Effectiveness of an Otic Product Containing Miconazole, Polymyxin B and Prednisolone in the Treatment of Canine Otitis Externa: Multi-site Field Trial in the US and Canada

To evaluate the effectiveness of an otic suspension containing polymyxin B, miconazole, and prednisolone (Surolan® otic suspension) in the treatment of canine otitis externa, clinical cases were recruited from veterinary practices at four geographic sites in the United States and Canada, and randomly assigned to either the test product or a positive control product containing gentamicin, clotrimazole, and betamethasone. Before and after treatment, cases were scored on four clinical parameters pain/ discomfort, erythema, swelling, and exudates. Ear swabs were taken for bacterial and yeast culture and susceptibility testing. The vast majority of all otitis externa cases in this study exhibited clinical improvement of the inflammatory signs in the ear, with 97% of cases given the test product and 95% of the cases treated with the positive control product improving clinically. Noninferiority of the test product compared to the positive control product in the treatment of canine otitis externa was shown for each of the four clinical parameters and for the total clinical score. The most frequently cultured pathogenic organisms were Grampositives, with 56% of dogs harboring isolates identified as Staphylococcus spp, 17% Streptococcus spp, 44% infections with the yeast M. pachydermatis and 12.5 % cases infected with the Gram-negative Pseudomonas spp. Susceptibility testing demonstrated a high susceptibility of all these microorganisms to the active constituents of the test product. Results show that the combination of polymyxin, miconazole, and prednisolone is a good choice for first line treatment of otitis externa in dogs.