Transdermal mirtazapine in cats with unintended weight loss (including CKD cats) — LIKELY

In inappetent cats (including cats with chronic kidney disease), does transdermal mirtazapine vs placebo increase appetite and body weight?

Shelf #257 · gate-verified and displayed under the developer's blinded-trial rule

LIKELY: Transdermal mirtazapine produces significant short-term weight gain in cats with unintended weight loss, on the strength of one multi-center, double-blind, placebo-controlled, randomized trial — the licensure trial, stated on the face of this shelf. In Poole 2019 (per-protocol population: 83 mirtazapine and 94 placebo cats with a documented body-weight loss of at least 5%), mirtazapine transdermal ointment 2 mg/cat applied once daily to the inner pinna for 14 ± 3 days gave a mean body-weight change of +3.9% (± 5.4%) versus +0.4% (± 3.3%) on placebo (P < 0.0001), and was well tolerated (mild application-site erythema in 10.4% of mirtazapine cats vs 17.4% on placebo). Two limits are on the face: the trial's endpoint is weight, with no appetite measure reported in the record, and its cats had weight loss from various underlying diseases — it was not a CKD-only trial and reports no CKD subgroup, so the CKD use is as part of that wider weight-losing population (the CKD-specific appetite/weight trial evidence for capromorelin is shelf #258). No mortality or survival claim is made, so this pack is not Tier C. Drafted Nov 10, 2026 (VetMed build, topic #257); all figures from abstracts fetched and verified at drafting.

Poole 2019: transdermal mirtazapine gave +3.9% body weight in 14 days vs +0.4% on placebo (P < 0.0001) in cats with unintended weight loss

Multi-center, double-blind, placebo-controlled, randomized clinical study (record's own wording, in both the article title and the abstract)

Who: Cats: client-owned cats at least 1 year of age, weighing at least 2 kg, with a documented loss of at least 5% in body weight, in a multi-center, double-blind, placebo-controlled, randomized clinical study — treated once daily for 14 ± 3 days with either 2 mg/cat mirtazapine transdermal ointment (n = 83) or placebo (n = 94) applied to the inner surface of the pinna (per-protocol population, as stated in the record). Physical examination, body weight, complete blood count, serum chemistry and urinalysis were performed prior to treatment and on day 14. The weight loss was associated with various underlying diseases, per the record.

Result: The mean percent change in body weight from day 1 to day 14 was +3.9% (standard deviation ± 5.4%) in the mirtazapine group and +0.4% (± 3.3%) in the placebo group (P < 0.0001, two-sample t test). The most common adverse event was mild erythema at the application site, in 17.4% of placebo and 10.4% of mirtazapine-treated cats. The record concludes that application of mirtazapine transdermal ointment was well tolerated both topically and systemically and resulted in significant weight gain in cats experiencing unintended weight loss associated with various underlying diseases.

Watch out: The proven endpoint is weight over about 14 days, not appetite scores (no appetite measure is reported in the record) and not survival or disease outcomes. The population is cats with unintended weight loss from various underlying diseases — the trial was not restricted to cats with chronic kidney disease and the record reports no CKD-only subgroup, so the CKD application rests on CKD cats being part of this wider inappetent/weight-losing population, not on a CKD-specific result. The figures are the per-protocol population (83 mirtazapine, 94 placebo) as the record states them. This shelf is the single home for this question: it is the same question drafted as treatment topic #176, built once here as topic #257.

Poole M, Quimby JM, Hu T, Labelle D, Buhles W. A double-blind, placebo-controlled, randomized study to evaluate the weight gain drug, mirtazapine transdermal ointment, in cats with unintended weight loss. J Vet Pharmacol Ther. 2019;42(2):179-188. PMID: 30506924. Registry ID: none in the record. MeSH: Administration, Cutaneous · Animals · Appetite Stimulants · Cat Diseases · Cats · Double-Blind Method · Female · Male · Mirtazapine · Ointments · Random Allocation · Weight Gain · Weight Loss

Synthesis: one decisive blinded licensure trial for weight gain — in weight-losing cats generally, not in a CKD-only cohort

Synthesis

Who: Synthesis of the card above: Poole 2019 (multi-center, double-blind, placebo-controlled, randomized clinical study; per-protocol population 83 mirtazapine and 94 placebo cats with at least 5% documented body-weight loss).

Result: A single trial carries this shelf, stated on its face, and on its endpoint it is decisive: +3.9% body weight on transdermal mirtazapine 2 mg/cat daily versus +0.4% on placebo in about 14 days (P < 0.0001), with application-site erythema no commoner on the drug than on placebo (10.4% vs 17.4%). That supports LIKELY for the claim as carded — short-term weight gain in cats with unintended weight loss. For the CKD question that prompted this topic, the honest reading is narrower: cats with CKD and weight loss are the commonest patients of this kind (shelf #258 cards capromorelin's CKD-specific weight trial), but Poole's cohort had various underlying diseases and no CKD subgroup is reported, so a CKD-specific effect size cannot be quoted from this record. No mortality or survival claim is made, so this pack is not Tier C.

Watch out: Fourteen days is a short horizon: the record does not show whether the weight gain is maintained, whether it is lean tissue, or whether it changes the course of the underlying disease — mirtazapine treats the weight loss, not its cause, and the underlying disease still needs its own diagnosis and treatment.

Synthesis of Poole M et al. PMID: 30506924. Registry ID as on the individual card.

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