Ototoxicity of the Ethacrynic Acid

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Abstract
Ototoxicity of ethacrynic acid in concentrations of 10, 30, and 50 mg/kg was investigated by measuring the endocochlear potentials (EP), cochlear microphonics (CM), whole nerve action potentials (AP), and summation potentials (SP). Results indicated an ototoxic effect of ethacrynic acid in concentrations of 30 and 50 mg/kg, and in concentrations of 10 mg/kg if the doses were repeated in two hours. Ethacrynic acid inhibits active ion transport in the tissues of the cochlear duct. This is manifested by a drop in EP, CM, and AP. The strongest effect of ethacrynic acid was observed in the hair cells, with the drop in CM remaining after four hours with no tendency to recover. The hair cells may have a different type of metabolism from the other structures in the cochlear duct. Also, the SP appears to be comprised of two distinct parts, positive and negative, which may be generated by different sources. The negative SP is dependent on active ion transport and is altered by high dosages of ethacrynic acid.