Does N-acetylcysteine Improve Established Hearing Loss in Guinea Pigs?

OBJECTIVE: To assess whether multiple injections of a powerful antioxidant can improve established sensorineural hearing loss in guinea pigs. STUDY DESIGN: Animal study. SETTING: Animal science laboratory, University of Manitoba. METHODS: A total of 16 guinea pigs were used in our study: 8 underwent unilateral intracochlear neomycin injection, and 8 underwent unilateral saline to serve as controls. After a period of 3 weeks for hearing loss to stabilize, 4 guinea pigs from each group received weekly intraperitoneal injections of N-acetylcysteine (NAC) for 4 weeks. Click auditory brainstem response (ABR) testing was conducted at baseline, weekly after the start of NAC injections, and after the last injection. Pure tone ABR tests were conducted prior to intracochlear injections and at completion of the study. RESULTS: Click ABR thresholds were significantly worse in ears treated with neomycin (P < .001), as expected, but not significantly different when treated with NAC (P = .664). Thresholds for pure tone ABR were also not statistically different in neomycin-treated ears with or without NAC (P > .99). CONCLUSIONS: The aggressive antioxidant therapy performed in this study was not successful in improving established hearing loss via an antioxidant regimen that is known to change the oxidation-reduction potential in the cochlea.