Comparative ototoxicity of chloramphenicol and kanamycin with ethacrynic acid.

Chloramphenicol is not ototoxic if administered for systemic effect, but topical applications of it to the middle ear produce severe cochlear toxic effects. Ethacrynic acid potentiates the ototoxicity of aminoglycosides. Guinea pigs were administered chloramphenicol or kanamycin sulfate with ethacrynic acid to compare the ototoxicity of chloramphenicol and ethacrynic acid with the ototoxicity of kanamycin and ethacrynic acid. Preyer's reflex audiometry and measurement of the endocochlear dc potential, the cochlear microphonics, and the negative potential of the organ of Corti indicate that ethacrynic acid does not potentiate the ototoxicity of chloramphenicol. There is not even indirect evidence that the blood-cochlear barrier for chloramphenicol is altered by ethacrynic acid. Assuming that the ototoxicity of chloramphenicol and ethacrynic acid are similar for man and guinea pig, the combination of the administration of chloramphenicol and ethacrynic acid of systemic effect in dosages commonly used clinically should not produce greater ototoxicity than either agent administered alone.