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.

Adenosine agonists CGS 21680 and NECA inhibit the initiation of cocaine self-administration.

Administration of the adenosine antagonist caffeine will facilitate the reinstatement of cocaine self-administration responding. This suggests that adenosine receptors may play a role in the motivational systems that regulate cocaine-seeking behaviors. If so then adenosine agonists may act to block cocaine self-administration. To test this hypothesis, the effects of the nonselective adenosine agonist NECA and of the A2A selective agonist, CGS 21680 on the self-administration of cocaine were determined. In these experiments, rats were allowed to obtain intravenous cocaine infusions (0.6 mg/kg/infusion) delivered under a Fixed Ratio 5 schedule. Treatment with either NECA or CGS 21680 in comparison to vehicle administration reduced the number of infusions received per session. This, primarily, was due to a marked increase in the latency for delivery of the first cocaine infusion. Responding after drug-induced delays tended to be at control levels. Adenosine agonists are known to have sedative effects and these actions might play a role in NECA and CGS 21680-induced increases in latencies for cocaine delivery. These results indicate that the administration of adenosine agonists may inhibit cocaine-seeking behaviors. The degree to which these actions are on motivational systems as opposed to involving less specific effects remains to be fully elucidated.