Detection of ototoxicity from drugs applied topically to the middle ear space.

This paper summarizes data obtained from two separate studies done in our laboratory. Both studies were done to investigate the possibility that drugs commonly applied to the middle ear space could be the cause of sensori-neural hearing loss. The two drugs that were felt to be the most likely candidates for the studies were neomycin and polymyxin B. In the neomycin study, the various drug concentrations were administered three times a day for four weeks. In the polymyxin B study, the administration was three times a day for two weeks. Cochlear function was evaluated electrophysiologically and by examination of surface preparations of the organ Corti. The data show that both neomycin and polymyxin B can, in concentrations similar to those found in commercially available otic drops, induce cochlear damage when they are applied to the middle ear space of guinea pigs. The degree of damage produced is related. In the case of neomycin, it was shown that the effect worsens as the duration of the dosage administration is extended...