Calcitriol
Synonym :
1,25-dihydroxycholecalciferol
Mechanism :
It is a vitamin D derivative. It is also known as 1-25 DIHYDROXYCHOLECALCIFEROL
Natural supply of vitamin D depends mainly on exposure to the ultraviolet rays of the sun for conversion of 7-dehydrocholesterol in the skin to vitamin D3 (cholecalciferol). Vitamin D3 is then activated in the liver and the kidney before it is fully active at target tissues.
Indication :
- Vitamin D dependent rickets
- Hypophosphatemic rickets
- Hypoparathyroidism/Pseudohypoparathyroidism
- Familial Hypophosphatemia
- Hypocalcemia in premature infants
- Renal osteodystrophy
- Dialysis associated Hypocalcemia
- Secondary hyperparathyroidism in moderate to severe kidney disease
Contraindications :
Should not be given to patients with hypercalcemia or evidence of vitamin D toxicity. Also avoid in patients with hypersensitivity to calcitriol, and use with caution along with other food supplements etc.
Dosing :
0.25 mcg or 0.50 mcg capsules.
Hypocalcemia secondary to hypoparathyroidism:
Oral: 1 mcg once daily for the first 5 days of life.
Hypocalcemic tetany:
IV: 0.05 mcg/kg once daily for 5 to 12 days.
Oral: Initial: 0.25 mcg/dose once daily, followed by 0.01 to 0.15 mcg/kg/day divided in 2 doses. Maximum daily dose: 2 mcg).
Secondary hyperparathyroidism in patients with chronic kidney disease (CKD)
CKD Stages 2 to 4:
Oral
<3 years:
0.01 to 0.15 mcg/kg/day PO daily (evaluate dosage at 2- to 4-week intervals).
3 years and above:
0.25-0.5 mcg PO daily (evaluate dosage at 2- to 4-week intervals).
Renal failure on dialysis:
1 to 5 years:
0.25 to 2 mcg once daily (evaluate dosage at 2- to 4-week intervals).
≥6 years:
0.25 to 1 mcg once daily.
Hypoparathyroidism/pseudohypoparathyroidism:
Oral
Infants:
0.04 to 0.08 mcg/kg once daily.
1 to 5 years:
0.25 to 0.75 mcg once daily (evaluate dosage at 2- to 4-week intervals).
≥6 years:
0.5 to 2 mcg once daily.
Vitamin D dependent rickets:
Oral
One mcg PO OD.
Familial Hypophosphatemia:
0.015 to 0.02 mcg/kg/day PO daily. Max: 2 mcg/day.
Adverse Effect :
Hypercalcemia syndrome: Weakness, headache, somnolence, nausea, vomiting, dry mouth, constipation, muscle pain, bone pain, abdominal pain, polyuria, polydipsia, anorexia, weight loss, nocturia, conjunctivitis (calcific), pancreatitis, photophobia, rhinorrhea, pruritus, hyperthermia, decreased libido, elevated BUN, albuminuria, hypercholesterolemia, elevated AST/ALT, ectopic calcification, nephrocalcinosis, hypertension, cardiac arrhythmias.
Interaction :
Agents which cause rise in Serum Calcium: Use with caution.
Calcium Channel Blockers: May antagonise the effects of calcium channel blockers by increasing the serum calcium levels.
Digoxin: May be associated with digoxin toxicity by increasing calcium levels.
Corticosteroids: Decrease absorption counteracting the calcitriol function of increasing calcium absorption.
Renal Dose :
Dose in Renal Impairment GFR (mL/min)
| 20-50 | Dose as in normal renal function. Titrate to response |
| 10-20 | Dose as in normal renal function. Titrate to response |
| <10 | Dose as in normal renal function. Titrate to response |
Dose in Patients undergoing Renal Replacement Therapies
| CAPD | Unlikely to be dialysed. Dose as in normal renal function |
| HD | Not dialysed. Dose as in normal renal function |
| HDF/High flux | Not dialysed. Dose as in normal renal function |
| CAV/VVHD | Unknown dialysability. Dose as in normal renal function |
Hepatic Dose :
No dosage adjustments are recommended.