Treatment of chronic suppurative otitis media with topical tobramycin and dexamethasone

To investigate the safety and efficacy of a topical combination of tobramycin and dexamethasone in a primate model of chronic suppurative otitis media (CSOM) and to explore the contribution of the added topical steroid for the treatment of CSOM.

Blinded, randomized, placebo-controlled trial.

Sixty juvenile cynomolgus monkeys randomized into the following 6 treatment groups of 10 monkeys each: 0.3% tobramycin (group 1), combined 0.3% tobramycin-0.1% dexamethasone (group 2), combined 1.0% tobramycin-0.33% dexamethasone (group 3), 0.1% dexamethasone (group 4), vehicle (group 5), and phosphate-buffered saline solution (group 6).

Chronic suppurative otitis media was established by inoculating the right ear with Pseudomonas aeruginosa. After 4 weeks of drainage, animals were treated according to the group assignment with 3 drops twice daily for 7 weeks. Hearing thresholds were monitored with repeated auditory brainstem response testing (ABR), and clinical response was monitored with repeated otoscopic examinations and cultures throughout the study. Cytocochleograms were evaluated for quantification of outer hair cell loss.

Rapid resolution of otorrhea and eradication of P aeruginosa occurred in all groups receiving tobramycin. The inclusion of dexamethasone accelerated the resolution of otorrhea and negative yields of cultures compared with tobramycin alone. Otorrhea and positive culture findings persisted in the groups not treated with topical antibiotic. Results of ABRs at 4 and 8 weeks and cytocochleograms for outer cell hair loss were not affected by drug administration. Perilymph samples collected at the end of the study showed no detectable tobramycin.

Combined tobramycin-dexamethasone ear drops were safe and effective in the monkey CSOM model. Dexamethasone enhanced the efficacy of tobramycin.