Topical application of mitomycin C in combination with dexamethasone: effective delay of myringotomy closure

The object of this study was to investigate the efficacy of topical mitomycin C (MMC) in combination with subsequent topical dexamethasone to prolong the patency of myringotomies. Bilateral instrumental myringotomies were performed in 12 rats. On both sides, a solution of MMC (2 mg/ml) was applied to the intact tympanic membrane for ten minutes before myringotomy. Dexamethasone (4 mg/ml) was applied to one tympanic membrane of each animal at days 3, 6, 9 and 14. Tympanic membranes were observed weekly for a total of 9 weeks. The mean healing period was found to be 17.5 days (range 4.5-45.5 days) in the group with MMC alone, and 32 days (range 17.5-59.5 days) in the group MMC + dexamethasone. The difference was significant. A combination of topical MMC and subsequent dexamethasone did delay the healing rate of myringotomies in rat tympanic membranes longer than MMC alone.