Ototoxicity of aluminum acetate/benzethonium chloride otic solution in the chinchilla animal model.

OBJECTIVES/HYPOTHESIS To determine the ototoxic potential of aluminum acetate (0.5%)/benzethonium chloride (0.03%) otic solution in the chinchilla animal model. STUDY DESIGN A randomized, prospective, controlled study was conducted in the chinchilla animal model. METHODS Fourteen female chinchillas were used. After an incision was made in each tympanic membrane, baseline auditory brainstem response measurements were performed at 16, 20, and 25 kHz. One ear was randomized to receive aluminum acetate (0.5%)/benzethonium chloride (0.03%), whereas the other ear served as the control and received 0.9% NaCl. Solutions were applied transtympanically once a day for 3 consecutive days. Postapplication auditory brainstem response measurements were done at day 7 and day 30. In half of the animals, scanning electron microscopy was done following the last auditory brainstem response measurement. RESULTS A statistically significant difference was found between the mean threshold shifts in the experimental and control ears at all frequencies on both 7 and 30 days postapplication (P < .02). Increased ossification of the cochleae was seen in experimental ears (n = 12). Scanning electron microscopy study demonstrated outer hair cell damage and/or loss in the experimental ears. No significant morphological changes were detected on scanning electron microscopy obtained from the control ears. CONCLUSIONS Application of aluminum acetate (0.5%)/benzethonium chloride (0.03%) otic solution causes hearing loss in chinchillas when a tympanic membrane perforation exists. Further studies are needed to test the effect of this otic solution on hearing. LEVEL OF EVIDENCE 4.