Effects of transdermal mirtazapine on hyporexic rhesus and cynomolgus macaques (Macaca mulatta and Macaca fascicularis).

Background: Hyporexia and weight loss are important indicators of physical and psychological well-being in macaque colonies. An FDA-approved transdermal formulated Mirtazapine (MTZ) shows effectiveness in managing feline hyporexia. This study sought to determine its effectiveness as an appetite stimulant in macaques.

Methods: Fourteen macaques with idiopathic hyporexia, intractable to conventional management were treated with transdermal MTZ (0.5 mg/kg) topically administered to aural pinnae once daily for 14 days. Qualitative food consumption was monitored daily for 6 months. Body weights were collected prior to treatment, every 2 weeks for the first 6 weeks, 10 weeks, and 6 months post-treatment.

Results: Transdermal MTZ significantly reduced the frequency of hyporexia during treatment and monthly for 6 months. No significant increase in weight noted until approximately 6 months post-treatment.

Conclusions: Results from this study indicate that a short course of transdermal MTZ is an effective way to increase food consumption in macaques chronically.