Auditory impairment in guinea pigs treated with isepamicin.

Groups of adult guinea pigs were treated intramuscularly with isepamicin at doses of 100, 150 and 225 mg/kg/day for 21 days. For comparison, two other groups were administered either saline or amikacin 225 mg/kg/day. Auditory function, as measured by the Preyer pinna reflex and the brain stem evoked response, was impaired in both the isepamicin and amikacin groups treated with 225 mg/kg/day, and to a lesser extent in the group receiving isepamicin 150 mg/kg/day. Morphological evaluation of the organ in Corti, performed either by scanning electron microscopy or by light microscopy, showed the typical pattern of damage associated with the aminoglycosides. The greatest damage was observed at 225 mg/kg/day, with no difference between isepamicin and amikacin. Isepamicin 100 mg/kg/day produced no impairment in auditory function and very little change in the morphology of the organ of Corti.