Abstract
Antibiotics which have ototoxicity should be carefully administered in clinical treatment. Patients with chronic otitis media are often treated by intratympanic administration therapy. Basic studies on its safety regarding ototoxicity, however, have rarely been reported.
The present study was performed to examine the influence of intratympanic antibiotic administration on the internal ear in 24 guinea pigs (12 in the gentamicin therapy group, 9 in the cefsulodin therapy group and 3 in the isonic sodium chloride therapy group as the control). Cefsulodin sodium solution of 0.2ml (20mg), gentamicin solution of 0.2ml (8mg) and isonic sodium chloride solution of 0.2ml were instilled into the tympanic cavity through a silicon tube at the back of the ear of the guinea pig for 4 days. Electrocochleography (ECoG) was performed to examine the ECoG-threshold on the experimental animals and scanning electromicroscopy (SEM) was also used to observe the exstirpate cochlea after sacrifice. Neither worsening of the audioresponses (ECoG-threshold) nor SEM findings were observed in the cefsulodin or control groups.
On the other hand, the audioresponses were reduced in the gentamicin group. A statistically significant intergroup difference between the cefsulodin and gentamicin groups in the threshold of ECoG-responses was observed. Significant structural evidence of hair-cell insult such as swelling and rupture of the cell membrane was observed in the gentamicin group.
