Researchers have revealed that antifungal drug clotrimazole (CTZ) ‘markedly’ reduced the risk of fungal dysbiosis when treating canine otitis externa.
They suggest that the drug could be added to piperacillin-tazobactam (PT) treatment, which otherwise commonly sees cases of fungal dysbiosis such as Malassezia after treatment. Researchers say the combined treatment still maintains ‘excellent’ antibacterial effectiveness.
The study was conducted by researchers from the Royal Veterinary College, who investigated the treatment outcomes in dogs with refractory bacterial otitis externa.
To assess the efficacy of different treatment methods, researchers examined the treatment of 35 dogs. 21 of these had been treated with topical PT which was combined with an intermittent administration of one per cent CTZ, while 14 had received only PT.
Researchers assessed that the addition of CTZ had reduced the risk of fungal dysbiosis by 81 per cent, compared to PT therapy alone. The increased CTZ and associated reduced PT did not evidence any compromise to antibacterial effectiveness.
Yeast counts were increased in every dog that was treated with PT alone, but an increase was only observed in a third of the dogs that received the PT-CTZ combination.
Researchers are now recommending that clinicians consider the concurrent use of CTZ when using PT therapy to minimise the risk of secondary yeast overgrowth.
The project has formed the research component of Dr Georgina Gallow’s dermatology residency programme. Dr Gallow said: “My predecessor, Dr Jonna Juhola and team, showed that fungal dysbiosis was a common issue in dogs with chronic otitis externa treated with potent antibacterial monotherapy, mostly for refractory pseudomonad infections. It was most satisfying to extend the work and identify a solution.”
Professor Ross Bond, who supervised, added: “We are most grateful to BSAVA PetSavers for kindly agreeing to extend their original funding to enable the assessment of clotrimazole in this clinical scenario.
“Whilst dysbiosis tends not to occur in routine cases managed with conventional polypharmacy ear drop products, the results have enabled us to adopt preventative therapy to improve the outcome of the most challenging cases of otitis.”
Image © Unai Huizi Photography/Shutterstock
Companies marketing medicines for small pets exempt from authorisation must submit their annual return to the Veterinary Medicines Directorate (VMD) by 30 November 2026.
