
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              guanfacine oral
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              guanfacine oral
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              guanfacine oral
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              guanfacine oral
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              2 mg tablet
              guanfacine oral
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              2 mg tablet
              guanfacine oral
              -
              1 mg tablet
              guanfacine oral
              -
              2 mg tablet

              Copyright © 2010 First DataBank, Inc.

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              Patient Handout

              Patient Education
              guanfacine oral

              GUANFACINE - ORAL

              (GWAN-fuh-seen)

              COMMON BRAND NAME(S): Tenex

              USES: This medication is used alone or with other medications to treat high blood pressure (hypertension). Lowering high blood pressure helps prevent strokes, heart attacks, and kidney problems. Guanfacine acts in the brain. It decreases certain nerve signals from the brain to the blood vessels and the heart. This causes the blood vessels to relax so that blood can flow more easily and also slows the heart rate. These effects help to lower blood pressure.

              HOW TO USE: Take this medication by mouth with or without food, usually once daily at bedtime or as directed by your doctor.The dosage is based on your medical condition, response to treatment, and other medications you may be taking. Be sure to tell your doctor and pharmacist about all the products you use (including prescription drugs, nonprescription drugs, and herbal products).Use this medication regularly to get the most benefit from it. To help you remember, take it at the same time each day.It may take several weeks before you get the full benefit of this medication. Keep taking this medication even if you feel well. Most people with high blood pressure do not feel sick.Do not stop taking this medication without consulting your doctor. Some conditions may become worse when this drug is suddenly stopped. Also, you may experience symptoms such as headache, nervousness, agitation, tremor, fast heartbeat, and high blood pressure. To prevent these symptoms while you are stopping treatment with this drug, your doctor may reduce your dose gradually. Ask your doctor or pharmacist for more details. Report any new or worsening symptoms right away.Tell your doctor if your condition does not improve or if it worsens (for example, your routine blood pressure readings remain high or increase).

              SIDE EFFECTS: Dry mouth, drowsiness, dizziness, constipation, tiredness, and weakness may occur. Decreased sexual ability has been reported rarely. If any of these effects persist or worsen, tell your doctor or pharmacist promptly.To relieve dry mouth, suck on (sugarless) hard candy or ice chips, chew (sugarless) gum, drink water, or use a saliva substitute.To lower your risk of dizziness and lightheadedness, get up slowly when rising from a sitting or lying position.Remember that this medication has been prescribed because your doctor has judged that the benefit to you is greater than the risk of side effects. Many people using this medication do not have serious side effects.Tell your doctor right away if you have any serious side effects, including: severe dizziness, fast/slow heartbeat, fainting, mental/mood changes (such as depression, hallucinations, confusion, thoughts of suicide).A very serious allergic reaction to this drug is rare. However, seek immediate medical attention if you notice any symptoms of a serious allergic reaction, including: rash, itching/swelling (especially of the face/tongue/throat), severe dizziness, trouble breathing.This is not a complete list of possible side effects. If you notice other effects not listed above, contact your doctor or pharmacist.In the US -Call your doctor for medical advice about side effects. You may report side effects to FDA at 1-800-FDA-1088 or at www.fda.gov/medwatch.In Canada - Call your doctor for medical advice about side effects. You may report side effects to Health Canada at 1-866-234-2345.

              PRECAUTIONS: Before taking guanfacine, tell your doctor or pharmacist if you are allergic to it; or if you have any other allergies. This product may contain inactive ingredients, which can cause allergic reactions or other problems. Talk to your pharmacist for more details.Before using this medication, tell your doctor or pharmacist your medical history, especially of: kidney disease, liver disease, personal/family history of mental/mood disorders (such as bipolar disorder, depression, suicidal thoughts).This drug may make you dizzy or drowsy. Alcohol or marijuana (cannabis) can make you more dizzy or drowsy. Do not drive, use machinery, or do anything that needs alertness until you can do it safely. Limit alcoholic beverages. Talk to your doctor if you are using marijuana (cannabis).Before having surgery, tell your doctor or dentist that you are taking this medication.Children may be more sensitive to the side effects of this drug, especially hallucinations and mental/mood changes.Older adults may be more sensitive to the side effects of this drug, especially dizziness (more likely when standing up), drowsiness, slow heartbeat, or depression. Dizziness and drowsiness can increase the risk of falling.During pregnancy, this medication should be used only when clearly needed. Discuss the risks and benefits with your doctor.It is unknown if this medication passes into breast milk. Consult your doctor before breast-feeding.

