Calcitriol is one of the most important active metabolites of vitamin D3. It is normally formed in the kidneys from its precursor, 25-hydroxycholecalciferol. Calcitriol promotes intestinal absorption of calcium and regulates bone mineralization. The key role of Calcitriol is the regulation of calcium homeostasis, which includes stimulation effects on osteoblastic activity in the skeleton.
Concomitant treatment with a thiazide diuretics increases the risk of hypercalcemia. Calcitriol dosage must be determined with care in patients undergoing treatment with digitalis as hypercalcemia in such patients may precipitate cardiac arrhythmias. Magnesium containing drugs (e.g.,antacids) may cause hypermagnesemia.
Calcitriol is contraindicated in patients with known hypersensitivity to any of its ingredients. Calcitriol is also contraindicated in all diseases associated with hypercalcemia.
Occasional symptoms include anorexia, headache, vomiting and constipation. Chronic effects may include dystrophy, fever, polyuria, dehydration, apathy and urinary tract infection.
There is no evidence that vitamin D is teratogenic in humans. Calcitriol may be used during pregnancy only if the benefits outweigh the potential risk to the fetus. Mothers may breast feed while taking Calcitriol but serum calcium levels of the mother and infant should be monitored.
During Calcitriol therapy if the serum calcium levels rise to 1 mg/100 ml above normal or serum creatinine rises to >120 µmol/l, the dosage of Calcitriol should be substantially reduced or treatment stopped.
Secondary hyperparathyroidism in patients with moderate to severe chronic renal failure (pre-dialysis)-
The recommended initial dosage of Calcitriol is 0.25 mcg/day in adults and pediatric patients 3 years of age or older. This dosage may be increased if necessary to 0.5 mcg/day.
For pediatric patients less than 3 years of age, the recommended initial dosage of Calcitriol is 10 to 15 ng/kg/day.
In Elderly: No dosage adjustment are required.
