Reduction of the endocochlear potential by the new "loop" diuretic, bumetanide.

The effect of bumetanide upon the endocochlear potential (EP) was examined in 46 guinea pigs. The EP was reduced with dosages of 5 mg/kg or more. The maximum depression of the EP (reduction to -30 to -40 mV) was obtained at a dosage of 30 mg/kg. The recovery of the potential was incomplete at any dosage within three hours and the response pattern of the EP to bumetanide was similar to that to ethacrynic acid. The present experiments revealed that bumetanide, by weight, has a stronger ototoxic potency than the other "loop" diuretics--furosemide and ethacrynic acid. However, the diuretic effect of 1 mg bumetanide is equivalent to 40 to 60 mg furosemide or ethacrynic acid. Therefore, the relative ototoxic potency of bumetanide is much smaller suggesting that from a clinical standpoint bumetanide is much safer than the other "loop" diuretics.