ZEMPLAR
Clinical safety rating: caution
Comprehensive clinical and safety monograph for ZEMPLAR (ZEMPLAR).
Vitamin D receptor agonist; binds to vitamin D receptors, regulating gene expression of calcium-binding proteins and cellular proliferation/differentiation.
| Metabolism | Metabolized primarily by hepatic enzymes, including CYP24A1 and CYP3A4. |
| Excretion | Primarily hepatobiliary (74% of absorbed dose recovered in feces as parent drug and metabolites); renal excretion accounts for approximately 16% (primarily as metabolites). |
| Half-life | Terminal elimination half-life is 5–7 hours in healthy subjects; prolonged to 14–21 hours in patients with chronic kidney disease stage 5 on hemodialysis, reflecting reduced clearance. |
| Protein binding | >99.8% bound to plasma proteins, primarily to vitamin D-binding protein (DBP) and albumin. |
| Volume of Distribution | 0.3–0.5 L/kg, indicating distribution primarily into extracellular fluid; no extensive tissue binding. |
| Bioavailability | Oral: approximately 95% for the intravenous formulation; the oral capsule has a bioavailability of about 70% due to first-pass metabolism. |
| Onset of Action | Intravenous: 1–2 weeks for reduction of serum PTH in dialysis patients; Oral: 2–4 weeks for suppression of PTH. |
| Duration of Action | Intravenous: Single dose suppresses PTH for at least 24 hours; Oral: Duration of effect is 24–48 hours with repeated dosing. Continued suppression requires maintenance therapy. |
0.04-0.1 mcg/kg IV three times weekly; titrate to serum calcium. Oral: 1-2 mcg daily or 0.5-1 mcg three times weekly.
| Dosage form | SOLUTION |
| Renal impairment | No dose adjustment required for any degree of renal impairment, but monitor calcium and phosphate. |
| Liver impairment | No specific guidelines; use caution in severe hepatic impairment. |
| Pediatric use | IV: 0.04-0.1 mcg/kg three times weekly. Oral: not established for pediatric use. |
| Geriatric use | No specific adjustments; start at lower end of dosing range due to potential age-related decreased renal function. |
| 1st trimester | Consult provider |
| 2nd trimester | Consult provider |
| 3rd trimester | Consult provider |
Clinical note
Comprehensive clinical and safety monograph for ZEMPLAR (ZEMPLAR).
| Breastfeeding | No human data on paricalcitol excretion in breast milk. Based on molecular weight (470.6 Da) and high protein binding (>99%), excretion is likely minimal. M/P ratio unknown. Caution advised due to potential for hypercalcemia in infant if maternal calcium levels are elevated. |
| Teratogenic Risk | Zemplar (paricalcitol) is a vitamin D analog. Limited human data in pregnancy; animal studies show fetal toxicity at high doses. First trimester: possible association with vitamin D analog effects - theoretical risk of fetal hypercalcemia. Second and third trimesters: potential for fetal hypercalcemia and nephrocalcinosis if maternal serum calcium is elevated. Avoid unless benefit outweighs risk. |
■ FDA Black Box Warning
Not applicable; no FDA black box warning for Zemplar.
| Serious Effects |
["Hypercalcemia","Vitamin D toxicity","Hypersensitivity to paricalcitol or any component of the formulation"]
| Precautions | ["Hypercalcemia","Hyperphosphatemia","Adynamic bone disease","Digitalis toxicity risk if hypercalcemia occurs","Monitor serum calcium and phosphate levels"] |
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| Fetal Monitoring | Monitor maternal serum calcium, phosphorus, and intact PTH levels. Fetal monitoring: ultrasound for growth restriction and nephrocalcinosis if prolonged use. Monitor for maternal hypercalcemia. |
| Fertility Effects | No specific human data on fertility effects. Vitamin D analogs may affect calcium homeostasis and potentially impact reproductive function indirectly. Animal studies did not show impaired fertility at clinically relevant doses. |