Calcitriol
Brand Name: Rocaltrol
Generic Available
Common Dosage Forms:
Capsules: 0.25 mcg and 0.5 mcg.
Oral Solutions: 1 mcg/mL
FDA Indications/Dosages:
Management of secondary hyperparathyroidism and resultant metabolic bone disease in patients with moderate to severe chronic renal failure (Ccr 15 to 55 mL/min) not yet on dialysis: 0.25 mcg daily in adults and pediatric patients over 3 years of age. In pediatric patients under 3 years, give 10 to 15 ng/kg/day.
Management of hypocalcemia in patients with postsurgical, idiopathic, and pseudohypoparathyroidism: Start with 0.25 mcg daily and titrate upward at 2-4 week intervals until optimum serum calcium levels are achieved. Usual dosage range is 0.5 to 2 mcg daily.
Management of hypocalcemia are the resultant metabolic bone disease in patients undergoing chronic renal dialysis: Start with 0.25 mcg daily and titrate upward at 4-8 intervals until optimum serum calcium levels are achieved. Usual dosage range is 0.5 to 1 mcg daily.
Pharmacology/Pharmacokinetics: Calcitriol is the active form of vitamin D3 and is formed through conversion of vitamin D3 in the liver and the kidneys. Calcitriol is active in the transportation of calcium through the intestine. Patients with chronic renal failure do not adequately synthesize calcitriol which can then cause hypocalcemia and secondary hyperparathyroidism. This is a major cause of the metabolic bone disease of renal failure. Absorption after an oral dose is rapid with peak plasma levels reached in 3 to 6 hours. Steady-state levels are reached in 7 days after multiple-dose therapy.
Drug Interactions: Cholestyramine may reduce absorption. Phenytoin and phenobarbital may increase metabolism. Thiazides may precipitate hypercalcemia in patients taking calcitriol. Hypercalcemia in patients taking digitalis may precipitate arrhythmias. Avoid vitamin D and magnesium supplements. Avoid calcium supplements outside the amount recommended by a physician.
Contraindications/Precautions: Contraindicated in patients with hypercalcemia and vitamin D toxicity. Excess vitamin D is dangerous and cause progressive hypercalcemia. Therefore avoid vitamin D supplementation in patients taking calcitriol. The serum calcium times phosphate (Ca x P) product should not be allowed to exceed 70 mg2/dL2). Calcitriol increases inorganic phosphate levels in serum. Use phosphate binders or a low-phosphate diet to control levels. Test serum calcium twice weekly early in therapy and daily if calcitriol is withdrawal due to hypercalcemia. Pregnancy Category C.
Adverse Effects: The most common adverse effect are related to vitamin D toxicity and include hypercalcemia syndrome and calcium intoxication. Vitamin D toxicity is first manifested by weakness, headache, somnolence, nausea, vomiting, dry mouth, and anorexia. Late symptoms include polyuria, polydipsia, weight loss, nocturia, conjunctivitis, pancreatitis, photophobia, rhinorrhea, and hyperthermia.
Patient Consultation:
Do not take OTC vitamin D therapy.
Do not exceed prescribed amounts of calcium (800 to 1200 mg daily) from any source.
Do not take OTC magnesium or magnesium containing antacids.
May be taken without regards to meals.
Contact a physician if the above side effects are severe or persistent.
If a dose is missed, take it as soon as possible. If it is closer to the time of your next dose you missed, skip the missed dose and return to your dosing schedule.
Do not discontinue therapy without first consulting physician.
