human parathyroid hormone, recombinant (Rx)

Brand and Other Names:Natpara
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Dosing & Uses

AdultPediatric

Dosage Forms & Strengths

SC injection cartridge

  • 25 mcg/dose
  • 50 mcg/dose
  • 75 mcg/dose
  • 100 mcg/dose

Hypocalcemia

Indicated as an adjunct to calcium and vitamin D to control hypocalcemia in patients with hypoparathyroidism

Dosing guidelines

  • Individualize dose based on total serum calcium (albumin-corrected) and 24-hr urinary calcium excretion
  • The recommended dose is the minimum required to prevent both hypocalcemia and hypercalciuria
  • This dose will generally be the dose that maintains total serum calcium (albumin-corrected) within the lower half of the normal range (ie, 8-9 mg/dL) without the need for active forms of vitamin D and with calcium supplementation sufficient and individualized to meet the patient’s daily requirements
  • Doses of active forms of vitamin D and calcium supplements will need to be adjusted when using recombinant human parathyroid hormone (rhPTH)

Before initiating rhPTH

  • Confirm 25-hydroxyvitamin D stores are sufficient; if insufficient, replace to sufficient levels per standard of care
  • Confirm serum calcium is >7.5 mg/dL

Initiating rhPTH

  • Initial: 50 mcg SC qDay; administer in the thigh (alternate thigh each day)
  • In patients using active forms of vitamin D, decrease the dose of active vitamin D by 50%, if serum calcium is >7.5 mg/dL
  • In patients using calcium supplements, maintain calcium supplement dose
  • Measure serum calcium concentration within 3-7 days
  • Adjust dose of active vitamin D or calcium supplement or both based on serum calcium value and clinical assessment (ie, signs and symptoms of hypocalcemia or hypercalcemia)
  • Suggested adjustments to active vitamin D and calcium supplement based on serum calcium levels are provided below; repeat steps 4 and 5 until target serum calcium levels are within the lower half of the normal range (ie, 8-9 mg/dL), active vitamin D has been discontinued, and calcium supplementation is sufficient to meet daily requirements
  • Vitamin D and calcium dose adjustment
    • Adjust active vitamin D forms first and calcium supplement second
    • Serum calcium >ULN (10.6 mg/dL): Decrease or discontinue vitamin D; decrease calcium supplement
    • Serum calcium >9 mg/dL and
    • Serum calcium ≤9 mg/dL and >8 mg/dL: No change for vitamin D and calcium supplements
    • Serum calcium <8 mg/dL: Increase vitamin D and calcium supplements

rhPTH dose adjustment

  • May increase dose in increments of 25 mcg q4wk; not to exceed 100 mcg/day if serum calcium cannot be maintained >8 mg/dL without an active form of vitamin D and/or oral calcium supplementation
  • May decrease dose to as low as 25 mcg/day if total serum calcium is repeatedly >9 mg/dL after the active form of vitamin D has been discontinued and calcium supplement has been decreased to a dose sufficient to meet daily requirements
  • Monitor clinical response and serum calcium levels after a dosage change
  • Adjust active vitamin D and calcium supplements (as described above) if indicated

rhPTH maintenance dose

  • Maintenance dose should be the lowest dose that achieves a total serum calcium (albumin-corrected) within the lower half of the normal total serum calcium range (ie, ~8-9 mg/dL), without the need for active forms of vitamin D and with calcium supplementation sufficient to meet daily requirements
  • Monitor serum calcium and 24-hour urinary calcium per standard of care once a maintenance dose is achieved

rhPTH dose interruption or discontinuation

  • Abrupt interruption or discontinuation of rhPTH can result in severe hypocalcemia
  • Resume treatment with, or increase the dose of, an active form of vitamin D and calcium supplements if indicated in patients interrupting or discontinuing rhPTH
  • Monitor for signs and symptoms of hypocalcemia and serum calcium levels
  • In the case of a missed dose, the next rhPTH dose should be administered as soon as reasonably feasible and additional exogenous calcium should be taken in the event of hypocalcemia

Dosage Modifications

Hepatic impairment

  • Mild-to-moderate (Child-Pugh A or B): No dose adjustment required
  • Severe (Child-Pugh C): Data are not available

Renal impairment

  • Mild-to-moderate (CrCl 30-90 mL/min): No dose adjustment required
  • Severe (CrCl <30 mL/min), ESRD, dialysis: Data are not available

Dosing Considerations

Because of the potential risk of osteosarcoma, recommended only for patients who cannot be well-controlled on calcium supplements and active forms of vitamin D alone

Not studied in patients with hypoparathyroidism caused by surgery or calcium-sensing receptor mutations

<18 years: Safety and efficacy not established

Avoid use in patients who are at increased baseline risk for osteosarcoma, including pediatric and young adult patients with open epiphyses

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Interactions

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            Contraindicated (5)

            • alendronate

              alendronate decreases effects of human parathyroid hormone, recombinant by Other (see comment). Contraindicated. Comment: Coadministration of bisphosphonates with rhPTH leads to reduction in rhPTH's calcium sparing effect, which can interfere with the normalization of serum calcium.

