dextromethorphan (OTC)

Brand and Other Names:Balminil DM, Benylin DM, more...Bronchophan, Buckleys DM, Calmylin #1, Delsym, Koffex DM, Novahistex DM, Robitussin Lingering Cold Long-Acting Cough, Robitussin Lingering Cold Long-Acting CoughGels, Children's Robitussin Cough Long-Acting, Sucrets 8 Hour Cough Relief DM Cough Formula
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Dosing & Uses

AdultPediatric

Dosage Forms & Strengths

tablet

  • 15mg

capsule

  • 15mg

gel, oral

  • 7.5mg/5mL

liquid, oral

  • 7.5mg/5mL
  • 10mg/5mL
  • 15mg/5mL

syrup, oral

  • 5mg/5mL
  • 7.5mg/5mL
  • 10mg/5mL
  • 15mg/5mL
  • 20mg/15mL

liquid, extended release

  • 30mg/5mL

lozenge

  • 5mg
  • 7.5mg
  • 15mg

strip, oral

  • 7.5mg

Cough

Liquid and syrup: 10-20 mg PO q4hr OR 30 mg q6-8hr

Gel: 30 mg PO q6-8hr; not to exceed 120 mg/24hr

Extended release: 60 mg PO q12hr; not to exceed 120 mg/24hr

Lozenges: 5-15 mg PO q1-4hr; not to exceed 120 mg/day

Strips: 30 mg PO q6-8hr; not to exceed 120 mg/day

Dosing considerations

  • Abuse potential much lower than codeine
  • About 15-30 mg dextromethorphan equal to 8-15 mg codeine as an antitussive

Dosage Forms & Strengths

tablet

  • 15mg

capsule

  • 15mg
  • 25mg

gel, oral

  • 7.5mg/5mL

syrup

  • 5mg/5mL
  • 7.5mg/5mL
  • 10mg/5mL
  • 15mg/5mL
  • 20mg/15mL

liquid, extended release

  • 30mg/5mL

lozenge

  • 5mg
  • 7.5mg
  • 15mg

strip, oral

  • 7.5mg

Cough

<4 years

  • Prescription only

Extended release

  • 4-6 years: 15 mg PO twice daily; not to exceed 30 mg/24hr
  • 6-12 years: 30 mg PO twice daily; not to exceed 60 mg/24hr
  • >12 years: 60 mg PO q12hr; not to exceed 120 mg/24hr

Liquid/Syrup

  • 4-6 years: 7.5 mg q6-8hr (not to exceed 30 mg/day)
  • 6-12 years: 15 mg PO q6-8hr; not to exceed 60 mg/24hr
  • 12 years: 10-20 mg PO q4hr or 30 mg q6-8hr not to exceed 120 mg/24hr

Gel

  • >12 years: 30 mg PO q6-8hr; not to exceed 120 mg/24hr

Lozenges

  • 6-12 years: 5-10 mg q1-4hr; not to exceed 60 mg/day
  • >12 years: 5-15 mg PO q1-4hr; not to exceed 120 mg/day

Strips

  • 6-12 years: 15 mg PO q6-8hr; not to exceed 60 mg/day
  • >12 years: 30 mg PO q6-8hr; not to exceed 120 mg/day

Dosing considerations

  • Potential toxic dose <6 years: 10 mg/kg  
  • About 15-30 mg dextromethorphan equal to 8-15 mg codeine as an antitussive
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Interactions

Interaction Checker

and dextromethorphan

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      Serious - Use Alternative

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            Contraindicated (7)

            • isocarboxazid

              isocarboxazid and dextromethorphan both increase serotonin levels. Contraindicated.

            • phenelzine

              phenelzine and dextromethorphan both increase serotonin levels. Contraindicated.

            • procarbazine

              procarbazine and dextromethorphan both increase serotonin levels. Contraindicated. Combination is contraindicated within 2 weeks of MAOI use.

            • rasagiline

              rasagiline and dextromethorphan both increase serotonin levels. Contraindicated. Risk of psychosis episodes or bizarre behavior.

            • safinamide

              dextromethorphan, safinamide. Other (see comment). Contraindicated. Comment: Coadministration of MAOIs and dextromethorphan has been reported to cause episodes of psychosis or bizarre behavior.

