Treatment of chronic suppurative otitis media with topical tobramycin and dexamethasone

Objectives: 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 st eroid for the treatment of CSOM. Design: Blinded, randomized, placebo-controlled trial. Subjects: 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). Interventions: Chronic suppurative otitis media was established by inoculat ing the right ear with Pseudomonas aeruginosa. After 4 weeks of drainage, a nimals were treated according to the group assignment with 3 drops twice da ily for 7 weeks. Hearing thresholds were monitored with repeated auditory b rainstem response testing (ABR), and clinical response was monitored with r epeated otoscopic examinations and cultures throughout the study. Cytocochl eograms were evaluated for quantification of outer hair cell loss. Results: Rapid resolution of otorrhea and eradication of P aeruginosa occur red in all groups receiving tobramycin. The inclusion of dexamethasone acce lerated 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 d rug administration. Perilymph samples collected at the end of the study sho wed no detectable tobramycin. Conclusions: Combined tobramycin-dexamethasone ear drops were safe and effe ctive in the monkey CSOM model. Dexamethasone enhanced the efficacy of tobr amycin.