anticonvulsant therapy-induced alterations in calcium homeostasis

35 epileptic patients, aged 10 to 58 years (mean 23), who were taking anticonvulsant drugs were studied. the patients exhibited a 34% reduction in serum calcium levels, a 41 % increase in serum alkaline phosphatase activity and a slight but insignificant decrease in serum phosphate, compared to untreated controls. these changes appear to be related to the anticonvulsant drug taken, in the following order of decreasing importance: phenytoin + phenobarbital + carbamazepine phenytoin + phenobarbital phenytoin + carbamazepine,and phenobarbital + carbamazepine. it is possible that anticonvulsant drugs alter vitamin d metabolism which results in disturbance of calcium homeostasis. moreover these changes in serum calcium and alkaline phosphatase activity in anticonvulsant treatment patients are similar to those in patients with osteomalacia.