Retrospective study on the use of fluvoxamine in 72 dogs with anxiety disorders

Fluvoxamine is a selective serotonin reuptake inhibitor (SSRI) and potent σ1-receptor agonist, commonly used in human medicine to treat major depressive disorders, obsessive-compulsive disorders, and other anxiety disorders. To our knowledge, its clinical use in canine behavior medicine has not been well-studied. The purpose of this retrospective study was to document the use of fluvoxamine in conjunction with behavior modification and appropriate environmental changes, in client-owned dogs diagnosed with various anxiety disorders. Our hypothesis was that fluvoxamine combined with the other recommendations could result in a positive outcome without major side effects. All dogs diagnosed with at least one anxiety disorder between January 1, 2016 and June 30, 2020 and who received at least 6 months of fluvoxamine were included (n = 72). A total of 100 dogs were diagnosed with at least one anxiety disorder and were prescribed fluvoxamine during the study period, but 28 dogs were excluded from the study as they did not take fluvoxamine for at least 6 months for various reasons (lost to follow-up, euthanasia, side effects, deterioration, insufficient effect, change of ownership, et cetera). A phone survey was conducted to validate data in the medical records of the dogs included and enquire about the perceived effect of fluvoxamine. Out of the 72 dogs with at least one anxiety disorder, 11 had an anxiety disorder without aggression, 47 were aggressive towards humans, 51 were aggressive towards other dogs, 5 had compulsive/obsessive-compulsive disorders, and 32 had suspected or confirmed separation anxiety. Of these dogs, 45% showed a marked improvement, 38% showed a moderate improvement, 15% showed a minimal improvement, 2% showed no improvement and none worsened. The presence of a concomitant treated medical condition and the optimal dosage of fluvoxamine respectively showed a positive and a negative correlation with the effect of treatment. None of the variables were significantly correlated with the time to reach the optimal dosage. 81% of dogs showed some degree of undesirable effects. The vast majority of these undesirable/side effects were considered mild, temporary and were observed during the first weeks of treatment or during periods of dose adjustments. Fluvoxamine offers a safe and promising alternative for patients who do not respond to approved SSRI or tricyclic antidepressants.