Background: Currently available topical otic preparations contain a variety of antibiotics and other ingredients that are potentially damaging to the middle and inner ear. There is therefore a need to identify agents that are safe as well as effective for topical otologic use. In pursuit of that goal, we used an animal model to evaluate the ototoxic potential of the broad-spectrum, penicillin derivative ticarcillin--both alone and combined with clavulanic acid (a beta-lactamase inhibitor).
Methods: Twenty chinchillas served as subjects. Ten of the animals were given a single middle ear application of ticarcillin; the remaining 10 animals received ticarcillin disodium plus clavulanate potassium (Timentin). Five animals from each of the two groups were killed after 1 week to assess short-term effects and the other five animals in each group were kept for 4 weeks before their temporal bones were removed for histologic study.
Results: Significant toxic effects, involving both the middle and inner ear, were observed in all experimental groups. Alterations of the middle ear at 1 week included inflammation, hemorrhage, and effusions. Middle ear cholesteatomas were observed at 4 weeks. Inner ear changes seen at 1 and 4 weeks included hair cell loss, supporting cell degeneration, and strial damage.
Conclusion: The study results indicate that ticarcillin should not be considered for further evaluation as a possible antibiotic for use in ototopical preparations.