Aim: A double-blind, randomised clinical trial was conducted in Queensland general practices to evaluate the efficacy of oral doses of trimethoprim-sulfamethoxazole (cotrimoxazole) as an adjunct to Kenacomb ointment in the treatment of acute diffuse otitis externa.
Method: One hundred and five patients with otitis externa agreed to enter the trial; 13 of these had bilateral otitis externa. Six symptoms and signs of otitis externa were rated on a scale of 1 (none) to 5 (severe) and then the scores were averaged to give an index of severity. Swabs from all infected ears were cultured and then the patients were treated with Kenacomb ointment. Patients were randomly assigned to take a five-day course of either oral cotrimoxazole or an oral placebo and were reassessed on Days 2-4 and Days 5-6 after presentation.
Results: The mean duration (+/- standard deviation) of ear pain from the first visit for the cotrimoxazole and placebo groups was 3.1 (+/- 1.5) days and 3.1 (+/- 1.7) days respectively. The mean severity indices (+/- standard deviation) for these groups on presentation were 2.33 (+/- 0.59) and 2.37 (+/- 0.57). The respective reductions in these scores by the second visit were 0.72 and 0.69 and by the third visit 1.10 and 1.05. The principle pathogen isolated was Pseudomonas aeruginosa.
Conclusion: This suggests that oral cotrimoxazole is unlikely to be useful as an adjunct to Kenacomb ointment in the treatment of mild to moderate otitis externa.