Histological evaluation of ototoxic reaction due to some aminoglycoside antibiotics.

Twenty-one days s.c. treatment with netilmicin, gentamicin, sisomicin, and kanamicin at different doses were performed in albino guinea pigs of both sexes. Block surface preparation of Corti's organ was carried out and missing OHCs and IHCs counted in selected areas of each turn. The animals treated with gentamicin and sisomicin showed a dose-depending missing of hair cells, preferably relative to the outer ones and quantitatively the same for both the antibiotics. Furthermore, a characteristic distribution of the damage progressively increasing from the apex to the basal turn of the cochlea was detected. Kanamicin at 267 and 400 mg/kg gave the complete destruction of OHCs and IHCs along the whole cochlea while at 178 mg/kg did not show any significant damage in comparison to the control group. Finally, netilmicin neither damaged Corti's organ nor statistically determined missing OHCs and IHCs at all the doses used. These histological results and the previous electrophysiological and reflexological observations obtained in the guinea pig show a higher safety of netilmicin in comparison to the other aminoglycosides used for the problem relative to ototoxicity.