Effects of neomycin on the waveform of auditory-evoked brain stem potentials in dogs.

Neomycin sulfate was administered intravenously to eight mixed-breed dogs at a dosage of 30 mg/kg/day for as long as 50 days. Auditory-evoked brain stem potentials (AEBP) were recorded from the dogs three times a week. The AEBP amplitudes and latencies from the eight treated and the eight control dogs were compared. All treated dogs eventually exhibited an isoelectric AEBP. The time required for the AEBP waveform loss to occur in the treated dogs varied between 22 and 50 days. The AEBP waveforms were still isoelectric when measured as long as 150 days after neomycin administration was stopped. The fact that AEBP did not return would tend to support the findings of others that the loss of the receptors in the inner ear, due to neomycin toxicity, is permanent. The results of this electrophysiologic study indicate that the organ of Corti (organum spirale) is the site of pathologic changes in the auditory system that result from neomycin treatment.