            • selegiline

              selegiline and dextromethorphan both increase serotonin levels. Contraindicated.

            • tranylcypromine

              tranylcypromine and dextromethorphan both increase serotonin levels. Contraindicated.

            Serious - Use Alternative (34)

            • amitriptyline

              amitriptyline and dextromethorphan both increase serotonin levels. Avoid or Use Alternate Drug.

            • amoxapine

              amoxapine and dextromethorphan both increase serotonin levels. Avoid or Use Alternate Drug.

            • buspirone

              buspirone and dextromethorphan both increase serotonin levels. Avoid or Use Alternate Drug.

            • citalopram

              citalopram and dextromethorphan both increase serotonin levels. Avoid or Use Alternate Drug. Combination may increase risk of serotonin syndrome or neuroleptic malignant syndrome-like reactions.

            • clomipramine

              clomipramine and dextromethorphan both increase serotonin levels. Avoid or Use Alternate Drug.

            • desipramine

              desipramine and dextromethorphan both increase serotonin levels. Avoid or Use Alternate Drug.

            • desvenlafaxine

              dextromethorphan and desvenlafaxine both increase serotonin levels. Avoid or Use Alternate Drug.

            • doxepin

              doxepin and dextromethorphan both increase serotonin levels. Avoid or Use Alternate Drug.

            • duloxetine

              duloxetine will increase the level or effect of dextromethorphan by affecting hepatic enzyme CYP2D6 metabolism. Avoid or Use Alternate Drug.

              duloxetine and dextromethorphan both increase serotonin levels. Avoid or Use Alternate Drug.

            • escitalopram

              escitalopram and dextromethorphan both increase serotonin levels. Avoid or Use Alternate Drug.

            • fluoxetine

              fluoxetine will increase the level or effect of dextromethorphan by affecting hepatic enzyme CYP2D6 metabolism. Avoid or Use Alternate Drug.

              fluoxetine and dextromethorphan both increase serotonin levels. Avoid or Use Alternate Drug.

            • fluvoxamine

              fluvoxamine and dextromethorphan both increase serotonin levels. Avoid or Use Alternate Drug.

            • grapefruit

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

            • imipramine

              imipramine and dextromethorphan both increase serotonin levels. Avoid or Use Alternate Drug.

            • levomilnacipran

              levomilnacipran and dextromethorphan both increase serotonin levels. Avoid or Use Alternate Drug.

            • linezolid

              linezolid and dextromethorphan both increase serotonin levels. Avoid or Use Alternate Drug. Linezolid may increase serotonin as a result of MAO-A inhibition. If linezolid must be administered, discontinue serotonergic drug immediately and monitor for CNS toxicity. Serotonergic therapy may be resumed 24 hours after last linezolid dose or after 2 weeks of monitoring, whichever comes first.

            • lofepramine

              lofepramine and dextromethorphan both increase serotonin levels. Avoid or Use Alternate Drug.

            • lorcaserin

              dextromethorphan and lorcaserin both increase serotonin levels. Avoid or Use Alternate Drug.

            • maprotiline

              maprotiline and dextromethorphan both increase serotonin levels. Avoid or Use Alternate Drug.

            • memantine

              memantine, dextromethorphan. Either increases toxicity of the other by pharmacodynamic synergism. Contraindicated.

            • meperidine

              dextromethorphan and meperidine both increase serotonin levels. Avoid or Use Alternate Drug.

            • methylene blue

              methylene blue and dextromethorphan both increase serotonin levels. Avoid or Use Alternate Drug. Methylene blue may increase serotonin as a result of MAO-A inhibition. If methylene blue must be administered, discontinue serotonergic drug immediately and monitor for CNS toxicity. Serotonergic therapy may be resumed 24 hours after last methylene blue dose or after 2 weeks of monitoring, whichever comes first.

            • milnacipran

              milnacipran and dextromethorphan both increase serotonin levels. Avoid or Use Alternate Drug.

            • nefazodone

              nefazodone and dextromethorphan both increase serotonin levels. Avoid or Use Alternate Drug.

            • nortriptyline

              nortriptyline and dextromethorphan both increase serotonin levels. Avoid or Use Alternate Drug.

