Calcitriol should not be used with other vitamin D products because of the increased risk of additive side effects and toxicity.
Cholestyramine (Questran), colestipol (Colestid), mineral oil, and orlistat (Alli, Xenical) may decrease the intestinal absorption of calcitriol. Separating the administration of these medications and calcitriol may prevent this interaction.
Phenytoin (Dilantin) and phenobarbital (Luminal) may reduce blood concentrations of calcitriol, decreasing treatment effectiveness. Higher doses of calcitriol may be necessary if these drugs are used together with calcitriol.
Thiazide diuretics may increase the blood levels of calcium. Since calcitriol also increases calcium levels, taking these two types of medications together may cause hypercalcemia (abnormally highly levels of calcium).
Calcitriol should be used cautiously in patients taking digoxin (Lanoxin). High levels of calcium may cause symptoms of digoxin toxicity such as irregular heartbeats.
Ketoconazole (Nizoral) may decrease the activity of enzymes responsible for metabolizing or breaking down calcitriol and lead to the side effects of excessive vitamin D.
Magnesium containing medications (for example, antacids) should be avoided in patients undergoing chronic renal dialysis who are taking calcitriol. These patients are at high risk of experiencing hypermagnesemia (high blood levels of magnesium) as their kidneys are unable to remove adequate amounts of magnesium from the blood.
PREGNANCY: There are no adequate and well-controlled studies of calcitriol treatment in pregnant women. Calcitriol should be used during pregnancy only if the potential benefit justifies the potential risk to the unborn baby.
NURSING MOTHERS: Calcitriol may be excreted in human milk. Mothers should not breastfeed while taking calcitriol.
REFERENCE: FDA Prescribing Information
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