[In vivo-efficacy of an ear medication using gelatin powder as a vehicle for the therapy of canine otitis externa]. / In-vivo-Wirksamkeit eines Ohrmedikaments mit Gelatinepulver als Wirkstoffträger bei der Therapie kaniner Otitis externa.

OBJECTIVE: Otitis externa is normally treated with daily topical medication. Longer application intervals may be useful to facilitate therapy. In this study, the in vivo efficacy of a gel preparation containing marbofloxacin, dexamethasone and enilconazole was compared to that of a commercial otologic agent containing marbofloxacin, dexamethasone and clotrimazole based on clinical signs, ear cytology and bacterial/fungal cultures. MATERIAL AND METHODS: A gel preparation (group A) or a registered otologic agent (group B), respectively, was applied to 41 dogs. A total of 50 ears (25 per group) were analysed. The gel preparation was administered on days 0 and 5; the combination preparation was administered daily according to the manufacturer's recommendations. Dogs were reevaluated clinically and cytologically after 5 and 10 days. Initially and after 10 days, ear swabs were taken for bacterial and fungal cultures. RESULTS: No significant clinical or cytological differences were found between the groups. Significantly more isolates resistant to marbofloxacin were identified in group A after 10 days, although >98% of marbofloxacin was still detectable in vitro after 15 days. CONCLUSION: The clinical and cytological efficacy of a gel containing defined active agents applied twice 5 days apart was comparable to that of an authorised otologic agent applied once daily. There appears to be an increased risk with the gel in that a resistance to fluoroquinolones develops. Local adverse effects are also possible. CLINICAL RELEVANCE: A gelatine preparation containing active agents may be an alternative to daily topical therapy of canine otitis externa. The development of resistances is possible.