A clinical comparison of Mirataz (mirtazapine) and Elura (capromorelin) for feline appetite stimulation. Analyze openFDA adverse events, side effects, and patient-fit criteria.

In feline veterinary medicine, inappetence (anorexia or hyporexia) is not merely a symptom of disease; it is a critical clinical challenge. Cats are metabolic outliers. A few days of caloric deprivation can trigger a cascade of peripheral fat mobilization, leading to hepatic lipidosis (fatty liver disease), a potentially fatal syndrome. Furthermore, chronic weight loss in aging cats suffering from chronic kidney disease (CKD), inflammatory bowel disease (IBD), or neoplasia directly correlates with muscle wasting (cachexia) and reduced survival times.

To combat weight loss and stimulate hunger, veterinary teams have two primary FDA-approved appetite stimulants: Mirataz (mirtazapine transdermal ointment) and Elura (capromorelin oral solution).

While both medications share the goal of restoring caloric intake, they work through entirely different biological pathways, require different routes of administration, and exhibit distinct side effect profiles. Choosing the right medication requires a detailed understanding of the patient's underlying comorbidities, especially cardiac disease and diabetes mellitus.

This clinical guide provides a comprehensive pharmacology comparison between Mirataz and Elura. We detail their mechanisms of action, analyze real-world safety profiles using data from the openFDA animal adverse event database, outline patient-selection criteria, and provide administration guidelines for veterinary teams and clients.

Quick answer

What is the difference between Mirataz and Elura for cats, and which is safer?

Mirataz and Elura are both FDA-approved feline appetite stimulants, but they differ in administration, mechanism, and patient safety:

Mirataz (mirtazapine) is a transdermal ointment applied to the inner ear, acting on serotonin and histamine receptors. It is a broad-use stimulant, safe for most cats, including those with diabetes. Its most common side effects are localized ear irritation (erythema, scaling) and behavioral changes (vocalizing, hyperactivity).
Elura (capromorelin) is an oral liquid that mimics the hunger hormone ghrelin. It is specifically labeled for managing weight loss in cats with chronic kidney disease (CKD). However, it must be avoided in cats with diabetes (as it increases blood glucose) and used with caution in cats with cardiac disease (as it causes transient bradycardia and hypotension). Its most common side effects are hypersalivation (drooling), vomiting, and lethargy.
openFDA pharmacovigilance data (as of June 2026) records 1,687 adverse-event reports for feline mirtazapine and 756 for feline capromorelin. For both drugs the highest-frequency terms (anorexia, lethargy, weight loss, lack of efficacy, death) largely reflect the advanced underlying disease being treated rather than direct drug toxicity. The drug-distinctive signals are mirtazapine's application-site dermatitis (erythema, crusting) and serotonergic behavioral signs (vocalization, hyperactivity), versus capromorelin's gustatory hypersalivation, transient bradycardia/hypotension, and hyperglycemia.

Pharmacological profiles and mechanisms of action

To compare these two therapeutics, we must first examine how they interact with the central nervous system to stimulate hunger.

1. Mirataz (Mirtazapine Transdermal Ointment)

Approved by the FDA in 2018 (NADA 141-481, Kindred Biosciences/Dechra), Mirataz contains mirtazapine, a tetracyclic antidepressant. In cats, its appetite-stimulating properties are driven by complex interactions with multiple neurotransmitter receptors:

Alpha-2 Adrenergic Receptor Antagonism: By blocking presynaptic alpha-2 receptors, mirtazapine increases the release of norepinephrine and serotonin in the central nervous system, activating appetite centers in the hypothalamus.
5-HT₂ and 5-HT₃ Serotonergic Receptor Antagonism: Blocking 5-HT₂ receptors contributes to appetite stimulation. Crucially, blocking 5-HT₃ receptors provides a central antiemetic (anti-nausea) effect, making it highly useful for cats where inappetence is driven by persistent nausea.
H₁ Histaminergic Receptor Antagonism: Provides a strong sedative effect in humans, but in cats, it primarily acts to stimulate hunger, although mild somnolence can sometimes occur.
Pharmacokinetics: Mirtazapine is highly lipophilic, allowing it to penetrate the skin when formulated in a transdermal gel. Systemic absorption occurs slowly, with peak plasma concentrations reached within 2 to 4 hours. It is metabolized primarily by the liver via cytochrome P450 pathways and excreted in urine.

