Safety of ofloxacin (OFLX) and fosfomycin sodium (FOM) ear drops

Objective: The objective of this study is to evaluate the safety of two ear drops, Ofloxacin (OFLX: Taribid Otic Solution^®, Daiichi Seiyaku) and Fosfomycin sodium (FOM: Fosmicin S^®, Meiji Seiyaku). Methods: Albino guinea pigs were used as experimental animals, and the ototoxicity was evaluated by means of threshold changes in the compound action potentials (CAP), when topically applied to the middle ear cavity of the guinea pig. The sound stimuli applied were; click sound, with tone bursts of 8 kHz, 4 kHz, and 2 kHz. In one group of animals, after one application of the ear drops in the right middle ear cavity, the change in CAP was compared with a contralateral saline control at 24 h, one week, and four weeks. In other group of animals, the ear drops were applied into the middle ear cavity for seven consecutive days and the CAP was measured at 24 h. Results: At 24 h the CAP threshold for click, 8 and 4 kHz elevated significantly for both the saline and ear drop treatment, but the threshold returned to normal when measured at 7 days and 28 days. Seven consecutive days of ear drops administration resulted in no reduction in the CAP for either ear drops. Conclusions: Based on the lack of changes in the CAP, these two ear drops studied did not show any significant ototoxicities.