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What is calcitriol, and how does it work (mechanism of action)?
Calcitriol is a synthetic (man-made) active form of
vitamin D3 (cholecalciferol). It is used to treat and prevent low levels of
calcium in the blood of patients who have kidney disease or problems with their
parathyroid gland, the gland that controls the amount of calcium in blood
through its secretion of parathyroid hormone.
Calcium plays an important role in maintaining bone health, and low levels of
calcium may cause bone disease. Calcitriol increases blood levels of calcium by
increasing the absorption of calcium in the kidneys, increasing the absorption
of calcium and phosphorus from the intestine, and increasing the release of
calcium and phosphorus from the bones. Calcitriol helps the body to use calcium
found in foods and supplements.
What brand names are available for calcitriol?
Rocaltrol
Is calcitriol available as a generic drug?
Yes
Do I need a prescription for calcitriol?
Yes
What are the side effects of calcitriol?
WARNING
Excessive vitamin D may lead to hypercalcemia
(abnormally high levels of calcium in the blood), hypercalciuria (elevated
levels of calcium in the urine), hyperphosphatemia (high levels of phosphate in
the blood), and bone disease. To avoid complications, vitamin D and its
derivatives should be avoided during calcitriol therapy.
Hypercalcemia has been reported in patients
treated with calcitriol. Patients should avoid making any sudden changes in
their dietary calcium intake and maintain adequate intake of fluid (hydration)
during treatment.
Which drugs or supplements interact with calcitriol?
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.
QUESTION
According to the USDA, there is no difference between a “portion” and a “serving.”
See Answer
What is the dosage for calcitriol?
- The recommended initial oral dose for treating low calcium due to kidney
dialysis is 0.25 mcg daily. - The dose may be increased by 0.25 mcg daily every 4
to 8 weeks. - Most patients respond to 0.5 to 1 mcg daily.
- The oral dose for treating hypoparathyroidism is 0.25 mcg to 2 mcg daily.
Is calcitriol safe to take if I’m pregnant or breastfeeding?
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.
Calcitriol may be excreted in human milk. Mothers should not
breastfeed while taking calcitriol.
What else should I know about calcitriol?
What preparations of calcitriol are available?
- Oral liquid filled capsules: 0.25 and 0.5 mcg
- Oral solution: 1 mcg/ml
- Solution for injection: 1 and 2 mcg/ml
How should I keep calcitriol stored?
Calcitriol should be stored at room temperature, between 15 C and 30
C (59 F and 86 F). Protect from light.