            • paroxetine

              paroxetine will increase the level or effect of dextromethorphan by affecting hepatic enzyme CYP2D6 metabolism. Avoid or Use Alternate Drug.

              paroxetine and dextromethorphan both increase serotonin levels. Avoid or Use Alternate Drug.

            • protriptyline

              protriptyline and dextromethorphan both increase serotonin levels. Avoid or Use Alternate Drug.

            • selegiline transdermal

              selegiline transdermal and dextromethorphan both increase serotonin levels. Avoid or Use Alternate Drug.

            • sertraline

              sertraline and dextromethorphan both increase serotonin levels. Avoid or Use Alternate Drug.

            • St John's Wort

              dextromethorphan and St John's Wort both increase serotonin levels. Avoid or Use Alternate Drug.

            • trazodone

              trazodone and dextromethorphan both increase serotonin levels. Avoid or Use Alternate Drug.

            • trimipramine

              trimipramine and dextromethorphan both increase serotonin levels. Avoid or Use Alternate Drug.

            • venlafaxine

              venlafaxine will increase the level or effect of dextromethorphan by affecting hepatic enzyme CYP2D6 metabolism. Avoid or Use Alternate Drug.

              venlafaxine and dextromethorphan both increase serotonin levels. Avoid or Use Alternate Drug.

            • vilazodone

              dextromethorphan, vilazodone. Either increases toxicity of the other by serotonin levels. Avoid or Use Alternate Drug. Concomitant therapy should be discontinued immediately if signs or symptoms of serotonin syndrome emerge and supportive symptomatic treatment should be initiated. .

            Monitor Closely (58)

            • 5-HTP

              5-HTP and dextromethorphan both increase serotonin levels. Modify Therapy/Monitor Closely.

            • abiraterone

              abiraterone increases levels of dextromethorphan by affecting hepatic enzyme CYP2D6 metabolism. Use Caution/Monitor. Avoid coadministration of abiraterone with substrates of CYP2D6. If alternative therapy cannot be used, exercise caution and consider a dose reduction of the CYP2D6 substrate.

            • almotriptan

              almotriptan and dextromethorphan both increase serotonin levels. Modify Therapy/Monitor Closely.

            • aripiprazole

              dextromethorphan, aripiprazole. unspecified interaction mechanism. Use Caution/Monitor. Serotonin modulators may enhance dopamine blockade, possibly increasing the risk for neuroleptic malignant syndrome. Antipsychotics may enhance serotonergic effect of serotonin modulators, which may result in serotonin syndrome. Monitor for evidence of serotonin toxicity (eg, mental status changes, autonomic instability, and neuromuscular hyperactivity) or neuroleptic malignant syndrome (eg, hyperthermia, muscle rigidity, autonomic dysfunction).

            • artemether/lumefantrine

              artemether/lumefantrine will increase the level or effect of dextromethorphan by affecting hepatic enzyme CYP2D6 metabolism. Use Caution/Monitor.

            • asenapine

              dextromethorphan, asenapine. unspecified interaction mechanism. Use Caution/Monitor. Serotonin modulators may enhance dopamine blockade, possibly increasing the risk for neuroleptic malignant syndrome. Antipsychotics may enhance serotonergic effect of serotonin modulators, which may result in serotonin syndrome. Monitor for evidence of serotonin toxicity (eg, mental status changes, autonomic instability, and neuromuscular hyperactivity) or neuroleptic malignant syndrome (eg, hyperthermia, muscle rigidity, autonomic dysfunction).

            • bupropion

              bupropion will increase the level or effect of dextromethorphan by affecting hepatic enzyme CYP2D6 metabolism. Use Caution/Monitor.

            • cariprazine

              dextromethorphan, cariprazine. unspecified interaction mechanism. Use Caution/Monitor. Serotonin modulators may enhance dopamine blockade, possibly increasing the risk for neuroleptic malignant syndrome. Antipsychotics may enhance serotonergic effect of serotonin modulators, which may result in serotonin syndrome. Monitor for evidence of serotonin toxicity (eg, mental status changes, autonomic instability, and neuromuscular hyperactivity) or neuroleptic malignant syndrome (eg, hyperthermia, muscle rigidity, autonomic dysfunction).

