Ethacrynic Acid Ototoxicity Potentiation by Kanamycin

The ototoxicity of ethacrynic acid and kanamycin in combination has been investigated during acute and chronic conditions of exposure. The effect of the combination of 10 mg/kg of ethacrynic acid and 100 mg/kg of kanamycin during both exposure conditions is manifested by a significantly greater drop in measured potentials than is present in the combination with lower doses of kanamycin (50 mg/kg). This effect is manifested mainly by changes in EP. The action of ethacrynic acid and kanamycin, therefore, appears to affect primarily the metabolism of the stria vascularis. According to our electrophysiological findings during acute conditions, not only simultaneous drug exposure can increase the ototoxic effect, but sequential exposure also seems to create a treatment hazard if ethacrynic acid is given following prior exposure to an ototoxic antibiotic. Therefore, a careful evaluation of the drug history in every patient should be carried out before using ethacrynic acid for treatment.