PARATHAR
Clinical safety rating: caution
Comprehensive clinical and safety monograph for PARATHAR (PARATHAR).
Recombinant human parathyroid hormone (PTH 1-84) that binds to PTH1 receptor, stimulating osteoblast activity and bone formation, increasing bone mineral density.
| Metabolism | Systemic metabolism via nonspecific proteolysis in liver and kidney; no specific CYP450 involvement. |
| Excretion | Renal: 70% unchanged, biliary/fecal: 20% as metabolites, 10% as unchanged drug in feces. |
| Half-life | Terminal half-life: 4-6 hours (prolonged to 10-12 hours in renal impairment; caution in CrCl <30 mL/min). |
| Protein binding | 90-95% bound to albumin and alpha-1-acid glycoprotein. |
| Volume of Distribution | 0.3-0.5 L/kg; indicates distribution primarily into extracellular fluid. |
| Bioavailability | IM: 100%; Subcutaneous: 80-90% (variable due to injection site). |
| Onset of Action | IV: 5-10 minutes; IM: 15-30 minutes; Subcutaneous: 30-60 minutes. |
| Duration of Action | IV: 4-6 hours; IM/Subcutaneous: 6-8 hours; effect on serum calcium lasts up to 12 hours. |
50-100 mcg subcutaneously once daily.
| Dosage form | INJECTABLE |
| Renal impairment | Contraindicated in severe renal impairment (CrCl <30 mL/min). For CrCl 30-60 mL/min, reduce dose to 50 mcg subcutaneously every other day. No adjustment for CrCl >60 mL/min. |
| Liver impairment | No adjustment required for mild to moderate hepatic impairment (Child-Pugh A or B). Not studied in severe hepatic impairment (Child-Pugh C); use with caution. |
| Pediatric use | Safety and efficacy not established in pediatric patients (<18 years). |
| Geriatric use | No specific dose adjustment recommended; monitor serum calcium and phosphate levels more frequently due to age-related renal decline. |
| 1st trimester | Consult provider |
| 2nd trimester | Consult provider |
| 3rd trimester | Consult provider |
Clinical note
Comprehensive clinical and safety monograph for PARATHAR (PARATHAR).
| Breastfeeding | Contraindicated during breastfeeding. Parathyroid hormone-related peptide (PTHrP) is present in milk; M/P ratio not established. Theoretical risk of hypercalcemia in neonate. |
| Teratogenic Risk | FDA Category D. Teratogenic in first trimester, including increased risk of cardiac anomalies. In second and third trimesters, risk of hypercalcemia-related fetal nephrocalcinosis. Avoid in pregnancy unless no alternative. |
| Fetal Monitoring |
■ FDA Black Box Warning
WARNING: Osteosarcoma - In rats, PTH 1-84 caused a dose-dependent increase in osteosarcoma incidence. Avoid in patients at increased risk for osteosarcoma (e.g., Paget's disease, prior radiation).
| Serious Effects |
["Hypersensitivity to parathyroid hormone or any component","Paget's disease of bone","Prior external beam radiation therapy involving the skeleton","Bone metastases or history of skeletal malignancies","Hypercalcemia at baseline","Pregnancy and lactation"]
| Precautions | ["Risk of osteosarcoma (see black box warning)","Hypercalcemia: Monitor serum calcium; dose adjustments may be needed","Hypotension: Transient orthostatic hypotension may occur","Nephrolithiasis: Use caution in patients with active or history of kidney stones","Renal impairment: Safety not established in severe renal impairment"] |
Loading safety data…
| Monitor serum calcium, phosphate, and 1,25-dihydroxyvitamin D levels weekly. Fetal ultrasound for nephrocalcinosis if used beyond first trimester. |
| Fertility Effects | No direct studies on fertility. Potential for ovarian hyperstimulation in women undergoing assisted reproduction if hypercalcemia occurs. |