            • clobazam

              clobazam will increase the level or effect of dextromethorphan by affecting hepatic enzyme CYP2D6 metabolism. Use Caution/Monitor. Lower doses of drugs metabolized by CYP2D6 may be required when used concomitantly.

            • clozapine

              dextromethorphan, clozapine. unspecified interaction mechanism. Use Caution/Monitor. Serotonin modulators may enhance dopamine blockade, possibly increasing the risk for neuroleptic malignant syndrome. Antipsychotics may enhance serotonergic effect of serotonin modulators, which may result in serotonin syndrome. Monitor for evidence of serotonin toxicity (eg, mental status changes, autonomic instability, and neuromuscular hyperactivity) or neuroleptic malignant syndrome (eg, hyperthermia, muscle rigidity, autonomic dysfunction).

            • cocaine

              cocaine and dextromethorphan both increase serotonin levels. Modify Therapy/Monitor Closely.

            • desvenlafaxine

              desvenlafaxine will increase the level or effect of dextromethorphan by affecting hepatic enzyme CYP2D6 metabolism. Use Caution/Monitor. Desvenlafaxine inhibits CYP2D6; with higher desvenlafaxine doses (ie, 400 mg) decrease the CYP2D6 substrate dose by up to 50%; no dosage adjustment needed with desvenlafaxine doses <100 mg

            • dexfenfluramine

              dexfenfluramine and dextromethorphan both increase serotonin levels. Modify Therapy/Monitor Closely.

            • dextroamphetamine

              dextroamphetamine and dextromethorphan both increase serotonin levels. Modify Therapy/Monitor Closely.

            • dihydroergotamine

              dextromethorphan and dihydroergotamine both increase serotonin levels. Modify Therapy/Monitor Closely.

            • dihydroergotamine intranasal

              dextromethorphan and dihydroergotamine intranasal both increase serotonin levels. Modify Therapy/Monitor Closely.

            • eletriptan

              eletriptan and dextromethorphan both increase serotonin levels. Modify Therapy/Monitor Closely.

            • ergotamine

              dextromethorphan and ergotamine both increase serotonin levels. Modify Therapy/Monitor Closely.

            • fenfluramine

              dextromethorphan and fenfluramine both increase serotonin levels. Modify Therapy/Monitor Closely.

              fenfluramine, dextromethorphan. Either increases effects of the other by serotonin levels. Use Caution/Monitor. Coadministration with drugs that increase serotoninergic effects may increase the risk of serotonin syndrome.

            • fluphenazine

              dextromethorphan, fluphenazine. unspecified interaction mechanism. Use Caution/Monitor. Serotonin modulators may enhance dopamine blockade, possibly increasing the risk for neuroleptic malignant syndrome. Antipsychotics may enhance serotonergic effect of serotonin modulators, which may result in serotonin syndrome. Monitor for evidence of serotonin toxicity (eg, mental status changes, autonomic instability, and neuromuscular hyperactivity) or neuroleptic malignant syndrome (eg, hyperthermia, muscle rigidity, autonomic dysfunction).

            • frovatriptan

              frovatriptan and dextromethorphan both increase serotonin levels. Modify Therapy/Monitor Closely.

            • haloperidol

              dextromethorphan, haloperidol. unspecified interaction mechanism. Use Caution/Monitor. Serotonin modulators may enhance dopamine blockade, possibly increasing the risk for neuroleptic malignant syndrome. Antipsychotics may enhance serotonergic effect of serotonin modulators, which may result in serotonin syndrome. Monitor for evidence of serotonin toxicity (eg, mental status changes, autonomic instability, and neuromuscular hyperactivity) or neuroleptic malignant syndrome (eg, hyperthermia, muscle rigidity, autonomic dysfunction).

            • iloperidone

              dextromethorphan, iloperidone. unspecified interaction mechanism. Use Caution/Monitor. Serotonin modulators may enhance dopamine blockade, possibly increasing the risk for neuroleptic malignant syndrome. Antipsychotics may enhance serotonergic effect of serotonin modulators, which may result in serotonin syndrome. Monitor for evidence of serotonin toxicity (eg, mental status changes, autonomic instability, and neuromuscular hyperactivity) or neuroleptic malignant syndrome (eg, hyperthermia, muscle rigidity, autonomic dysfunction).