            • etidronate

              etidronate decreases effects of human parathyroid hormone, recombinant by Other (see comment). Contraindicated. Comment: Coadministration of bisphosphonates with rhPTH leads to reduction in rhPTH's calcium sparing effect, which can interfere with the normalization of serum calcium.

            • ibandronate

              ibandronate decreases effects of human parathyroid hormone, recombinant by Other (see comment). Contraindicated. Comment: Coadministration of bisphosphonates with rhPTH leads to reduction in rhPTH's calcium sparing effect, which can interfere with the normalization of serum calcium.

            • risedronate

              risedronate decreases effects of human parathyroid hormone, recombinant by Other (see comment). Contraindicated. Comment: Coadministration of bisphosphonates with rhPTH leads to reduction in rhPTH's calcium sparing effect, which can interfere with the normalization of serum calcium.

            • zoledronic acid

              zoledronic acid decreases effects of human parathyroid hormone, recombinant by Other (see comment). Contraindicated. Comment: Coadministration of bisphosphonates with rhPTH leads to reduction in rhPTH's calcium sparing effect, which can interfere with the normalization of serum calcium.

            Serious - Use Alternative (1)

            • digoxin

              human parathyroid hormone, recombinant, digoxin. Other (see comment). Avoid or Use Alternate Drug. Comment: rhPTH causes transient increase in calcium and therefore, concomitant use with cardiac glycosides may predispose patients to digitalis toxicity if hypercalcemia develops. Digoxin efficacy is reduced if hypocalcemia is present. If coadministered, carefully monitor serum calcium and digoxin levels, and patients for signs and symptoms of digoxin toxicity. Adjustment of digoxin and/or rhPTH dose may be needed.

            Monitor Closely (0)

              Minor (0)

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                Adverse Effects

                >10%

                Paraesthesia (31%)

                Hypocalcemia (27%)

                Headache (25%)

                Hypercalcemia (19%)

                Nausea (18%)

                Hypoaesthesia (14%)

                Diarrhea (12%)

                Vomiting (12%)

                Arthralgia (11%)

                Hypercalciuria (11%)

                1-10%

                Pain in extremity (10%)

                Upper respiratory tract infection (8%)

                Abdominal pain upper (7%)

                Sinusitis (7%)

                Blood 25-hydroxycholecalciferol decreased (6%)

                Hypertension (6%)

                Hypoaesthesia facial (6%)

                Neck pain (6%)

                Postmarketing Reports

                Hypersensitivity reactions

                Seizures (due to hypocalcemia)

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                Warnings

                Black Box Warnings

                Because of the potential risk of osteosarcoma, prescribe only to patients who cannot be well-controlled on calcium and active forms of vitamin D and for whom the potential benefits are considered to outweigh the potential risk

                Available only through a restricted program called the NATPARA REMS Program; further information is available at www.NATPARAREMS.com or by telephone at 1-855-NATPARA (1-855-628-7272)

                Avoid with increased osteosarcoma risk

                • Paget disease of bone or unexplained elevations of alkaline phosphatase
                • Pediatric and young adult patients with open epiphyses
                • Hereditary disorders predisposing to osteosarcoma
                • History of prior external beam or implant radiation therapy involving the skeleton

                Contraindications

                Hypersensitivity to drug or excipients

                Cautions

                Potential increased risk of osteosarcoma (see Black Box Warnings)

                Hypersensitivity reactions, including anaphylaxis, dyspnea, angioedema, urticaria, and rash reported; if signs or symptoms of serious hypersensitivity reaction occur, discontinue treatment and treat hypersensitivity reaction according to standard of care; monitor until signs and symptoms resolve; monitor for hypocalcemia if therapy discontinued

                Severe hypercalcemia reported; the risk is highest when starting or increasing the dose; monitor serum calcium and patients for signs and symptoms of hypercalcemia; monitor serum calcium when starting or adjusting dose and when making changes to co-administered drugs known to raise serum calcium

                Severe hypocalcemia that resulted in seizures reported; the risk is highest when a rhPTH dose is withheld, missed, or abruptly discontinued, but can occur at any time; monitor for signs and symptoms of hypocalcemia

