Comparison of phenytoin and phenobarbital effects on far-field auditory and somatosensory evoked potential interpeak latencies.

Far-field somatosensory and auditory evoked potential (EP) interpeak latencies were measured in normal controls, epileptics not receiving medications, and epileptics receiving phenytoin, phenobarbital, or both. Phenytoin, but no phenobarbital, was associated with a prolongation of EP interpeak latencies at serum level concentrations over 20 micrograms/ml. Neither carbamazepine nor primidone in smaller series were associated with prolongation of EP interpeak latencies.