            • isoniazid

              dextromethorphan and isoniazid both increase serotonin levels. Modify Therapy/Monitor Closely.

            • L-tryptophan

              dextromethorphan and L-tryptophan both increase serotonin levels. Modify Therapy/Monitor Closely.

            • letermovir

              letermovir increases levels of dextromethorphan by affecting hepatic/intestinal enzyme CYP3A4 metabolism. Use Caution/Monitor.

            • lithium

              dextromethorphan and lithium both increase serotonin levels. Modify Therapy/Monitor Closely.

            • loxapine

              dextromethorphan, loxapine. unspecified interaction mechanism. Use Caution/Monitor. Serotonin modulators may enhance dopamine blockade, possibly increasing the risk for neuroleptic malignant syndrome. Antipsychotics may enhance serotonergic effect of serotonin modulators, which may result in serotonin syndrome. Monitor for evidence of serotonin toxicity (eg, mental status changes, autonomic instability, and neuromuscular hyperactivity) or neuroleptic malignant syndrome (eg, hyperthermia, muscle rigidity, autonomic dysfunction).

            • loxapine inhaled

              dextromethorphan, loxapine inhaled. unspecified interaction mechanism. Use Caution/Monitor. Serotonin modulators may enhance dopamine blockade, possibly increasing the risk for neuroleptic malignant syndrome. Antipsychotics may enhance serotonergic effect of serotonin modulators, which may result in serotonin syndrome. Monitor for evidence of serotonin toxicity (eg, mental status changes, autonomic instability, and neuromuscular hyperactivity) or neuroleptic malignant syndrome (eg, hyperthermia, muscle rigidity, autonomic dysfunction).

            • lsd

              dextromethorphan and lsd both increase serotonin levels. Modify Therapy/Monitor Closely.

            • lumefantrine

              lumefantrine will increase the level or effect of dextromethorphan by affecting hepatic enzyme CYP2D6 metabolism. Use Caution/Monitor.

            • lurasidone

              dextromethorphan, lurasidone. unspecified interaction mechanism. Use Caution/Monitor. Serotonin modulators may enhance dopamine blockade, possibly increasing the risk for neuroleptic malignant syndrome. Antipsychotics may enhance serotonergic effect of serotonin modulators, which may result in serotonin syndrome. Monitor for evidence of serotonin toxicity (eg, mental status changes, autonomic instability, and neuromuscular hyperactivity) or neuroleptic malignant syndrome (eg, hyperthermia, muscle rigidity, autonomic dysfunction).

            • mirtazapine

              dextromethorphan and mirtazapine both increase serotonin levels. Modify Therapy/Monitor Closely.

            • molindone

              dextromethorphan, molindone. unspecified interaction mechanism. Use Caution/Monitor. Serotonin modulators may enhance dopamine blockade, possibly increasing the risk for neuroleptic malignant syndrome. Antipsychotics may enhance serotonergic effect of serotonin modulators, which may result in serotonin syndrome. Monitor for evidence of serotonin toxicity (eg, mental status changes, autonomic instability, and neuromuscular hyperactivity) or neuroleptic malignant syndrome (eg, hyperthermia, muscle rigidity, autonomic dysfunction).

            • morphine

              dextromethorphan and morphine both increase serotonin levels. Modify Therapy/Monitor Closely.

            • naratriptan

              naratriptan and dextromethorphan both increase serotonin levels. Modify Therapy/Monitor Closely.

            • olanzapine

              dextromethorphan, olanzapine. unspecified interaction mechanism. Use Caution/Monitor. Serotonin modulators may enhance dopamine blockade, possibly increasing the risk for neuroleptic malignant syndrome. Antipsychotics may enhance serotonergic effect of serotonin modulators, which may result in serotonin syndrome. Monitor for evidence of serotonin toxicity (eg, mental status changes, autonomic instability, and neuromuscular hyperactivity) or neuroleptic malignant syndrome (eg, hyperthermia, muscle rigidity, autonomic dysfunction).