                Monitor digoxin levels if coadministered; the inotropic effects of digoxin are affected by serum calcium levels; hypercalcemia of any cause may predispose to digoxin toxicity; monitor serum calcium more frequently and increase monitoring when initiating or adjusting dose

                Coadministration with alendronate leads to reduction in the calcium-sparing effect, which can interfere with the normalization of serum calcium; concomitant use with alendronate is not recommended

                REMS Program

                • Because of potential risk of osteosarcoma associated with therapy, drug is available only through restricted REMS program; under the program, only certified healthcare providers can prescribe and only certified pharmacies can dispense the drug; further information is available at www.NATPARAREMS.com or by telephone at 1-800-828-2088
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                Pregnancy & Lactation

                Pregnancy

                Available data with injection use in pregnant women are insufficient to inform a drug-associated risk of birth defects, miscarriage or adverse maternal or fetal outcomes; there are no adequate and well-controlled studies in pregnant women

                Maternal hypocalcemia can result in an increased rate of spontaneous abortion, premature and dysfunctional labor, and possibly preeclampsia

                Infants born to mothers with hypocalcemia can have associated fetal and neonatal hyperparathyroidism, which in turn can cause fetal and neonatal skeletal demineralization, subperiosteal bone resorption, osteitis fibrosa cystica and neonatal seizures

                Infants born to mothers with hypocalcemia should be carefully monitored for signs of hypocalcemia or hypercalcemia, including neuromuscular irritability (ranging from myotonic jerks to seizures), apnea, cyanosis and cardiac rhythm disorders

                Animal Data

                • Because animal reproduction studies are not always predictive of human response, use during pregnancy only if the potential benefit justifies the potential risk to the fetus
                • No adverse developmental effects were observed when pregnant rats and rabbits were administered parathyroid hormone subcutaneously during period of organogenesis at doses resulting in 123 times and 8 times, respectively, the human exposure at the 100 mcg/day clinical dose
                • Developmental effects were observed in a perinatal/postnatal study in pregnant rats given SC doses of 100, 300, 1000 mcg/kg/day from organogenesis through lactation, entire stillborn litters were observed in the 300-mcg/kg/day group (34 times the 100-mcg/day clinical dose based on AUC)
                • Increased incidence of morbidity associated with dehydration, broken palate, and palate injuries related to incisor misalignment and mortality were found in pups from litters given 100 mcg/kg/day (10 times the 100-mcg/day clinical dose based on AUC)

                Lactation

                There are no data available on presence of parathyroid hormone in breast milk, effects on breastfed infant or on milk production; parathyroid hormone is present in the milk of lactating rats; when a drug is present in animal milk, it is likely that the drug will be present in human milk

                The developmental and health benefits of breastfeeding should be considered along with mother’s clinical need for therapy and any potential adverse effects on breastfed child from drug or from underlying maternal condition

                Infants exposed to parathyroid hormone through breast milk should be monitored for signs and symptoms of hypercalcemia or hypocalcemia; monitoring of serum calcium in the infant should be considered

                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

                Bioengineered replica of human parathyroid hormone 1-84 (rhPTH 1-84)

                Parathyroid hormone raises serum calcium by increasing renal tubular calcium reabsorption, increasing intestinal calcium absorption (ie, by converting 25 OH vitamin D to 1,25 OH2 vitamin D), and increasing bone turnover, which releases calcium into the circulation

                Absorption

                Bioavailability: 53%

                Peak plasma concentration: 5-30 min; second small peak at 1-2 hr

                Distribution

                Vd: 5.35 L (steady state)

                Metabolism

                Primarily via hepatic clearance; most of the intact PTH is cleaved by cathepsins

                Elimination

                Half-life: ~3 hr

                Excretion: A small amount of PTH binds to physiologic PTH-1 receptors, but most is filtered at the glomerulus; C-terminal fragments are also cleared efficiently by glomerular filtration

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                Administration

                SC Preparation

                Supplied as a multiple dose, dual-chamber glass cartridge containing a sterile powder and diluent in 4 dosage strengths

                Reconstitute each cartridge using the mixing device for reconstitution Inspect visually for particulate matter and discoloration prior to administration

                Discard the needle in a puncture-resistant container following administration

                After reconstitution, each medication cartridge can be used for 14 SC injections

                SC Administration

                Administer SC by using the pen delivery device (ie, Q-Cliq pen)

