Evaluation of the Short-Term Effects of Mirtazapine on Appetite Stimulants in Dogs: A Retrospective Study and a Placebo-Controlled Trial
by
, , , and
Stephanie S. Theodoro
1,2,*
,
Maria Eduarda G. Tozato
1,
Thais O. Ximenes
1,
Lara M. Volpe
1,
Camila Baptista da Silva
1,
Fabio A. Teixeira
3 and
Aulus C. Carciofi
1 1
Veterinary Medicine and Surgery Department, College of Agrarian and Veterinarian Sciences (FCAV), São Paulo State University–UNESP, Jaboticabal 14884-900, SP, Brazil
2
Graduate Program in Animal Production, University of Brasil, Fernandópolis 15600-000, SP, Brazil
3
School of Veterinary Medicine and Animal Science, University of São Paulo-Brazil, São Paulo 05508-270, SP, Brazil
*
Author to whom correspondence should be addressed.
Animals 2025, 15(17), 2538; https://doi.org/10.3390/ani15172538
Submission received: 1 August 2025
/
Revised: 20 August 2025
/
Accepted: 26 August 2025
/
Published: 29 August 2025
(This article belongs to the Special Issue Optimizing Pet Diets: A Nutritional Approach to Wellness)
Simple Summary
Many sick dogs lose their appetite, which makes it harder for them to recover. Feeding tubes are often the best solution, but not all pet owners agree to use them. Mirtazapine is a medicine already used in cats to help stimulate appetite, but there is limited information about its use in dogs. This study evaluated how well mirtazapine works in dogs with reduced appetites. First, the medical records of over 100 dogs were reviewed, which showed that dogs who received mirtazapine were more likely to start eating again. Then, in a controlled study with 25 dogs, those who received mirtazapine ate more food than those who received a placebo on the first day. The medicine was safe and did not cause side effects. These results suggest that mirtazapine can be a helpful and safe option to encourage eating in sick dogs when other methods are not possible, especially in the short term.
Abstract
Anorexia and hyporexia are common clinical signs in dogs with acute or chronic illnesses, often requiring targeted nutritional interventions. Mirtazapine, an orexigenic drug widely used in cats, has limited evidence supporting its use in dogs. This study evaluated mirtazapine’s efficacy as an appetite stimulant in dogs using a two-part approach: (1) a retrospective analysis of 107 clinical cases comparing dogs that received mirtazapine to untreated controls; and (2) a prospective, placebo-controlled, double-blind crossover trial involving 25 dogs. In the retrospective analysis, dogs treated with mirtazapine were significantly more likely to resume voluntary food intake (OR = 3.06) and had less weight loss compared to controls. In the prospective trial, mirtazapine significantly increased food acceptance on the first day (100% vs. 63.6%, p = 0.03), with no adverse effects observed. However, the effect was not maintained on the second day, possibly due to residual drug activity or clinical improvement. Latency to feeding averaged 120 min post-administration. Mirtazapine was safe and well tolerated, even in dogs with comorbidities. These findings support the short-term use of mirtazapine as a second-line appetite stimulant in dogs when enteral feeding is not feasible.
Keywords:
anorexia; hyporexia; orexigenic; nutrition
