Calcitriol information from DrugsUpdate
P - Contraindicated in pregnancy
L - Contraindicated in pregnancy
Calcitriol is a synthetic vitamin D analog which is active in the regulation of the absorption of calcium from the gastrointestinal tract and its utilization in the body. Calcitriol is available as capsules containing 0.25 mcg or 0.5 mcg Calcitriol and as an oral solution containing 1 mcg/mL of Calcitriol. All dosage forms contain butylated hydroxyanisole (BHA) and butylated hydroxytoluene (BHT) as antioxidants. The capsules contain a fractionated triglyceride of coconut oil, and the oral solution contains a fractionated triglyceride of palm seed oil.
Pharmacodynamics
The two known sites of action of Calcitriol are intestine and bone. A Calcitriol receptor-binding protein appears to exist in the mucosa of human intestine. Additional evidence suggests that Calcitriol may also act on the kidney and the parathyroid glands. Calcitriol is the most active known form of vitamin D3 in stimulating intestinal calcium transport. In acutely uremic rats Calcitriol has been shown to stimulate intestinal calcium absorption.
The kidneys of uremic patients cannot adequately synthesize Calcitriol, the active hormone formed from precursor vitamin D. Resultant hypocalcemia and secondary hyperparathyroidism are a major cause of the metabolic bone disease of renal failure. However, other bone-toxic substances which accumulate in uremia (eg, aluminum) may also contribute.
The beneficial effect of Calcitriol in renal osteodystrophy appears to result from correction of hypocalcemia and secondary hyperparathyroidism. It is uncertain whether Calcitriol produces other independent beneficial effects. Calcitriol treatment is not associated with an accelerated rate of renal function deterioration. No radiographic evidence of extraskeletal calcification has been found in predialysis patients following treatment. The duration of pharmacologic activity of a single dose of Calcitriol is about 3 to 5 days.
Pharmacokinetics
Calcitriol promotes calcium absorption in the intestines and retention at the kidneys thus increasing serum calcium levels. It also increases renal tubule phosphate resorption consequently decreasing serum phosphatase levels, PTH levels and bone resorption.
Absorption
Well absorbed from the GI tract.
Excretion
Mainly excreted in the bile and faeces.
Calcitriol Indications / Calcitriol Uses
Information Not Available
Calcitriol Adverse Reactions / Calcitriol Side Effects
Weakness; headache; somnolence; nausea; vomiting; dry mouth; constipation; muscle pain; bone pain; metallic taste; polyuria; polydipsia; anorexia; irritability; weight loss; nocturia; mild acidosis; reversible azotemia; generalized vascular calcification; nephrocalcinosis; conjunctivitis (calcific); pancreatitis; photophobia; rhinorrhoea; pruritus; hyperthermia; decreased libido; elevated BUN; albuminuria; hypercholesterolaemia; elevated AST and ALT; ectopic calcification; hypertension; cardiac arrhythmias.
Precautions
Monitor
Calcium intake Ensure that patient is receiving an adequate daily intake of calcium. Consider adding a calcium supplement if dietary calcium intake is less than 600 mg/day. Avoid uncontrolled intake. Dialysis patientsEnsure that serum calcium, phosphorous, magnesium, and alkaline phosphatase are determined periodically. Hypercalcemia symptoms Frequently assess patient for signs and symptoms of hypercalcemia (eg, weakness, headache, drowsiness, nausea, vomiting, bone pain, metallic taste, appetite loss, weight loss, polyuria, polydipsia, nocturia, photophobia, mental status change). Hypercalcemic patients Ensure that serum calcium and phosphorous are evaluated daily during periods of hypercalcemia. Hypoparathyroid patients Ensure that serum calcium, phosphorous, and 24-hours urinary calcium are determined periodically. Predialysis patientsEnsure that serum calcium, phosphorous, alkaline phosphatase, creatinine, and intact parathyroid hormone (iPTH) are determined before starting therapy. Thereafter, serum calcium, phosphorous, alkaline phosphatase, and creatinine should be determined monthly for 6 months and then periodically thereafter. The iPTH should be determined every 3 to 4 months. Serum Calcium LevelsEnsure that serum calcium is evaluated before starting therapy, twice weekly during dosage adjustment, and then periodically thereafter, and that blood samples are taken without a tourniquet. If hypercalcemia is noted or if the serum calcium times phosphate product (Ca P) is more than 70, immediately discontinue therapy.
