CALCIJEX
Clinical safety rating: caution
Comprehensive clinical and safety monograph for CALCIJEX (CALCIJEX).
Calcitriol, the active form of vitamin D, binds to the vitamin D receptor (VDR) in target tissues, increasing intestinal absorption of calcium and phosphate, promoting renal tubular reabsorption of calcium, and stimulating bone resorption. It also suppresses parathyroid hormone (PTH) synthesis and secretion via negative feedback.
| Metabolism | Primarily hepatic via 24-hydroxylation; also undergoes further oxidation and conjugation. Not significantly metabolized by CYP450 enzymes. |
| Excretion | Primarily hepatic (biliary-fecal) elimination; approximately 2-4% excreted unchanged in urine. Small amount undergoes enterohepatic recirculation. |
| Half-life | Terminal elimination half-life ranges from 5 to 10 hours in patients with normal renal function. In renal impairment, half-life may be prolonged up to 20 hours or more. |
| Protein binding | Approximately 99.9% bound to vitamin D-binding protein (DBP) and albumin. |
| Volume of Distribution | Volume of distribution (Vd) is approximately 0.25 L/kg (range 0.2-0.3 L/kg). This low Vd indicates distribution mainly to extracellular fluid and tissues. |
| Bioavailability | Oral bioavailability is approximately 60-70% when administered as the injectable formulation orally; however, for IV administration, bioavailability is 100%. |
| Onset of Action | Intravenous: Onset of action occurs within 1 to 2 hours after administration, with peak effect on intestinal calcium transport seen at 6 hours. |
| Duration of Action | Duration of action is approximately 3 to 5 days for effects on calcium levels, but may persist longer due to effects on bone metabolism. Clinical monitoring of serum calcium and phosphate is required. |
Intravenous: 0.5 mcg three times per week during dialysis; may be increased by 0.25-0.5 mcg at 2-4 week intervals. Oral: 0.25 mcg daily; may be increased to 0.5 mcg daily.
| Dosage form | INJECTABLE |
| Renal impairment | For GFR < 30 mL/min: reduce initial dose to 0.25 mcg oral or 0.5 mcg IV three times weekly. No adjustment for GFR > 30 mL/min. |
| Liver impairment | No specific recommendations for Child-Pugh classes; caution in severe hepatic impairment due to risk of accumulation. |
| Pediatric use | Intravenous: 0.01-0.05 mcg/kg three times weekly; titrate based on calcium and PTH levels. Oral: 0.015-0.025 mcg/kg once daily. |
| Geriatric use | Start at low end of dosing range (0.25 mcg oral or 0.25-0.5 mcg IV three times weekly); monitor calcium and phosphate closely due to increased sensitivity. |
| 1st trimester | Consult provider |
| 2nd trimester | Consult provider |
| 3rd trimester | Consult provider |
Clinical note
Comprehensive clinical and safety monograph for CALCIJEX (CALCIJEX).
| Breastfeeding | Calcitriol is excreted into human breast milk but in low amounts. No adverse effects reported in nursing infants. The M/P ratio is not established. Caution is advised due to risk of hypercalcemia in the infant; monitor infant serum calcium if maternal use is necessary. |
| Teratogenic Risk | Calcitriol (CALCIJEX) is a Vitamin D analog. Based on animal studies, there is evidence of teratogenicity at high doses (skeletal abnormalities, reduced fetal weight). Human data are limited. Pregnancy Category C. First trimester: Theoretical risk of teratogenicity if hypercalcemia occurs; avoid excessive doses. Second and third trimesters: Risk of fetal hypercalcemia and suppression of parathyroid function if maternal hypercalcemia develops; use only if clearly needed and monitor maternal calcium levels. |
■ FDA Black Box Warning
None
| Serious Effects |
Hypercalcemia, vitamin D toxicity, known hypersensitivity to calcitriol or any component of the formulation.
| Precautions | Hypercalcemia, hypercalciuria, hyperphosphatemia; aluminum hydroxide use may increase aluminum absorption; avoid vitamin D supplementation; monitor serum calcium and phosphate levels regularly; caution in patients with coronary artery disease (calcium load). |
| Food/Dietary | Avoid excessive dietary calcium (dairy products, fortified foods) during treatment. Do not take calcium-containing antacids or supplements. Maintain adequate fluid intake to prevent hypercalcemia. |
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| Fetal Monitoring | Monitor maternal serum calcium, phosphate, and magnesium levels regularly; monitor for signs of hypercalcemia. Fetal monitoring: consider fetal ultrasound for skeletal development if used long-term. Neonatal monitoring: assess serum calcium and parathyroid hormone at birth. |
| Fertility Effects | No specific studies on fertility effects in humans. In animal studies, high doses of calcitriol did not impair fertility. However, hypercalcemia can affect reproductive function; maintain normocalcemia. |
| Clinical Pearls |
| Monitor serum calcium and phosphate levels closely; hypercalcemia risk is highest with concurrent thiazide use or high calcium intake. Adjust dose based on PTH levels in CKD patients. Use with caution in digitalis-treated patients due to additive positive inotropic effect. |
| Patient Advice | Take this medication exactly as prescribed; do not change dose or frequency without consulting your doctor. · Alert your doctor if you experience symptoms of high calcium: nausea, vomiting, constipation, muscle weakness, or confusion. · Avoid excessive intake of calcium-rich foods, supplements, or antacids during treatment. · You may need regular blood tests to monitor calcium, phosphate, and parathyroid hormone levels. · Inform all healthcare providers that you are taking Calcijex. |