Behavioural changes in dogs with acral lick dermatitis during a 2 month extension phase of fluoxetine treatment

Abstract

Acral lick dermatitis (ALD) is a condition described in dogs that is believed to be an animal model of obsessive–compulsive disorder (OCD) in humans. In both conditions, serotonergic neural dysfunction is believed to be responsible for aberrant grooming behaviour. ALD is the first animal model proposed for a psychiatric condition. Serotonergic antidepressants are recommended as first line treatment in OCD. However, many patients have been discouraged from using these by reports of aggression and suicide-inducing effects of these drugs. This study examined behavioural effects of a 2 month extension phase of fluoxetine treatment in dogs previously diagnosed with ALD. A 2 month extension phase on fluoxetine 20 mg daily, immediately followed on a 6 week double blind, randomised, placebo-controlled trial of fluoxetine in 63 dogs with ALD, diagnosed for at least 6 months. The Dodman scales measured excitability, fearfulness, dominance and territorial aggression at the start and end of the 2 month extension phase. Excitability was rated in four settings, referred to as questions 1 to 4. Fifty-four dogs completed the extension phase. Three subjects were withdrawn with no reason given, one for vomiting on fluoxetine. At the end of the extension phase, the analysis of variance showed no significant difference between dogs who received placebo or fluoxetine during the original trial, for scores of fearfulness (p=0·127), dominance (p=0·274) or territorial aggression (p=0·172). Excitability also caused no significant difference on the four questions (p1=0·822, p2=0·607, p3=0·975, p4=0·820). After the extension phase, owners assessed dogs as being neither more aggressive nor anxious. Particularly, there was no difference in levels of dominance aggression (p=1). Using the paired t-test there was no statistically significant difference between scores obtained both at the end of the 6 week trial and the extension phase for fearfulness (p=0·128), dominance aggression (p=1·0), territorial aggression (p=0·422) and excitability (p1=0·487, p2=0·571, p3=0·711, p4=0·086). These results may serve to refute further the reports of the emergence of impulsive aggression in human subjects on fluoxetine treatment as no significant behavioural changes were noted in the dogs treated with fluoxetine for ALD. © 1998 John Wiley & Sons, Ltd.