Anticonvulsant effects on the memory performance of epileptics

The effects of different drugs on memory function in epileptic patients were examined. Patients had clinically normal cognitive function, above average IQs and infrequent seizures. Compared with pre-treatment evaluation, treatment with phenytoin, but not with carbamazepine or sodium valproate, resulted in impaired memory performance after three months of treatment. Switching patients previously treated with phenytoin to carbamazepine resulted in an improvement in memory performance compared with that of patients remaining on phenytoin. Switching patients from carbamazepine to sodium valproate did not result in any change in performance compared with that of those remaining on carbamazepine. The results of these experiments suggest that phenytoin, but not carbamazepine or sodium valproate, causes impaired memory performance. The nature of the memory dysfunction and its clinical implications are discussed.