Study raises concerns about some compounded enrofloxacin ear mixes

A new Auburn University study presented at the 2025 North American Veterinary Dermatology Forum found that not all compounded enrofloxacin ear preparations behave the same once mixed. In the 20-day evaluation, researchers tested 12 compounded otic solutions made with either 100 mg/mL or 22.7 mg/mL enrofloxacin plus different vehicles and add-ins, including sterile water, tris-EDTA, dexamethasone, ketoconazole, and miconazole. Solutions made with sterile water remained compatible and stable, but formulations containing tris-EDTA showed marked concentration loss by day 10, and combinations containing antifungals showed immediate incompatibility, including separation, precipitation, and even an exothermic reaction that prevented drug-strength testing. (navdf2026.com)

Why it matters: Compounded enrofloxacin solutions are commonly used in canine otitis care, especially when clinicians need flexibility beyond labeled products. But this study suggests some widely used combinations may deliver less active drug than intended, or may not remain physically usable after compounding. That matters for treatment response, antimicrobial stewardship, and client communication, particularly when a pet parent is paying for a custom preparation expected to stay effective through the treatment course. Earlier work had suggested enrofloxacin could remain stable for 28 days in some ear-cleaner vehicles, and a 2023 study found enrofloxacin plus saline and dexamethasone remained stable over 28 days, underscoring that the vehicle and additives, not just the drug, drive performance. (navdf2026.com)

What to watch: Watch for a full peer-reviewed publication with complete methods and practical compounding recommendations, especially around whether tris-EDTA or antifungal combinations should be avoided altogether or only under specific formulations. (navdf2026.com)