Absorption and biotransfomation of cholecalciferol in drug-induced osteomalacia

The gastrointestinal absorption of vitamin D3 and its biotransformation to 25-hydroxycholecalciferol was studied in patients with drug-induced osteomalacia. The mean coefficient of absorption was virtually identical in the drug-treated group (82.8%) and the control (83.8%). The biotransformation of vitamin D3 to 25-hydroxycholecalciferol was significantly accelerated (P less than 0.03) in the drug-treated group compared to the control group. These data suggest that vitamin D absorption is not significantly altered but that biotransformation of vitamin D3 to 25-hydroxycholecalciferol is accelerated in drug-induced osteomalacia.