Pattern of cochlear damage caused by short-term kanamycin application using the round window microcatheter method.

CONCLUSION

Short-term local application of kanamycin by the microcatheter method can control the region and severity of drug effect on the cochlea by changing the concentration and administration time.

OBJECTIVES

To investigate the effect of short-term round window administration of kanamycin by the microcatheter method on cochlear stereociliary bundle loss in a guinea pig model.

MATERIALS AND METHODS

Two concentrations and two time periods were used for drug administration to the inner ear. In groups of six animals, a total dose of 172.5 mg/ml or 345 mg/ml of kanamycin was instilled at the rate of 0.1 ml/h into the round window niche over either a 1 h or 2 h period by the microcatheter method. One group of six animals received a saline infusion as a control. The animals were sacrificed after 4 days and stereociliary bundle loss was observed by SEM. Functional changes were evaluated by auditory brainstem response.

RESULTS

With regard to the severity of the damage, higher drug concentrations were associated with more severe effects. The severity of damage was the same when the same total dose was used; however, it was found that when the dose was administered over a longer period, the damage region was wider. The functional changes also corresponded with the morphological changes.