            • paliperidone

              dextromethorphan, paliperidone. unspecified interaction mechanism. Use Caution/Monitor. Serotonin modulators may enhance dopamine blockade, possibly increasing the risk for neuroleptic malignant syndrome. Antipsychotics may enhance serotonergic effect of serotonin modulators, which may result in serotonin syndrome. Monitor for evidence of serotonin toxicity (eg, mental status changes, autonomic instability, and neuromuscular hyperactivity) or neuroleptic malignant syndrome (eg, hyperthermia, muscle rigidity, autonomic dysfunction).

            • panobinostat

              panobinostat will increase the level or effect of dextromethorphan by affecting hepatic enzyme CYP2D6 metabolism. Use Caution/Monitor. Panobinostat can increase the levels and effects of sensitive CYP2D6 substrates or those with a narrow therapeutic index CYP2D6.

            • pazopanib

              pazopanib increases levels of dextromethorphan by decreasing metabolism. Use Caution/Monitor.

            • peginterferon alfa 2b

              peginterferon alfa 2b, dextromethorphan. Other (see comment). Use Caution/Monitor. Comment: When patients are administered peginterferon alpha-2b with CYP2D6 substrates, the therapeutic effect of these drugs may be altered. Peginterferon alpha-2b may increase or decrease levels of CYP2D6 substrate.

            • pentazocine

              dextromethorphan and pentazocine both increase serotonin levels. Modify Therapy/Monitor Closely.

            • perphenazine

              dextromethorphan, perphenazine. unspecified interaction mechanism. Use Caution/Monitor. Serotonin modulators may enhance dopamine blockade, possibly increasing the risk for neuroleptic malignant syndrome. Antipsychotics may enhance serotonergic effect of serotonin modulators, which may result in serotonin syndrome. Monitor for evidence of serotonin toxicity (eg, mental status changes, autonomic instability, and neuromuscular hyperactivity) or neuroleptic malignant syndrome (eg, hyperthermia, muscle rigidity, autonomic dysfunction).

            • pimavanserin

              dextromethorphan, pimavanserin. unspecified interaction mechanism. Use Caution/Monitor. Serotonin modulators may enhance dopamine blockade, possibly increasing the risk for neuroleptic malignant syndrome. Antipsychotics may enhance serotonergic effect of serotonin modulators, which may result in serotonin syndrome. Monitor for evidence of serotonin toxicity (eg, mental status changes, autonomic instability, and neuromuscular hyperactivity) or neuroleptic malignant syndrome (eg, hyperthermia, muscle rigidity, autonomic dysfunction).

            • pimozide

              dextromethorphan, pimozide. unspecified interaction mechanism. Use Caution/Monitor. Serotonin modulators may enhance dopamine blockade, possibly increasing the risk for neuroleptic malignant syndrome. Antipsychotics may enhance serotonergic effect of serotonin modulators, which may result in serotonin syndrome. Monitor for evidence of serotonin toxicity (eg, mental status changes, autonomic instability, and neuromuscular hyperactivity) or neuroleptic malignant syndrome (eg, hyperthermia, muscle rigidity, autonomic dysfunction).

            • quetiapine

              dextromethorphan, quetiapine. unspecified interaction mechanism. Use Caution/Monitor. Serotonin modulators may enhance dopamine blockade, possibly increasing the risk for neuroleptic malignant syndrome. Antipsychotics may enhance serotonergic effect of serotonin modulators, which may result in serotonin syndrome. Monitor for evidence of serotonin toxicity (eg, mental status changes, autonomic instability, and neuromuscular hyperactivity) or neuroleptic malignant syndrome (eg, hyperthermia, muscle rigidity, autonomic dysfunction).

            • quinidine

              quinidine will increase the level or effect of dextromethorphan by affecting hepatic enzyme CYP2D6 metabolism. Use Caution/Monitor.

            • risperidone

              dextromethorphan, risperidone. unspecified interaction mechanism. Use Caution/Monitor. Serotonin modulators may enhance dopamine blockade, possibly increasing the risk for neuroleptic malignant syndrome. Antipsychotics may enhance serotonergic effect of serotonin modulators, which may result in serotonin syndrome. Monitor for evidence of serotonin toxicity (eg, mental status changes, autonomic instability, and neuromuscular hyperactivity) or neuroleptic malignant syndrome (eg, hyperthermia, muscle rigidity, autonomic dysfunction).

