Comparative study by scanning electron microscopy on vestibular toxicities of dibekacin, ribostamycin, and other aminoglycoside antibiotics in guinea pigs.

The vestibular toxicities of dibekacin, ribostamycin, gentamicin, and streptomycin were compared in guinea pigs. The animals were given the drugs for 21 days, examined for functional disturbances by electronystagmography (ENG), and then killed to observe morphologic changes in the vestibular sensory hairs on scanning electron microscopy (SEM). The degree of functional impairment was rated according to the duration of the postrotatory nystagmus and classified into three categories: normal, slight impairment, and severe impairment. The results of the SEM examination were similarly classified into three categories by severity of the degenerative changes in the vestibular sensory hairs, i. e., bending, fusion, ballooning, giant hair formation, or disappearance. Under these experimental conditions, the results of ENG and SEM observations showed good correlation and indicated that the vestibular toxicity was highest in the streptomycin-treated animals and lowest in the dibekacin- or ribostamycin-treated animals.