Vestibulotoxicity of Ethacrynic Acid

Temporary or permanent vestibulo‐auditory disability may develop after the administration of the diuretic, ethacrynic acid. A transient loss of hearIng is well documented in the literature; yet, it is suspected that permanent deafness requires the interaction of aminoglycoside agents, other ototoxic drugs, or at least renal failure. A review of earlier experiments shows that the drug affects sodium‐potassium relationships, the stria vascularis and possibly the viability of the organ of Corti. Since fluids and morphologic structures within the vestibular system are similar to those in the auditory system, it would be expected that ethacrynic acid would cause similar damage in both areas of the ear. This hypothesis was tested by a series of experiments designed to determine drug‐induced changes in the vestibulo‐ocular reflex of the cat. Evaluation of the data demonstrated that ethacrynic acid, in dosages at or greater than 20 mg./kg., produced an immediate depression in the cochlear response. Although larger dosages of the drug caused a more severe depression, all responses returned to normal within 30 minutes. Evaluation at two days revealed no permanent alterations. The optokinetic‐induced eye displacement and symmetry were stable, and habituation from repetitive caloric stimulations was not affected by the administration of the drug. The experiments demonstrated that ethacrynic acid was toxic to the vestibular system which again reinforced the precautions that should be taken in the administration of the diuretic to the patient. The transient nature of the vestibular depression suggested the possibility of applyIng this diuretic, or similar drugs, to the control of vestibular symptoms.