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Objective --To assess the ototoxicity of commercially available Gentacidin® and TobraDex® ear drops with and without liver extract activation using isolated cochlear outer hair cells (OHCs). Material and Methods --OHCs from adult chinchilla cochleae were exposed to standard bathing solution (SBS), liver extract alone and Gentacidin and TobraDex ear drops with and without liver extract. All experiments were performed at an osmolality of 305±5 mOsm, at room temperature and for up to 60 min. OHC images were recorded using an inverted microscope and analyzed electronically. Time to cell death and changes in cell length were measured. Results --The time to cell death and the percent change in cell length were significantly shorter in the Gentacidin+liver extract group than in the Gentacidin alone group ( p <0.05). The TobraDex+liver extract group showed a significantly decreased time to cell death compared to the SBS control group ( p <0.05). There were no significant differences in cell length or time to cell death between the TobraDex+liver extract group and the TobraDex alone group ( p >0.05). Conclusion --This study suggests that the cytotoxicity of aminoglycoside ear drops to isolated OHCs in vitro requires activation. [ABSTRACT FROM AUTHOR]

Otic drops are commonly used not only for otitis externa but also for otorrhea in the presence of tympanostomy tube or tympanic membrane perforation. Many studies have demonstrated the ototoxicity of common otic preparations such as Cortisporin® otic drops. Recent studies have suggested the use of fluoroquinolone antibiotic drops as an alternative owing to their excellent antimicrobial coverage and no ototoxic effect. The purpose of this study was to assess the relative ototoxicity of four common otic preparations by direct exposure to isolated cochlear outer hair cells (OHCs). OHCs from adult chinchilla cochlea were exposed to standard bathing solution (control), Cortisporin, Cipro HC®, Ciloxan®, and Floxin®. The cells were observed using an inverted microscope, and the images recorded in digital still-frame and video, and analyzed on the Image Pro-Plus® 3.0 program. As measured by time to cell death and change in morphology of OHCs, Cortisporin was most toxic to OHCs. Among the fluoroquinolone drops, Floxin was more toxic than Ciloxan or Cipro HC. [ABSTRACT FROM AUTHOR]