                Administer in thigh, rotating between thighs for each dose

                Storage

                The mixing device and empty Q-Cliq pen can be stored at room temperature

                Store away from heat and light; avoid exposure to elevated temperatures

                Do not freeze or shake; do not use if it has been frozen or shaken

                Unreconstituted cartridges

                • Refrigerate at 36-46°F (2-8°C)
                • Store away from heat and light; avoid exposure to elevated temperatures
                • Do not freeze or shake
                • Do not use if it has been frozen or shaken

                Reconstituted cartridge

                • Refrigerate (36-46°F [2-8°C]) the remaining reconstituted doses in the Q-Cliq pen for up to 14 days
                • After the 2-wk use period, only the cartridge should be discarded (ie, do not discard Q-Cliq pen)
                • The Q-Cliq pen can be used for up to 2 years by replacing the reconstituted medication cartridges q2wk
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                Images

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                Patient Handout

                Patient Education
                parathyroid hormone subcutaneous

                PARATHYROID HORMONE - SUBCUTANEOUS INJECTION

                (PAR-a-THYE-roid HOR-mone)

                COMMON BRAND NAME(S): Natpara

                WARNING: This medication has caused an increase in a type of bone cancer (osteosarcoma) in rats. It is unknown if it will increase the chance of bone cancer in humans. Before using this medication, tell your doctor or pharmacist your medical history, especially of Paget's disease or other bone disease, increase in a certain enzyme in your blood (alkaline phosphatase), personal/family history of bone cancer, or radiation treatment. Talk with your doctor about the benefits and risks of using this medication.This medication should not be used by children and young adults whose bones are still growing, since they might have an increased risk of bone cancer.In the United States, all doctors, pharmacies, and patients must follow the requirements of the Natpara REMS Program to receive this medication. If you live in Canada or any other country, ask your doctor and pharmacist for your country's requirements.

                USES: This medication is a man-made form of parathyroid hormone, a natural substance made in your body by the parathyroid glands. Parathyroid hormone helps to regulate and maintain the balance of calcium and phosphorus in your body. This medication is used along with calcium and vitamin D to help control low blood calcium due to low levels of parathyroid hormone.

                HOW TO USE: Read the Medication Guide and Instructions for Use provided by your pharmacist before you start using parathyroid hormone and each time you get a refill. If you have any questions, ask your doctor or pharmacist.If you are using this medication at home, learn all preparation and usage instructions from your health care professional and the product package. Before using, check this product visually for particles or discoloration. If either is present, do not use the liquid.Before injecting each dose, clean the injection site with rubbing alcohol. Avoid areas of the skin that are red or irritated. Change the injection site each time to lessen injury under the skin.Inject this medication under the skin of your thigh as directed by your doctor, usually once daily. Change the injection site to the opposite leg each day.The dosage is based on your medical condition and response to treatment. Do not stop using or change your dose of parathyroid hormone unless your doctor tells you to. Your calcium level could become too low or too high, causing serious side effects (see also Side Effects section). Your doctor will adjust your doses of vitamin D and calcium supplements while you are using this medication. Carefully follow your doctor's instructions for all your medications.Use this medication regularly to get the most benefit from it. To help you remember, use it at the same time each day.Learn how to store and discard medical supplies safely.Tell your doctor if your condition does not improve or if it worsens.

                SIDE EFFECTS: Skin tingling, tickling, or a burning feeling may occur. Nausea, vomiting, or diarrhea may also occur. If any of these effects persist or worsen, tell your doctor or pharmacist promptly.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.High blood calcium can occur, especially when you first start using this medication. Tell your doctor right away if you have symptoms such as constipation, abdominal pain, unusual thirst, frequent urination, or muscle weakness.Low blood calcium can also occur, especially if you stop using or miss a dose of this medication. Tell your doctor right away if you develop symptoms of low blood calcium, such as tingling of your lips/tongue/fingers/feet, twitching of face muscles, cramps in your feet/hands, seizures, depression, or having problems thinking or remembering.A very serious allergic reaction to this drug is rare. However, get medical help right away 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: See also Warning section.Before using man-made parathyroid hormone, 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.Before having surgery, tell your doctor or dentist about all the products you use (including prescription drugs, nonprescription drugs, and herbal products).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.

                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.

                NOTES: Do not share this medication with others.Laboratory and/or medical tests (such as calcium/phosphorus/vitamin D blood levels, urinary calcium) must be performed before you start treatment, periodically to monitor your progress, or to check for side effects. Consult your doctor for more details.

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

                STORAGE: Store in the refrigerator away from light and moisture. Do not freeze or shake. Do not store in the bathroom. Keep all medications away from children and pets. Discard the mixed product (cartridge) after 14 days. The device can be used for up to 2 years.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

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                Tier Description
                1 This drug is available at the lowest co-pay. Most commonly, these are generic drugs.
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