Calcitriol
Indications
Calcitriol is used for:
Osteoporosis, Hypoparathyroidism, Hypocalcaemia, Osteomalacia rickets, Renal osteodystrophy, Chronic kidney dialysis.
Adult Dose
Adult: Capsule: The optimal daily dose of Calcitriol must be carefully determined for each patient on the basis of the serum calcium level.
Calcitriol can be administered orally either 0.25 mcg or 0.50 mcg.
Postmenopausal osteoporosis
The recommended dosage is 0.25 mcg twice daily or 0.50 mcg once daily. Serum creatinine levels should be determined at 4 weeks, 3 and 6 months and 6 monthly intervals thereafter.
Renal osteodystrophy (Dialysis patients)
The recommended initial dose of Calcitriol is 0.25 mcg/day. Patients with normal or only slightly reduced serum calcium levels may respond to Calcitriol doses of 0.25 mcg every other day. Most patients undergoing hemodialysis respond to doses between 0.5 and 1 mcg/day.
Hypoparathyroidism & Rickets
The recommended initial dosage of Calcitriol is 0.25 mcg/day given in the morning. If a satisfactory response is not observed, the dose may be increased at 2 to 4 week intervals.
Predialysis patients:
The recommended initial dosage of Calcitriol is 0.25 mcg/day in adults. This dosage may be increased if necessary to 0.5 mcg/day.
Injection
The recommended intravenous initial dose of Calcitriol injection, depending on the severity of the hypocalcemia and/or secondary hyperparathyroidism, is 1 mcg (0.02 mcg/kg) to 2 mcg administered three times weekly, approximately every other day.
Doses as small as 0.5 mcg and as large as 4 mcg three times weekly have been used as an initial dose.
If a satisfactory response is not observed, the dose may be increased by 0.5 to 1 mcg at two to four week intervals.
Child Dose
Chronic Renal Dialysis Associated Hypocalcemia
0.25-2 mcg/day PO qDay
Hypoparathyroidism/Pseudohypoparathyroidism
<1 year: 0.04-0.08 mcg/kg PO qDay
1-5 years: 0.25-0.75 mcg PO qDay
>6 years: 0.5-2 mcg PO qDay
Familial Hypophosphatemia
Initial: 0.015-0.02 mcg/kg PO qDay
Maintenance: 0.03-0.06 mcg/kg PO qDay
No more than 2 mcg PO qDay
Secondary Hyperparathyroidism in Moderate to Severe Kidney Disease
<3 years: 0.01-0.015 mcg/kg/day
>3 years: 0.25 mcg/day PO; may increase to 0.5 mcg/day
Hypocalcemia in Premature Infants
1 mcg qDay PO for 5 days
Renal Dose
Administration
May be taken with or without food. May be taken w/ meals to reduce GI discomfort.
Contra Indications
Hypercalcaemia; evidence of vitamin D toxicity. Pregnancy (dose exceeding RDA). Lactation.
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.
Excessive dosage of Calcitriol induces hypercalcemia and in some instances hypercalciuria; therefore, early in treatment during dosage adjustment, serum calcium should be determined twice weekly.
Patients with normal renal function who are taking Calcitriol should avoid dehydration. Adequate fluid intake should be maintained.
Lactation: Enters breast milk; not recommended
Pregnancy-Lactation
Pregnancy category: C
Lactation: Enters breast milk; not recommended
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.
Side Effects
Side effects of Calcitriol :
Abdominal pain, Apathy, BUN and creatinine increased, Cardiac arrhythmia, Constipation, Dry mouth, Dehydration, Growth suppression, Headache, Hyperthermia, Hypercalcemia, Hypercholesteremia, Hypermagnesemia, Hyperphosphatemia, Hypertension, Libido decreased, Metallic taste, Muscle or bone pain, Nocturia, Pruritus, Psychosis, Somnolence, Weakness
Mode of Action
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..