calcifediol
Calderol

Available forms
Available by prescription only
Capsules: 20 mcg, 50 mcg

Indications and dosages
 Management of metabolic bone disease or hypocalcemia in patients on long-term renal dialysis. Adults: Initially, 300 to 350 mcg/week P.O. given daily or every other day. May increase dosage at 4-week intervals based on serum levels. Most patients respond to 50 to 100 mcg daily or 100 to 200 mcg every other day.

Pharmacodynamics
Antihypocalcemic action: Vitamin D analogue (25-hydroxycholecalciferol) that works with parathyroid hormone to regulate serum calcium; drug must be activated for its full effect, but appears to have some intrinsic activity.

Pharmacokinetics
Absorption: Absorbed readily from small intestine.
Distribution: Distributed widely; highly protein-bound.
Metabolism: Metabolized in liver and kidney; half-life is 16 days. It’s activated to 1,25 dihydroxycholecalciferol.
Excretion: Excreted in urine and bile.

Contraindications and precautions
Contraindicated in patients with hypercalcemia or vitamin D toxicity.

Interactions
Drug-drug. Antacids, mineral oil: May alter calcifediol absorption. Don’t use together.
Barbiturates, phenytoin, primidone: May increase metabolism and reduce activity of calcifediol. Monitor patient closely.
Cardiac glycosides: Increases effect of cardiac glycosides. Monitor patient closely.
Cholestyramine, colestipol hydrochloride: May reduce intestinal absorption. Separate administration times.
Corticosteroids: Counteracts effects of vitamin D analogues. Don’t use together, if possible.
Thiazide diuretics: May result in hypercalcemia. Monitor serum calcium level.

Adverse reactions
Adverse reactions stem from vitamin D intoxication related to hypercalcemia.
CNS: headache, somnolence, weakness, irritability.
CV: hypertension, arrhythmias.
EENT: conjunctivitis, rhinorrhea.
GI: constipation, nausea, vomiting, polydipsia, pancreatitis, metallic taste, dry mouth, anorexia, diarrhea.
GU: polyuria, nocturia, nephrocalcinosis.
Metabolic: weight loss.
Musculoskeletal: bone and muscle pain.
Skin: pruritus, photosensitivity.
Other: hyperthermia, decreased libido.

Effects on lab test results
None reported.

Overdose and treatment
Only sign of overdose is hypercalcemia. Severe overdose has led to death from cardiac and renal failure.
 Treatment involves discontinuing therapy, instituting a low-calcium diet, and increasing fluid intake. Provide supportive measures.

Special considerations
• Calcitonin administration may be useful in treating hypercalcemia.
• Calciferol may falsely elevate cholesterol determinations using the Zlatkis-Zak reaction.
• Before starting therapy, verify that serum phosphate levels are controlled. To avoid ectopic calcification, serum calcium (mg/dl) times phosphorus (mg/dl) shouldn’t exceed 70.
• Monitor serum calcium levels several times weekly when starting therapy.
• Monitoring urine calcium and urine creatinine may be very helpful in screening for hypercalciuria. Ratio of urine calcium to urine creatinine should be less than or equal to 0.18. A value above 0.2 suggests hypercalciuria; dose should be decreased regardless of serum calcium level.
Breast-feeding patients
• Very little drug appears in breast milk; however, the effect of vitamin D levels that exceed the RDA in infants is unknown. Use drug cautiously in breast-feeding women.
Pediatric patients
• Some infants may be hyperreactive to drug.

Patient education
• Explain importance of a calcium-rich diet.

Reactions may be common, uncommon, life-threatening, or COMMON AND LIFE THREATENING.
◆ Canada only
◇ Unlabeled clinical use