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Since Rocaltrol (calcitriol) is believed to be the active hormone which exerts vitamin D activity in the body, adverse effects are, in general, similar to those encountered with excessive vitamin D intake, ie, hypercalcemia syndrome or calcium intoxication (depending on the severity and duration of hypercalcemia) (see WARNINGS). Because of the short biological half-life of calcitriol, pharmacokinetic investigations have shown normalization of elevated serum calcium within a few days of treatment withdrawal, ie, much faster than in treatment with vitamin D3 preparations.
The early and late signs and symptoms of vitamin D intoxication associated with hypercalcemia include:
Late: polyuria, polydipsia, anorexia, weight loss, nocturia, conjunctivitis (calcific), pancreatitis, photophobia, rhinorrhea, pruritus, hyperthermia, decreased libido, elevated BUN, albuminuria, hypercholesterolemia, elevated SGOT (AST) and SGPT (ALT), ectopic calcification, nephrocalcinosis, hypertension, cardiac arrhythmias, dystrophy, sensory disturbances, dehydration, apathy, arrested growth, urinary tract infections, and, rarely, overt psychosis.
In clinical studies on hypoparathyroidism and pseudohypoparathyroidism, hypercalcemia was noted on at least one occasion in about 1 in 3 patients and hypercalciuria in about 1 in 7 patients. Elevated serum creatinine levels were observed in about 1 in 6 patients (approximately one half of whom had normal levels at baseline).
Hypersensitivity reactions (pruritus, rash, urticaria, and very rarely severe erythematous skin disorders) may occur in susceptible individuals. One case of erythema multiforme and one case of allergic reaction (swelling of lips and hives all over the body) were confirmed by rechallenge.
Read the Rocaltrol (calcitriol) Side Effects Center for a complete guide to possible side effects
The coadministration of phenytoin or phenobarbital will not affect plasma concentrations of calcitriol, but may reduce endogenous plasma levels of 25(OH)D3 by accelerating metabolism. Since blood level of calcitriol will be reduced, higher doses of Rocaltrol (calcitriol) may be necessary if these drugs are administered simultaneously.
Thiazides are known to induce hypercalcemia by the reduction of calcium excretion in urine. Some reports have shown that the concomitant administration of thiazides with Rocaltrol (calcitriol) causes hypercalcemia. Therefore, precaution should be taken when coadministration is necessary.
Calcitriol dosage must be determined with care in patients undergoing treatment with digitalis, as hypercalcemia in such patients may precipitate cardiac arrhythmias (see PRECAUTIONS: General).
Ketoconazole may inhibit both synthetic and catabolic enzymes of calcitriol. Reductions in serum endogenous calcitriol concentrations have been observed following the administration of 300 mg/day to 1200 mg/day ketoconazole for a week to healthy men. However, in vivo drug interaction studies of ketoconazole with Rocaltrol (calcitriol) have not been investigated.
A relationship of functional antagonism exists between vitamin D analogues, which promote calcium absorption, and corticosteroids, which inhibit calcium absorption.
Since Rocaltrol (calcitriol) also has an effect on phosphate transport in the intestine, kidneys and bones, the dosage of phosphate-binding agents must be adjusted in accordance with the serum phosphate concentration.
Since calcitriol is the most potent active metabolite of vitamin D3, pharmacological doses of vitamin D and its derivatives should be withheld during treatment with Rocaltrol (calcitriol) to avoid possible additive effects and hypercalcemia (see WARNINGS).
Uncontrolled intake of additional calcium-containing preparations should be avoided (see PRECAUTIONS: General).
Read the Rocaltrol Drug Interactions Center for a complete guide to possible interactions
Last reviewed on RxList: 7/17/2008
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