            • rizatriptan

              rizatriptan and dextromethorphan both increase serotonin levels. Modify Therapy/Monitor Closely.

            • rolapitant

              rolapitant will increase the level or effect of dextromethorphan by affecting hepatic enzyme CYP2D6 metabolism. Modify Therapy/Monitor Closely. Monitor for adverse reactions when unable to avoid coadministration with narrow therapeutic index CYP2D6 substrates.

            • SAMe

              dextromethorphan and SAMe both increase serotonin levels. Modify Therapy/Monitor Closely.

            • sumatriptan

              sumatriptan and dextromethorphan both increase serotonin levels. Modify Therapy/Monitor Closely.

            • sumatriptan intranasal

              sumatriptan intranasal and dextromethorphan both increase serotonin levels. Modify Therapy/Monitor Closely.

            • thiothixene

              dextromethorphan, thiothixene. unspecified interaction mechanism. Use Caution/Monitor. Serotonin modulators may enhance dopamine blockade, possibly increasing the risk for neuroleptic malignant syndrome. Antipsychotics may enhance serotonergic effect of serotonin modulators, which may result in serotonin syndrome. Monitor for evidence of serotonin toxicity (eg, mental status changes, autonomic instability, and neuromuscular hyperactivity) or neuroleptic malignant syndrome (eg, hyperthermia, muscle rigidity, autonomic dysfunction).

            • tramadol

              dextromethorphan and tramadol both increase serotonin levels. Modify Therapy/Monitor Closely.

            • trifluoperazine

              dextromethorphan, trifluoperazine. unspecified interaction mechanism. Use Caution/Monitor. Serotonin modulators may enhance dopamine blockade, possibly increasing the risk for neuroleptic malignant syndrome. Antipsychotics may enhance serotonergic effect of serotonin modulators, which may result in serotonin syndrome. Monitor for evidence of serotonin toxicity (eg, mental status changes, autonomic instability, and neuromuscular hyperactivity) or neuroleptic malignant syndrome (eg, hyperthermia, muscle rigidity, autonomic dysfunction).

            • ziprasidone

              dextromethorphan, ziprasidone. unspecified interaction mechanism. Use Caution/Monitor. Serotonin modulators may enhance dopamine blockade, possibly increasing the risk for neuroleptic malignant syndrome. Antipsychotics may enhance serotonergic effect of serotonin modulators, which may result in serotonin syndrome. Monitor for evidence of serotonin toxicity (eg, mental status changes, autonomic instability, and neuromuscular hyperactivity) or neuroleptic malignant syndrome (eg, hyperthermia, muscle rigidity, autonomic dysfunction).

            • zolmitriptan

              zolmitriptan and dextromethorphan both increase serotonin levels. Modify Therapy/Monitor Closely.

            Minor (22)

            • amiodarone

              amiodarone will increase the level or effect of dextromethorphan by affecting hepatic enzyme CYP2D6 metabolism. Minor/Significance Unknown.

            • asenapine

              asenapine will increase the level or effect of dextromethorphan by affecting hepatic enzyme CYP2D6 metabolism. Minor/Significance Unknown.

            • celecoxib

              celecoxib will increase the level or effect of dextromethorphan by affecting hepatic enzyme CYP2D6 metabolism. Minor/Significance Unknown.

            • chloroquine

              chloroquine will increase the level or effect of dextromethorphan by affecting hepatic enzyme CYP2D6 metabolism. Minor/Significance Unknown.

            • cimetidine

              cimetidine will increase the level or effect of dextromethorphan by affecting hepatic enzyme CYP2D6 metabolism. Minor/Significance Unknown.

            • darifenacin

              darifenacin will increase the level or effect of dextromethorphan by affecting hepatic enzyme CYP2D6 metabolism. Minor/Significance Unknown.

            • diphenhydramine

              diphenhydramine will increase the level or effect of dextromethorphan by affecting hepatic enzyme CYP2D6 metabolism. Minor/Significance Unknown.

            • dronedarone

              dronedarone will increase the level or effect of dextromethorphan by affecting hepatic enzyme CYP2D6 metabolism. Minor/Significance Unknown.