2. Elura (Capromorelin Oral Solution)

Approved by the FDA in 2020 (NADA 141-536, Elanco), Elura contains capromorelin, a selective growth hormone secretagogue receptor (GHSR) agonist.

Ghrelin Mimicry: Capromorelin binds directly to the ghrelin receptors in the hypothalamus. Ghrelin is the endogenous "hunger hormone" secreted by the stomach when empty. Binding to this receptor directly signals the brain to initiate eating behavior.
Growth Hormone Pathway Activation: GHSR activation also triggers the pituitary gland to secrete growth hormone (GH), which in turn stimulates the liver to produce Insulin-like Growth Factor-1 (IGF-1). This pathway promotes protein synthesis, muscle retention, and weight gain, which is highly beneficial for combating the lean muscle wasting associated with chronic cachexia.
Pharmacokinetics: Administered orally, capromorelin is rapidly absorbed from the gastrointestinal tract, with peak concentrations achieved within 1 hour. It undergoes extensive hepatic metabolism and is primarily excreted in feces, reducing the clearance burden on compromised kidneys.

openFDA adverse event data analysis

Veterinary teams should supplement manufacturer clinical trial data with real-world pharmacovigilance reports. The openFDA database aggregates post-marketing adverse event reports. While these reports represent voluntary submissions and do not prove direct causality, they reveal drug-specific clinical patterns.

As of June 2026, the openFDA database contains:

Mirtazapine (feline): 1,687 unique adverse event reports
Capromorelin (feline): 756 unique adverse event reports

Counts reflect unique reports (unique_aer_id_number) for cats where the active ingredient matched mirtazapine or capromorelin; a single report can list more than one reaction, so reaction counts are not mutually exclusive.

Top reported reactions in cats (openFDA)

Rank	Mirtazapine (Mirataz)	Reports	Capromorelin (Elura)	Reports
1	Anorexia / not eating	285	Lethargy / depression	166
2	Lethargy / depression	246	Bradycardia / decreased heart rate	131
3	Lack of efficacy	235	Vomiting	124
4	Death by euthanasia	221	Hypersalivation	119
5	Vomiting	202	Anorexia / not eating	104
6	Weight loss	163	Lack of efficacy	103
7	Application-site reddening (erythema)	145	Death by euthanasia	79
8	Death	126	Hypotension	65
9	Behavioural disorder	119	Behavioural disorder	65
10	Vocalisation	113	Hyperglycaemia	44

Passive surveillance caveats

To properly contextualize the openFDA data, clinicians must understand the nature of passive surveillance. The FDA’s Center for Veterinary Medicine (CVM) aggregates reports from veterinarians, pet owners, and manufacturers. However, this database is a collection of voluntary reports (passive surveillance) rather than a controlled clinical trial (active surveillance). This distinction has two major implications: first, the report counts are not incidence rates and cannot prove causality; a report merely indicates that a clinical sign occurred after drug administration, not that the drug caused it. Second, under-reporting is common for minor side effects, while severe events (like seizures or death) are reported more frequently. Crucially, the most frequent terms for both drugs — anorexia, lethargy, weight loss, "lack of efficacy" (235 for mirtazapine, 103 for capromorelin), and death/euthanasia — overwhelmingly reflect the advanced underlying disease in the treated population (CKD, lymphoma, pancreatitis) rather than direct drug toxicity. A cat with terminal gastrointestinal lymphoma that will not eat despite daily Mirataz generates a "lack of efficacy" report driven by the cancer, not the pharmacology. The signal worth acting on sits one layer down: the drug-distinctive reactions.

