- Uses/Sources: Used for the prevention and treatment of rickets or osteomalacia, and to manage hypocalcemia associated with hypoparathyroidism or pseudohypoparathyroidism. Also used for the treatment of vitamin D dependent rickets, rickets or osteomalacia secondary to long-term high dose anticonvulsant therapy, early renal osteodystrophy, osteoporosis (in conjunction with calcium), and hypophosphatemia associated with Fanconi syndrome (with treatment of acidosis).
- Symptoms: Toxicity associated with dihydrotachysterol is similar to that seen with large doses of vitamin D.
- Treatment: Treatment of overdosage consists of withdrawal of dihydrotachysterol, bed rest, liberal intake of fluids, a low-calcium diet, and administration of a laxative. Hypercalcemic crisis with dehydration, stupor, coma, and azotemia requires more vigorous treatment. The first step should be hydration of the patient. Intravenous saline may quickly and significantly increase urinary calcium excretion. A loop diurectic (furosemide or ethacrynic acid) may be given with the saline infusion to further increase renal calcium excretion. Other reported therapeutic measures include dialysis or the administration of citrates, sulfates, phosphates, corticosteroids, EDTA (ethylenediaminetetraacetic acids), and mithramycin via appropriate regimens. (L1712)
- Route of Exposure: Oral
Mechanism of Action
|Target Name||Mechanism of Action||References|
|Vitamin D3 receptor||Once hydroxylated to 25-hydroxydihydrotachysterol, the modified drug binds to the vitamin D receptor. The bound form of the vitamin D receptor serves a transcriptional regulator of bone matrix proteins, inducing the expression of osteocalcin and suppressing synthesis of type I collagen. Vitamin D (when bound to the vitamin D receptor) also stimulates the expression of a number of proteins involved in transporting calcium from the lumen of the intestine, across the epithelial cells and into blood. This stimulates intestinal calcium absorption and increases renal phosphate excretion. These are functions that are normally carried out by the parathyroid hormone.||