The goal of most canine anxiety medications is to lower the overall anxiety level so the dog can learn new responses and change behaviors. Benzodiazepines are gamma-aminobutyric acid (GABA) agonists that produce anxiolytic effects and thus are ideal when rapid administration on an as-needed basis is desirable (eg, during storms, car rides, trips to the groomer).
SSRIs block the reuptake of serotonin, making it more available in the neural synapse. Serotonin modulates mood, anxiety, satiety, cognition, aggression, and sexual drive. Agents from this drug class are commonly used in patients with separation anxiety, compulsive disorders, aggression, and phobias and would be appropriate if benzodiazepines did not improve the pet’s thunderstorm anxiety.
TCAs have a similar, although less serotonin-selective, mechanism of action as that of the SSRIs. This drug class is similarly indicated if benzodiazapene administration was not adequate to improve the pet’s thunderstorm anxiety.
Buspirone, the most common azapirone, is a partial serotonin agonist, with effects similar to those of TCAs and SSRIs. Buspirone has fewer side effects than do TCAs and SSRIs and may, therefore, be a better choice in senior patients or those with a concurrent illness.
MAOIs inhibit the enzyme that catabolizes oxidative deamination of catecholamines in the CNS and are used more commonly in dogs with cognitive dysfunction syndrome.
From: Medical Management of Behavioral Problems by Terry M. Curtis, DVM, MS, DACVB, University of Florida
From: Storm Phobias in Dogs by Debra F. Horwitz, DVM, DACVB, Veterinary Behavior Consultations, St. Louis, Missouri