Influence of Maropitant Citrate on Pollen and Control Intradermal Test Reactivity in Atopic Dogs: A Randomised,...

Maropitant citrate (Cerenia; Zoetis) is a neurokinin-1 receptor antagonist that inhibits binding of substance P, and is approved to prevent acute emesis and motion sickness in dogs. Maropitant is often administered before sedation with α2-agonists to reduce the risk of vomiting. Many medications interfere with intradermal test (IDT) results and it is unknown if maropitant citrate alters IDT reactivity.

To assess the influence of maropitant citrate on IDT reactivity in dogs with canine atopic dermatitis (cAD).

Twenty client-owned dogs with cAD were enrolled in a randomised, controlled, blinded, comparative trial. Each IDT was read independently by a dermatology resident and a referral clinician. Subjective (0-4) and objective (mm diameter) wheal scores were measured 15 min after intradermal injections. Four positive pollen allergens with established irritancy threshold concentrations (ITC) were selected for assessment in the next phase. Following completion of the initial IDT, maropitant citrate (1 mg/kg) was administered intravenously. A second, randomised, blinded IDT was performed using the four positive allergens injected in triplicate, with controls injected in duplicate.

Histamine (objective mean difference [MD] = 1.1 mm, p = 0.01) and positive allergen (objective MD = 0.4 mm, p = 0.007; subjective MD = 0.2 mm, p < 0.001) wheal sizes were statistically larger post-maropitant citrate. The proportions of positive allergen scores were not significantly different pre- and post-maropitant citrate (objective: 48 of 80 pre- vs. 56 of 80 post-, p = 0.09; subjective: 80 of 80 pre- vs. 77 of 80 post-, p = 0.25). No adverse events were observed.

Intravascular maropitant citrate increases wheal size, yet the effect on allergen selection for clinical treatment remains equivocal.