Carbamazepine and bone mineral metabolism

The status of bone mineral metabolism was studied in 21 epileptic out-patients receiving carbamazepine as the sole anticonvulsant drug. Hypocalcaemia was found in 3, hypophosphataemia in one and elevated serum alkaline phosphatase in 4 of the cases. Serum 25-hydroxyvitamin D values were significantly lower in the patients than in the controls. No statistically significant difference was observed in bone mineral density between the patients and controls. Histomorphometric analysis of the iliac crest cancellous bone did not reveal any statistically significant difference in the amount of trabecular bone or osteoid between the patients and controls, but the patients had an increased amount of trabecular resorption surfaces. An increased amount of osteoid, suggesting histological osteomalacia, was found in 2 of the 18 biopsies. We conclude that epileptic out-patients receiving carbamazepine therapy have vitamin D deficiency and may develop osteomalacic changes in their skeleton.