Special Precautions
Idiopathic hypercalcaemia. Pediatric doses must be individualised and monitored under close medical supervision. Coronary disease, renal function impairment and arteriosclerosis, especially in the elderly. Hypoparathyroidism.
Other Drug Interactions
Hypermagnesaemia may develop in patients on chronic renal dialysis. Hypercalcaemia in patients on digitalis may precipitate cardiac arrhythmias. Intestinal absorption of calcitriol may be reduced by cholestyramine and colestipol. Phenytoin, barbiturates may decrease the T1/2 of calcitriol. May develop hypercalcaemia with thiazide diuretics.
Other Interactions
Information Not Available
Dosage
Oral
Hyperparathyroidism in renal failure Adult: 0.25 mcg daily or every other day. May increase by 0.25 mcg daily at intervals of 4-8 weeks. Child: 0.25-2 mcg daily with haemodialysis.
Oral Hypoparathyroidism/pseudohypoparathyroidism Adult: 0.5-2 mcg once daily. Child: 1-5 years: 0.25-0.75 mcg once daily; >6 years: 0.5-2 mcg once daily.
Oral
Vitamin D-resistant rickets (familial hypophosphataemia) Adult: 0.015-0.02 mcg/kg once daily. Maintenance: 0.03-0.06 mcg/kg once daily. Max: 2 mcg once daily. Child: 0.015-0.02 mcg/kg once daily. Maintenance: 0.03-0.06 mcg/kg once daily. Max: 2 mcg once daily.
Oral
Hypocalcaemia in premature infants Child: 1 mg once daily for 5 days.
Intravenous
Hyperparathyroidism in dialysis patients
Adult: 0.5-4 mcg 3 times/weeks, increased if needed in steps of 0.25-0.5 mcg at intervals of 2-4 weeks; max. 8 mcg 3 times/weeks. Child: 1 mcg once daily.
Intravenous
Hyperparathyroidism in renal failure Adult: 0.5 mcg daily 3 times/weeks if undergoing haemodialysis. If necessary, dose can be increased by 0.25-0.5 mcg at intervals of 2-4 weeks. Maintenance: 0.5-3 mcg 3 times/weeks.
Intravenous
Hypocalcaemic tetany in premature infants Child: 0.05 mcg/kg once daily for 5-12 days.
Food(before/after)
May be taken with or without food. (May be taken w/ meals to reduce GI discomfort.)
List of Contraindications
Calcitriol and Pregnancy
Contraindicated in pregnancy
Category C: Either studies in animals have revealed adverse effects on the foetus (teratogenic or embryocidal or other) and there are no controlled studies in women or studies in women and animals are not available. Drugs should be given only if the potential benefit justifies the potential risk to the foetus. If dose > US RDA.
Category D: There is positive evidence of human foetal risk, but the benefits from use in pregnant women may be acceptable despite the risk (e.g., if the drug is needed in a life-threatening situation or for a serious disease for which safer drugs cannot be used or are ineffective).
Calcitriol and Lactation
Contraindicated in lactation
Calcitriol and Children
Safety and efficacy not established in dialysis patients; dosing guidelines for oral calcitriol have not been established in children younger than 1 year of age with hypoparathyroidism or younger than 6 years of age with pseudohypoparathyroidism. Ointment Safety and efficacy not established in children.
Calcitriol and Geriatic
Dose selection should be cautious, starting at the low end of the dosage range.
Calcitriol and Other Contraindications
Hypercalcaemia; evidence of vitamin D toxicity. Pregnancy (dose exceeding RDA). Lactation.
Storage
Intravenous
Store at 15-30
Oral
Store at 15-30
Lab interference
Intravenous
Store at 15-30
Oral
Store at 15-30
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