Pilot evaluation of the antipruritic efficacy of a topical transient receptor potential melastatin subfamily 8 (TRPM8) agonist in dogs with atopic dermatitis and pedal pruritus.

Abstract

BACKGROUND: Atopic dermatitis (AD) requires a multimodal therapy and there is a need for effective adjunctive interventions. TRPM8 agonists are known to alleviate pruritus by inducing cooling. OBJECTIVES: To evaluate the efficacy of a novel TRPM8 agonist, 1-diisopropylphosphorylheptane (Cryosim-1), in atopic dogs. ANIMALS: Nine client owned dogs with moderate to severe pedal pruritus associated with nonseasonal AD. METHODS: This was a prospective, randomized, double-blinded, intraindividual, placebo-controlled study. A 2% Cryosim-1 or placebo-vehicle cream was applied to each forepaw twice daily for seven days. The owner rated the pruritus manifestations once daily using a pedal Pruritus Visual Analog Scale (PVAS) and provided a Owner's Global Assessment of Treatment Efficacy (OGATE) at study end. RESULTS: After seven days, the numbers of dogs with a pedal PVAS <2.0 for Cryosim-1 and placebo were three and five of nine, respectively; likewise, OGATE scores of good-to-excellent were two and five of eight, respectively - these proportions were not significant between treatment groups (P = 0.32 and 0.16, respectively). Furthermore, there was no significant difference between Cryosim-1 and placebo in the median percentage change from baseline PVAS (47% versus 75%; P = 0.15) and in the number of dogs with a &#x2265;50% or a &#x2265;90% reduction from baseline pedal PVAS (four of nine versus five of nine, P = 0.50; two of nine versus two of nine, P = 0.72). CONCLUSIONS: In this pilot trial with a TRPM8 agonist in atopic dogs with pedal pruritus, the twice daily application of a 2% Cryosim-1 cream did not have an antipruritic effect superior to that of its vehicle.