Journal watch13 January 2026
Author(s): S.S. Theodoro, M.E.G Tozato, T.O. Ximenes, L.M. Volpe, C. Baptista da Silva, F.A. Teixeira, F.A. and A.C. Carciofi
Published in: Animals
Date: August 2025
DOI: https://doi.org/10.3390/ani15172538
Type of access: Open access (click for full article)
Our summary
Theodoro, S.S. et al. (2025) Evaluation of the short-term effects of mirtazapine on appetite stimulants in dogs: A retrospective study and a placebo-controlled trial. Animals, 15 (17), no. 2538.
The aim of this two-part study was to assess the efficacy and safety of mirtazapine as an appetite stimulant in dogs.
The research was conducted at the Small Animal Clinical Nutrition Service of the Teaching Veterinary Hospital of São Paulo State University and consisted of two separate studies, one retrospective and one prospective.
Study 1 was a retrospective review of medical records for dogs presenting anorexia or hyporexia, irrespective of underlying disease. It analysed data from dogs who had been prescribed mirtazapine as a second-line option, following owners declining the placement of a feeding tube.
Out of 189 inappetent dogs were recommended mirtazapine within the study’s timeframe, 82 cases were excluded due to incomplete follow-up records or missed appointments. The remaining cohort was of 107 dogs, 52 receiving mirtazapine and 56 untreated controls, whose owners declined treatment.
The data analysed found significant differences between groups, as the mirtazapine group showed superior appetite stimulation (68.6%) compared to the controls (37.5%).
Study 2 was a double-blind, randomised, two-day crossover clinical trial performed on dogs presenting with anorexia or hyporexia lasting from one to three days, irrespective of underlying disease. The experimental design consisted of an alternating sequence in which each animal served as its own control: one patient received mirtazapine on the first day and a placebo on the second day, while the following patient received a placebo on the first day and mirtazapine on the second, and so forth. Treatments were initiated within the hospital and continued at home on the second day. Behaviours relating to food intake were then recorded by owners in a standardised monitoring form, and participants returned to the hospital on the third day for a follow-up evaluation.
While 30 animals were initially included in the prospective study, five were excluded due to non-compliance or failure to return for follow-up, leaving a total of 25 patients (14 receiving the mirtazapine-placebo sequence, and 11 the placebo-mirtazapine). All dogs who received mirtazapine on the first day had food acceptance (14/14), a rate higher than the placebo group (7/11). The mirtazapine group as a whole also saw higher proportions in the categories with the highest food intake and saw no extreme food refusal (dogs who had left 76–100% of food).
Another finding was the lack of clinical signs of adverse effects exhibited during follow-up, which suggests good tolerability of mirtazapine at the administered doses, even in patients with systemic diseases.
Limitations of this study are related to the study designs. Due to the retrospective nature of study 1, a large proportion of cases (43.4%) had to be excluded from the cohort, limiting the interpretability of the data. The crossover design of study 2 only allowed assessment of the drug’s effects in the short term and may have created confounding effects due to the timing of the first administration compared to the second one. The prospective study’s limited sample size provides another limitation.
Take home
This study provides some evidence that mirtazapine is a safe and effective appetite stimulant for dogs presenting with anorexia or hyporexia.
The following may also be of interest
WSAVA Global Nutrition Committee (2013) Feeding Guide for Hospitalized Dogs and Cats. [WSAVA] [Online]. Available from: https://wsava.org/wp-content/uploads/2020/08/Feeding-Guide-for-Hospitalized-Dogs-and-Cats.pdf [Accessed 13 January 2026]
Veterinary Medicines Directorate (2025) SUMMARY OF PRODUCT CHARACTERISTICS: Mirtazapine. [VMD] [Online]. Available from: https://www.vmd.defra.gov.uk/ProductInformationDatabase/files/SPC_Documents/SPC_3025132.PDF [Accessed 13 January 2026]
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