            • haloperidol

              haloperidol will increase the level or effect of dextromethorphan by affecting hepatic enzyme CYP2D6 metabolism. Minor/Significance Unknown.

            • imatinib

              imatinib will increase the level or effect of dextromethorphan by affecting hepatic enzyme CYP2D6 metabolism. Minor/Significance Unknown.

            • maraviroc

              maraviroc will increase the level or effect of dextromethorphan by affecting hepatic enzyme CYP2D6 metabolism. Minor/Significance Unknown.

            • marijuana

              marijuana will increase the level or effect of dextromethorphan by affecting hepatic enzyme CYP2D6 metabolism. Minor/Significance Unknown.

            • nilotinib

              nilotinib will increase the level or effect of dextromethorphan by affecting hepatic enzyme CYP2D6 metabolism. Minor/Significance Unknown.

            • parecoxib

              parecoxib will increase the level or effect of dextromethorphan by affecting hepatic enzyme CYP2D6 metabolism. Minor/Significance Unknown.

            • perphenazine

              perphenazine will increase the level or effect of dextromethorphan by affecting hepatic enzyme CYP2D6 metabolism. Minor/Significance Unknown.

            • propafenone

              propafenone will increase the level or effect of dextromethorphan by affecting hepatic enzyme CYP2D6 metabolism. Minor/Significance Unknown.

            • quinacrine

              quinacrine will increase the level or effect of dextromethorphan by affecting hepatic enzyme CYP2D6 metabolism. Minor/Significance Unknown.

            • ranolazine

              ranolazine will increase the level or effect of dextromethorphan by affecting hepatic enzyme CYP2D6 metabolism. Minor/Significance Unknown.

            • ritonavir

              ritonavir will increase the level or effect of dextromethorphan by affecting hepatic enzyme CYP2D6 metabolism. Minor/Significance Unknown.

            • sertraline

              sertraline will increase the level or effect of dextromethorphan by affecting hepatic enzyme CYP2D6 metabolism. Minor/Significance Unknown.

            • thioridazine

              thioridazine will increase the level or effect of dextromethorphan by affecting hepatic enzyme CYP2D6 metabolism. Minor/Significance Unknown.

            • tipranavir

              tipranavir will increase the level or effect of dextromethorphan by affecting hepatic enzyme CYP2D6 metabolism. Minor/Significance Unknown.

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            Adverse Effects

            Common

            Nausea

            Vomiting

            Constipation

            Drowsiness

            Dizziness

            Sedation

            Confusion

            Nervousness

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            Warnings

            Contraindications

            Concurrent nonselective MAO inhibitors: Serotonin syndrome

            Cautions

            Do not take for persistent or chronic cough associated with smoking, asthma, or emphysema, or if it is accompanied by excessive phlegm unless directed by a healthcare provider; may slow respiration rate

            Hallucinations, confusion, agitation, hyper-reflexia, shivering, myoclonus, and tachycardia may occur

            Caution in children younger than 6 years

            Not for OTC use in children <4 years

            Use caution in patients who are sedated, debilitated or confined to supine position

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            Pregnancy & Lactation

            Pregnancy category: C

            Lactation: Not known if excreted in breast milk; use caution

            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

            Acts on cough center in medulla; decreases sensitivity of cough receptors and interrupts cough impulse transmission

            Derivative of levorphanol

            Absorption

            Onset: 15-30 min

            Duration: ≤6 hr

            Time to peak: 2-3hr

            Metabolism

            Hepatic P450 enzyme CYP2D6

            Elimination

            Half-life: 2-4hr (extensive metabolizers); 24 hr (poor metabolizers)

            Excretion: Urine

            Pharmacogenomics

            CYP2D6 substrate

            Approximately 7-10% of Caucasians and 3-8% of African Americans lack the capacity to metabolize CYP2D6 substrates and are classified as poor metabolizers

            Genetic testing laboratories

            • Genotyping tests for CYP2D6 variants are commercially available through the following companies:
            • Applied Biosystems (http://www.appliedbiosystems.com/)
            • GenPath Diagnostics (http://www.genpathdiagnostics.com/)
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            Images

            No images available for this drug.
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            Patient Handout

            A Patient Handout is not currently available for this monograph.
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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.