Ototoxicity of kanamycin sulfate and the barriers in the inner ear.

The effect of kanamycin sulfate administered by three routes on the function of the stria vascularis was monitored electrophysiologically in guinea pigs. The three routes were intramuscular injection, perilymphatic perfusion, or endolymphatic perfusion. Neither systemic administration of 500 mg/kg of body weight per day for 7 to 12 days nor perilymphatic perfusion of 10(-3) M kanamycin affected the endocochlear dc potential (EP). However, with perfusion of kanamycin 10(-3) M in the endolymphatic space, the EP declined severely. Moreover, the decline in the EP was greater with higher concentrations of kanamycin in the endolymphatic perfusate. Furosemide given by each of the three routes produced an approximately equal decrease in the EP. The effects of kanamycin on the cells of the stria vascularis and the evidence for the perilymphatic-endolymphatic and blood-cochlear barriers are discussed.