In vivo and in vitro efficacy of florfenicol, terbinafine, and mometasone furoate topical otic solution for the treatment of canine otitis externa

Abstract

Canine otitis externa (OE) is one of the most common dermatological problems for which dog owners frequently seek veterinary care and is associated with a high rate of recurrence [1-3]. Dogs with OE may show erythema, swelling, exudate, and clinical signs related to pruritus and pain due to inflammation in the external ear canal [3,4]. Numerous underlying issues can cause or worsen OE; however, addressing pathogens such as bacteria or yeast plays an important role in the management of OE. Although various pathogens are associated with canine OE, Staphylococcus pseudintermedius, Pseudomonas aeruginosa, and Malassezia pachydermatis are the most common pathogens found in this condition [3-7]. Thus, reducing number of these infectious organisms is critical to the successful treatment of OE. For this purpose, topical and systemic antimicrobials with or without anti-inflammatory agents are used in veterinary clinics [3]. The otic solution used in this study (Neptra; Elanco, USA) includes florfenicol, terbinafine, and mometasone furoate in a single-dose regimen. This otic solution is the Food and Drug Administration−approved, veterinarian−administered treatment for canine OE, and S. pseudintermedius and M. pachydermatis show suscepThis study evaluated the efficacy of a new, single-dose otic solution combining florfenicol, terbinafine, and mometasone furoate for the treatment of canine otitis externa (OE) in vitro and in vivo. Forty-one client-owned dogs with OE were included in the study and divided into a treatment group that received the test solution and a negative control group that received a normal saline solution. On day 0, the dogs were treated either with the test or the control solution and evaluated over 30 days. Clinical efficacy was evaluated by clinical signs and cytological organism counts. In vitro antimicrobial susceptibility was evaluated by the minimum inhibitory concentration (MIC). After treatment with the test solution, clinical signs continuously decreased and cytological scores were significantly reduced. The results of MIC testing showed that the test solution was potent against the common pathogenic causes of canine OE. In this study, the most common causative pathogens were Staphylococcus pseudintermedius, Pseudomonas spp. and Malassezia pachydermatis. No issues related to safety were identified. Based on these results, this new ototopical drug can be used as first line treatment for canine OE.