Single ototopical application of mesna has no ototoxic effects on guinea pig cochlear hair cells: a morphological study.

Mesna (Mistabron) is a mucolytic substance that is also used for chemically assisted dissection during cholesteatoma surgery. The present animal study aims to evaluate its possible ototoxic side effects. To this end, the right tympanic cavity of 9 guinea pigs was filled with either 20% mesna or 10% neomycin (serving as a positive control), while the left tympanic cavity was filled with saline (serving as a negative control). One week after administration, the inner ears were dissected out and further processed for morphological evaluation by means of either interference contrast microscopy or scanning electron microscopy. No macroscopic signs of middle ear inflammation were observed in any of the ears treated. Whereas damage was obvious in all neomycin-treated specimens, the morphology of both saline- and mesna-treated inner ears was unaffected. These findings led us to conclude that, at least on a morphological basis, no indications are at hand to assume ototoxic effects of this mucolytic substance due to a single application during cholesteatoma surgery.