Incidence of Anticonvulsant Osteomalacia and Effect of Vitamin D: Controlled Therapeutic Trial

The bone mineral content (B.M.C.) in both forearms (related to total body calcium) was measured by photon absorptiometry for a controlled therapeutic trial in a representative sample of epileptic outpatients, comprising 226 patients treated with one or two major anticonvulsant drugs (phenytoin, phenobarbitone, primidone). Initially the mean B.M.C. value for all epileptic patients was 87% of normal. During treatment with 2,000 international units of vitamin D2 daily for three months an average B.M.C. increase of 4% was found, whereas the B.M.C. values remained unchanged in the placebo group and in the control groups. The incidence of hypocalcaemia and raised serum alkaline phosphatase was 12% and 43% respectively. The biochemical indices of osteomalacia were related to B.M.C. These results indicate that epileptic patients should be closely supervised for the occurrence of anticonvulsant osteomalacia, and, possibly, receive prophylactic treatment with vitamin D.