Ethacrynic Acid, Furosemide, and Vestibular Caloric Responses

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Abstract
Ethacrynic acid and furosemide, saluretic diuretics of high potency, have been shown to be toxic to the auditory system. In the present study, it was found that the depressant effect of ethacrynic acid extends into the vestibular system. Cats, given a 20 mg/kg intravenous bolus of ethacrynic acid, exhibited a 50% greater reduction of the vestibular nystagmus response to a caloric irrigation than control animals receiving normal saline. This was true for all three major parameters of the recorded nystagmus response (degrees of slow phase displacement, frequency of beats and slow phase velocity). This effect was very rapid in onset (present at 30 seconds postinjection), and quite transient (approaching normal by 20 minutes postinjection). Furosemide did not produce the vestibular depression. Nystagmus responses observed after injection of furosemide (at 20 mg/kg) were not significantly different from those of control animals receiving normal saline. Possible mechanisms of action and therapeutic implications of the ethacrynic acid-induced vestibular depression are discussed.