Effect of aminoglycoside otic drops on isolated cochlear outer hair cells with and without liver extract activation

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).

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.

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).

This study suggests that the cytotoxicity of aminoglycoside ear drops to isolated OHCs in vitro requires