Effect of topical fosfomycin on polymyxin B ototoxicity.

Fosfomycin is an antibiotic that has been found to reduce the ototoxicity of aminoglycoside antibiotics and cisplatin when systemically coadministered. Polymyxin B, an antibiotic frequently used in ototopical preparations, has been shown to be ototoxic in experimental studies. To investigate the effect of fosfomycin on polymyxin B ototoxicity, topical administration of the two agents into the middle ear cavity was performed. Two groups of chinchillas were used. One group received applications of polymyxin B alone, and the second group received polymyxin B combined with fosfomycin. It was found that application of polymyxin B produces severe damage to the cochlea. However, when polymyxin B was given in combination with fosfomycin, cochlear damage was dramatically reduced. It is likely that in clinical use, a combination of polymyxin B and fosfomycin would demonstrate reduced risk of ototoxicity.