Comparison of the effects of lamotrigine and phenytoin on the EEG power spectrum and cortical and brainstem-evoked responses of normal human volunteers.

Phenytoin and lamotrigine (a new antiepileptic drug with an animal experimental profile resembling phenytoin) have closely similar effects on the quantitative pharmaco-electroencephalogram. These characteristics do not provide a basis for the functional classification of antiepileptic drugs nor for prediction of clinical efficacy, but they do give some insight into the probable secondary psychotropic effects which may arise with use of these drugs. Central conduction in cortical (visual) and brainstem (auditory) event-related potentials are not influenced by either drug, but peripheral nerve conduction is delayed with the use of phenytoin as reflected in increased latency wave I in the brainstem auditory-evoked response. The evidence suggests that in equivalent therapeutic dosage, lamotrigine may be less neurotoxic than phenytoin.