A hydrocortisone aceponate spray administered alone matched a three-drug gel containing an antibiotic, an antifungal, and a steroid in treating erythemato-ceruminous otitis externa in 200 client-owned dogs enrolled in a multicentric field trial in Japan.
What the study found
In dogs with erythemato-ceruminous otitis externa and an OTIS3 score of 5 or greater, a hydrocortisone aceponate spray (Cortotic) administered daily for 7 or 14 days showed no significant difference in clinical score reduction, cytological reduction, or treatment success rates compared to a terbinafine/florfenicol/betamethasone acetate gel (Osurnia) administered on Days 0 and 7. At Day 28, the steroid-only spray showed a 72.1% reduction in OTIS3 score; the three-drug gel showed 76.1%. Treatment success rates were similar between groups at all time points, and relapse rates were low in both. Veterinarians subjectively assessed efficacy as good or excellent in 83% of cases for the steroid-only spray and 87% for the three-drug gel at Day 28. Both treatments were well-tolerated. Cytological examination confirmed the presence of bacteria and/or yeast in the enrolled population.
How the study was built
This was a multicentric, double-blinded, randomized, parallel-group field trial conducted at 10 veterinary clinics in Japan. Two hundred client-owned dogs at least 4 months old with non-parasitic otitis externa and an OTIS3 score of 5 or greater were enrolled. Cytological examination confirmed the presence of bacteria and/or yeast and the absence of parasites. Dogs with ruptured tympanic membranes, purulent exudate, otic ectoparasites, or foreign bodies were excluded. Dogs were randomly assigned to receive either the hydrocortisone aceponate spray daily for 7 or 14 days (n=100) or the three-drug gel on Days 0 and 7 (n=100). In the steroid-only group, treatment duration was determined at Day 7 based on clinical success; if the OTIS3 score remained 4 or greater, treatment was extended for an additional 7 days. All dogs in the three-drug gel group received the full two-dose regimen on Days 0 and 7. All affected ear canals were cleaned on Day 0 before treatment; no further cleaning was permitted during the study. Clinical assessments using the OTIS3 scoring system and cytological evaluations were conducted on Days 0, 7, 14, 28, and 42. The OTIS3 system evaluates erythema, edema, exudate, and ulceration on a 0-3 scale each, with scores summed to a total of 0-12. Treatment success was defined as achieving an OTIS3 score of 3 or less. The study was designed as a non-inferiority trial with a 15% margin, requiring a minimum of 85 evaluable dogs per group to achieve 90% power at a two-sided 5% significance level. This is a field trial in client-owned dogs across multiple clinics, which supports generalizability to typical practice populations, but the study was conducted only in Japan and we don't know from the source whether investigators were masked to cytological results. Cytological assessment was performed using the validated Budach and Mueller scale, a 5-point grading system evaluating bacteria, yeast, and inflammatory cells. Samples were submitted to a laboratory for semi-quantitative cytological evaluation.
The number, and its error bars
The primary endpoint was percentage change from baseline in OTIS3 score at Day 28. The hydrocortisone aceponate spray group showed a 72.1% reduction; the three-drug gel group showed a 76.1% reduction. The source states that non-inferiority was established if the lower bound of the two-sided 95% confidence interval for the treatment difference was greater than −15%, and that non-inferiority was demonstrated, but doesn't report the actual confidence interval or p-value for the primary comparison. We'd want to see baseline OTIS3 scores, the magnitude of score reduction at Day 7, and between-group comparisons at intermediate time points, none of which the source reports. The source doesn't give relapse rates numerically beyond stating they were low in both groups.
What the authors say it cannot tell you
The source doesn't state limitations explicitly. That itself is a limitation; a reader of the source alone can't assess what the investigators considered the study's boundaries. We don't get baseline OTIS3 scores, the proportion of dogs with bacterial versus yeast overgrowth, or whether cytological reduction correlated with clinical improvement. The source doesn't state whether the study was powered to detect superiority, only non-inferiority. Adverse events aren't reported beyond stating both treatments were well-tolerated. Attrition data isn't detailed and reasons for withdrawal aren't specified.
Who paid for it
The source doesn't state who funded the study or what conflicts of interest were declared. One of the products tested (Cortotic) is manufactured by Virbac, France, and the other (Osurnia) by Bussan Animal Health CO Ltd, Japan, but the source doesn't disclose whether either company sponsored the trial.
What this means for your practice
VeterinaryPracticeNow's read, not the study's. Everything in this section is our editorial interpretation for practice owners. The study does not claim any of it.
The source cites a prior investigation comparing hydrocortisone aceponate alone with a conventional multi-agent product, and this trial adds a larger sample across multiple clinics. If you stock both products, the steroid-only option now has field-trial support for first-line use in the most common presentation you see: the inflamed, waxy ear with secondary yeast or cocci overgrowth on cytology. The operational difference is daily dosing for up to two weeks versus two in-clinic administrations a week apart, so client compliance and your appointment availability both factor into which one you reach for.
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The antimicrobial-stewardship angle is real. A steroid-only product that works means one less fluoroquinolone or aminoglycoside prescription written for an infection that's secondary to inflammation, not primary. The study doesn't tell you which cases need the antibiotic and which don't; it tells you that in a population meeting the inclusion criteria, the steroid alone worked as often as the three-drug gel. Your cytology, your otoscopy, and your read of the primary cause still decide the protocol, but the evidence now supports holding the antimicrobial in the subset of cases where inflammation is driving the overgrowth and the tympanic membrane is intact.
The relapse question matters more than the late-study success rate. The source states relapse was low in both groups but doesn't report the actual rate. A product that works in most cases and holds in most of those is a first-line option; a product that works in most cases and relapses in many is a temporizing one. The full paper will tell you which this is.