Neurokinin‐1 receptor antagonist (maropitant) for treatment of chronic idiopathic rhinitis in dogs: a pilot study

OBJECTIVES: Chronic idiopathic rhinitis is a common canine nasal disease with unknown aetiology and poor response to treatment. Neurokinin-1 receptor activation has been associated with rhinitis in experimental animals. The aim of this pilot study was to compare the effects of oral neurokinin-1 receptor antagonist (maropitant) with placebo on clinical signs of chronic idiopathic rhinitis in dogs. MATERIALS AND METHODS: Prospective randomised placebo-controlled double-blinded pilot trial. Eighteen privately owned dogs diagnosed with chronic idiopathic rhinitis based on clinical presentation, CT, rhinoscopy and histopathological findings were randomised to receive either maropitant 2 mg/kg (n = 9) or placebo (n = 9) orally, every other day for 4 weeks. Disease severity was assessed using study-specific scoring systems for CT and histopathological findings and derived from a validated questionnaire for nasal and gastrointestinal clinical signs. Each score was compared between groups at baseline. Response to treatment was assessed weekly by comparing the nasal and gastrointestinal scores between groups. RESULTS: Severity scores were similar between groups at baseline. Nasal scores did not differ significantly between treatment and placebo groups at the end of the trial [week 4; difference in least square means: -0.59, 95% CI -2.9 to 1.7]. The treatment group's mean score was 5.7 (range 1 to 11) at week 0 and 4.9 (range 0 to 12) at week 4, with no statistically significant change (least square means: -0.9, 95% CI -2.6 to 0.74). CLINICAL SIGNIFICANCE: Alternate-day oral administration of maropitant 2 mg/kg in dogs with chronic idiopathic rhinitis did not result in a clinically relevant reduction in clinical signs.