              DRUG INTERACTIONS: Drug interactions may change how your medications work or increase your risk for serious side effects. This document does not contain all possible drug interactions. Keep a list of all the products you use (including prescription/nonprescription drugs and herbal products) and share it with your doctor and pharmacist. Do not start, stop, or change the dosage of any medicines without your doctor's approval.Tell your doctor or pharmacist if you are taking other products that cause drowsiness including alcohol, marijuana (cannabis), antihistamines (such as cetirizine, diphenhydramine), drugs for sleep or anxiety (such as alprazolam, diazepam, zolpidem), muscle relaxants (such as carisoprodol, cyclobenzaprine), and opioid pain relievers (such as codeine, hydrocodone).Check the labels on all your medicines (such as cough-and-cold products, diet aids, nonsteroidal anti-inflammatory drugs-NSAIDs such as ibuprofen for pain/fever reduction) because they may contain ingredients that cause drowsiness or could increase your blood pressure or heart rate. Ask your pharmacist about using those products safely.

              OVERDOSE: If someone has overdosed and has serious symptoms such as passing out or trouble breathing, call 911. Otherwise, call a poison control center right away. US residents can call their local poison control center at 1-800-222-1222. Canada residents can call a provincial poison control center. Symptoms of overdose may include: severe drowsiness, severe dizziness, severe tiredness, very slow heartbeat.

              NOTES: Do not share this medication with others.Talk with your doctor about making changes to your lifestyle that may help this medication work better (such as stress reduction programs, exercise, and dietary changes).Have your blood pressure and heart rate checked regularly while taking this medication. Learn how to check your own blood pressure and heart rate at home, and share the results with your doctor.

              MISSED DOSE: If you miss a dose, take it as soon as you remember. If it is near the time of the next dose, skip the missed dose. Take your next dose at the regular time. Do not double the dose to catch up.

              STORAGE: Store at room temperature away from light and moisture. Do not store in the bathroom. Keep all medications away from children and pets.Do not flush medications down the toilet or pour them into a drain unless instructed to do so. Properly discard this product when it is expired or no longer needed. Consult your pharmacist or local waste disposal company.

              Information last revised August 2021. Copyright(c) 2021 First Databank, Inc.

              IMPORTANT: HOW TO USE THIS INFORMATION: This is a summary and does NOT have all possible information about this product. This information does not assure that this product is safe, effective, or appropriate for you. This information is not individual medical advice and does not substitute for the advice of your health care professional. Always ask your health care professional for complete information about this product and your specific health needs.

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              Formulary

              FormularyPatient Discounts

              Adding plans allows you to compare formulary status to other drugs in the same class.

              To view formulary information first create a list of plans. Your list will be saved and can be edited at any time.

              Adding plans allows you to:

              • View the formulary and any restrictions for each plan.
              • Manage and view all your plans together – even plans in different states.
              • Compare formulary status to other drugs in the same class.
              • Access your plan list on any device – mobile or desktop.

              The above information is provided for general informational and educational purposes only. Individual plans may vary and formulary information changes. Contact the applicable plan provider for the most current information.

              Tier Description
              1 This drug is available at the lowest co-pay. Most commonly, these are generic drugs.
              2 This drug is available at a middle level co-pay. Most commonly, these are "preferred" (on formulary) brand drugs.
              3 This drug is available at a higher level co-pay. Most commonly, these are "non-preferred" brand drugs.
              4 This drug is available at a higher level co-pay. Most commonly, these are "non-preferred" brand drugs or specialty prescription products.
              5 This drug is available at a higher level co-pay. Most commonly, these are "non-preferred" brand drugs or specialty prescription products.
              6 This drug is available at a higher level co-pay. Most commonly, these are "non-preferred" brand drugs or specialty prescription products.
              NC NOT COVERED – Drugs that are not covered by the plan.
              Code Definition
              PA Prior Authorization
              Drugs that require prior authorization. This restriction requires that specific clinical criteria be met prior to the approval of the prescription.
              QL Quantity Limits
              Drugs that have quantity limits associated with each prescription. This restriction typically limits the quantity of the drug that will be covered.
              ST Step Therapy
              Drugs that have step therapy associated with each prescription. This restriction typically requires that certain criteria be met prior to approval for the prescription.
              OR Other Restrictions
              Drugs that have restrictions other than prior authorization, quantity limits, and step therapy associated with each prescription.
              Additional Offers
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              Medscape prescription drug monographs are based on FDA-approved labeling information, unless otherwise noted, combined with additional data derived from primary medical literature.