Name: Calcitriol/1,25-(OH)2-cholecalciferol (Rocaltrol)
Class: Vitamin
Mechanism: Increases intestinal absorption of calcium and phosphate. Stimulates bone resorption by facilitating effects of PTH. Stimulates renal reabsorption of calcium and phosphate. Net result = calcium, phosphate.
Absorpt.: Oral usu ® adequate absorption. Bile essential for absorpt. Parenteral.
Dist.: Stored in fat and muscle. Tightly bound to vitamin D-binding protein.
Metabolism.:
Excretion, t½: 1° = bile. Hours.
Toxicity/S.E.s: Excess accumulation in fat/muscle, hypervitaminosis D, hypercalcemia. Drug interactions—phenytoin and phenobarbital reduce sensitivity to vit. D and/or increase rate of inactivation of calcitriol.
Utility: Vit. D Metabolism. of choice for rapid action. Raises serum calcium in 1-2 d. Treat X-linked hypophosphatemic rickets (0.25-1 mg/d + phosphate salts). Treat renal osteodystrophy 2° to chronic renal disease. Ameliorates Type I vit. D-dependent rickets (0.25-0.5 mg/d). Treat hypoparathyroidism (+ calcium).
Special Features: Does not require liver or kidney activation (fully activated).