Treatment of canine otitis externa: a randomized, double-blinded, clinical field study comparing the hydrocortisone aceponate monotherapy to a multi-agent reference product.

Erythemato-ceruminous otitis externa (ECOE) is a canine inflammatory condition very frequently involving secondary microbial infections. This multicentric, masked, randomized, clinical field trial in Japan evaluated the efficacy and safety of a hydrocortisone aceponate (HCA) spray solution (Cortotic™, Virbac, France) compared to a terbinafine/florfenicol/betamethasone acetate ear gel (Osurnia™, Bussan Animal Health CO Ltd, Japan) in 200 dogs with ECOE (OTIS3 ≥ 5). Dogs received either Cortotic™ daily for 7 or 14 days or Osurnia™ on Days 0 and 7. OTIS3 clinical evaluation and cytological examinations were conducted, as well as the subjective veterinarian product efficacy evaluation. Results showed no significant differences between groups in OTIS3 score reduction, cytological reduction, or treatment success rates at any time point. On Day 28, Cortotic™ showed a 72.1% OTIS3 reduction, comparable to Osurnia™ 76.1%. Treatment success rates were also similar, and relapse rate was low in both groups. On Day 28, the veterinarians subjectively assessed the efficacy as good or excellent in 83% of cases for Cortotic™ and 87% for Osurnia™. Both treatments were well-tolerated. Cortotic™ demonstrated non-inferiority to Osurnia™ regarding clinical and cytological efficacy. The use of Cortotic™, a corticosteroid-monotherapy, can offer an effective strategy for managing ECOE while avoiding unnecessary antibiotic exposure. This study supports Cortotic™ as a first-line therapeutic option for otitis externa in dogs.