Determination of ototoxicity of common otic drops using isolated cochlear outer hair cells

Objectives: Otic drops are commonly used not only for otitis externa, but also for otorrhea in the presence of tympanostomy tubes or tympanic membrane perforations. Many studies have demonstrated the ototoxicity of common otic preparations such as Cortisporin® otic drops (Monarch Pharmaceuticals, Bristol, TN). The purpose of this study was to assess the relative ototoxicity of common otic preparations by direct exposure to isolated cochlear outer hair cells (OHCs). Methods: OHCs from adult chinchilla cochlea were exposed to standard bathing solution (control), acetic acid, Acetasol HC® (Alpharma USPD Inc., Baltimore, MD), Gentacidin® (CIBA Vision Ophthalmics, Atlanta, GA), and Tobradex® (Alcon, Fort Worth, TX). The cells were observed using an inverted microscope, and the images were recorded in digital still-frame and video, and analyzed on the Image Pro-Plus 3.0 program (Media Cybernetics, Silver Spring, MD). Results and Conclusions: As measured by time to cell death and change in morphology of OHCs, acetic acid with or without hydrocortisone was most toxic to OHCs. Cortisporin was more cytotoxic than gentamicin and Tobradex.