The use of dextromethorphan to treat repetitive self-directed scratching, biting, or chewing in dogs with allergic dermatitis

Objective: To evaluate the efficacy of oral dextromethorphan in dogs with a repetitive behavior problem (self-licking, self-chewing, and self-biting associated with chronic allergic dermatitis). Animals: Fourteen dogs with chronic allergic dermatitis were enrolled in the study. Twelve dogs completed the study. Procedure: The dogs were treated for 2 weeks each with dextromethorphan (2 mg/kg BID) and placebo in a randomized, double blind, crossover designed study. A dermatology score, including an assessment of affected areas of the integument and the level of self-directed behavior, was generated before and following each 2-week phase of the study. Owners were required to record daily the amount of time they spent with their dog and the amount of time that the dog was observed to be engaged in any of the specified self-directed behaviors. Results: The percent of the observed time that the dogs were reported to be involved in self-directed behaviors was significantly less during the 2-week active drug treatment phase. The pruritus score component of the dermatology score also was significantly less during the active treatment phase. In addition, a dermatologist-rated global assessment was more favorable in 11 of 12 dogs following the active treatment phase. Conclusions: Dextromethorphan significantly reduces the percentage of time that allergic dogs spend self-licking, self-chewing, and self-biting. Clinical relevance: Dextromethorphan may be a useful adjunct in the management of self-directed behaviors associated with allergic dermatitis and possibly in other repetitive behaviors as well.