The specificity of action of SSRIs is associated with fewer side effects than that of TCAs. Adverse effects reported in veterinary
patients with SSRIs include increased lethargy, inappetence, restlessness, insomnia, weight loss, gastrointestinal disturbances,
anxiety, and aggression. Concurrent administration of TCAs or other SSRIs is not advisable, and concurrent administration
with monoamine oxidase inhibitors or L-tryptophan is contraindicated. A minimum washout period of two to three weeks is advisable
before and after monoamine oxidase inhibitor administration.16,18
Melatonin is a naturally occurring indole amine hormone produced by the metabolism of serotonin and secreted by the pineal
gland. In both nocturnal and diurnal animals, the relative concentrations of serotonin and melatonin in the pineal gland are
inversely related within the daily photoperiod (i.e. during daylight hours, serotonin concentrations are high and melatonin concentrations are low; during nighttime hours, melatonin
concentrations are high and serotonin concentrations are low). In addition to applications for some primary dermatologic conditions,
melatonin may be effective as an anxiolytic. Melatonin has been reported to be serotonergic (possibly as a result of its derivative
and inverse relationship with serotonin) and may also function as a GABAergic agonist. Potential adverse effects of melatonin
in dogs and cats include somnolence (often transient) and diarrhea.
Vint Virga, DVM, DACVB
Behavioral Medicine for Animals
Veterinary Healing Arts, Inc.
P.O. Box 431
East Greenwich, RI 02818
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