Acute and chronic effects of carbamazepine, phenytoin, valproate and vinpocetine on BAEP parameters and threshold in the guinea pig

ObjectiveTo characterize the acute and chronic effects of the antiepileptic drugs (AEDs): carbamazepine (CBZ), phenytoin (PHT), valproic acid (VPA) and vinpocetine (VPC), at doses 20, 6, 30 and 2 mg/kg, respectively, on the latencies and amplitudes of the waves of brainstem auditory evoked potentials (BAEPs) elicited by a supra-threshold stimulus alongside BAEP threshold.MethodsBAEPs elicited by a stimulus of high (100 dB nHL) intensity and BAEP thresholds were obtained at 4 and 8 kHz: before, after the start of treatment, and following 28 days of a daily injection of the AEDs.ResultsAfter the start of treatment BAEPs were unchanged. After the long term treatment, CBZ and PHT increased P3 and P4 wave peak latencies and reduced P4 amplitude. Chronic VPA did not modify BAEP waves, and chronic VPC reduced P3 and P4 latencies. P1 and P2 were unchanged. BAEP thresholds at 4 and 8 kHz were increased by CBZ, PHT and VPA, and decreased by VPC.ConclusionsThe chronic administration of several AEDs modifies BAEP waves of retro-cochlear origin.SignificanceAlterations in the generators of the later waves of BAEPs underlie, in most cases, the changes in hearing sensitivity produced by the long term treatment with AEDs at therapeutic relevant doses.