Effects of edaravone treatment on noise-induced hearing loss

This study investigated the effects of edaravone on the cochlear hair cells of guinea pigs after noise-induced hearing loss and the best time for drug administration. Thirty clean-grade guinea pigs were randomly divided into three groups, and auditory brainstem responses (ABRs) were measured before, instantly after, and on the 3rd and 7th day after noise exposure. On the 8th day after noise exposure, succinate dehydrogenase immunohistochemistry and scanning electron microscopy (SEM) were performed. The ABR threshold of the group that was administered edaravone immediately after the noise exposure was lower compared with that of the saline group (P<0.05). Three days later, the ABR threshold in the group was decreased more. Seven days later, it was similar to the ABR of the normal control group, while the ABR of the saline group was significantly higher than that of the normal control group (P<0.05). Light microscopy revealed that the cytoplasm of the outer hair cells was more intensely stained in the edaravone group compared to the saline group. The cellular morphology, immunohistochemistry, and SEM analyses showed that the edaravone group exhibited significantly less nuclei and cilia deficits than the saline group did. The early intraperitoneal injection of edaravone had beneficial effects on the cochlear hair cells of guinea pigs after noise exposure injury. Edaravone was effective when administered within 1 week of the noise exposure, but it was most effective when it was administered within 3 days of the noise exposure.