Ethacrynic acid effect on the composition of cochlear fluids

Area of Science:

• Ototoxicity and Inner Ear Physiology
• Pharmacology of Diuretics

Background:

• Ethacrynic acid is a potent diuretic.
• Inner ear fluid composition is critical for auditory and vestibular function.

Purpose of the Study:

• To investigate the effects of ethacrynic acid on the ionic composition of inner ear fluids in vivo.
• To determine if ethacrynic acid impacts endolymph and perilymph sodium and potassium concentrations.

Main Methods:

• Administration of ethacrynic acid to six canine subjects.
• Measurement of potassium and sodium concentrations in endolymph and perilymph.
• Comparison of pre- and post-administration fluid compositions.

Main Results:

• A significant decrease in endolymph potassium concentration (145 to 21 mEq/L).
• A significant increase in endolymph sodium concentration (5.9 to 146 mEq/L).
• No significant changes observed in perilymph composition; both fluids remained slightly hypertonic to plasma.

Conclusions:

• Ethacrynic acid markedly alters endolymph ionic balance, specifically affecting potassium and sodium levels.
• The perilymphatic space appears protected from the direct ionic shifts induced by ethacrynic acid.
• These findings highlight the ototoxic potential of ethacrynic acid through disruption of inner ear fluid homeostasis.