Clinical interpretation of openFDA patterns

Once the disease-driven terms are set aside, each drug shows a recognizable, mechanism-consistent fingerprint:

Mirataz (Mirtazapine): The drug-distinctive signals are application-site dermatitis — reddening/erythema (145 reports), crusting (103), and irritation — and serotonergic behavioral signs — vocalisation (113) and behavioural disorder (119). Mirtazapine's serotonergic activity can cause mild "serotonin agitation," manifesting as constant meowing, restlessness, or pacing, especially if dosed inappropriately or under-cleared in renal patients. Application-site reactions are a direct result of the transdermal vehicle used to carry the drug through the skin of the pinna.
Elura (Capromorelin): The drug-distinctive signals cluster into three groups, each consistent with its label and pharmacology: a gustatory response — hypersalivation (119), drooling (45), and foaming at the mouth (46); a cardiovascular response — bradycardia / decreased heart rate (131 combined) and hypotension (65), reflecting capromorelin's transient effects on autonomic tone and calcium-channel pathways within 2 to 6 hours of dosing; and a metabolic signal — hyperglycaemia (44 reports), consistent with growth-hormone-pathway activation and the reason Elura requires caution in diabetic cats.

Deep dive: Managing side effects and adverse reactions

To ensure patient safety and client compliance, clinicians must prepare owners for the management of drug-specific side effects.

1. Mirtazapine (Mirataz): Serotonin Agitation and Ear Care

Understanding Serotonin Agitation: When mirtazapine accumulates in a cat's system, it can cause mild serotonin syndrome or "serotonin agitation." The cat may exhibit constant vocalization (meowing), pacing, restlessness, dilated pupils (mydriasis), and tremors. In severe cases of overdose (often due to accidental double-dosing or poor clearance in renal patients), cats can experience severe tremors and seizures.
Mitigation and Washout: If agitation occurs, the dose should be skipped, and the interval should be extended (e.g., from once daily to every 48 hours). If a severe overdose occurs, the serotonin antagonist cyproheptadine can be administered orally at 2 to 4 mg per cat as an antidote to reverse the symptoms.
Ear Care Hygiene: The transdermal ointment can form a crust on the pinna, causing local dermatitis, scaling, and pruritus. Owners must be instructed to wipe the ear clean with a dry, soft tissue before applying the next dose. If the ear becomes inflamed or painful, therapy should be paused, or application shifted to the alternate ear.

2. Capromorelin (Elura): Hypersalivation and Bradycardia

Managing the Gustatory Response: Feline hypersalivation is a direct sensory reaction to Elura's chemical taste. The pH and carrier agent can trigger intense salivation, drooling, or foaming. Instruct owners to:
1. Place the dosing syringe deep into the corner of the mouth to bypass major taste buds.
2. Wipe the muzzle with a damp paper towel immediately after dosing.
3. Follow the dose with a tiny syringe-flush of water (1-2 mL) to clear the taste from the mouth.
Understanding the Bradycardia Pathway: Capromorelin's transient effect on heart rate typically peaks 2 to 6 hours post-dose. It acts on systemic calcium-channel pathways and parasympathetic tone, causing a temporary reduction in heart rate (often dropping by 20% to 30% from baseline). While clinically insignificant in cats with healthy hearts, it can be dangerous for cats with cardiorespiratory disease or those undergoing anesthesia, requiring a temporary drug suspension.

Patient fit and clinical contraindications

Choosing between Mirataz and Elura depends heavily on the cat's primary medical condition and cardiac and endocrine history.

1. Chronic Kidney Disease (CKD)

Elura: Labeled specifically for managing weight loss in cats with CKD. Its ghrelin-receptor pathway is highly effective at slowing muscle wasting (cachexia) associated with chronic uremia. (For the broader IRIS-staged CKD workflow these cats sit inside, see the feline CKD treatment guide.)
Mirataz: Safe to use in cats with CKD, but mirtazapine is cleared by the kidneys. In cats with Stage 3 or 4 CKD, mirtazapine's clearance is reduced by 30% to 50%, prolonging its half-life. Therefore, while the standard label recommends daily application, many clinicians adjust the dosing interval to every 48 to 72 hours in severe renal patients to prevent drug accumulation and serotonin agitation.

2. Diabetes Mellitus

Elura: Contraindicated or requires extreme caution. Capromorelin stimulates the growth hormone (GH) pathway. Growth hormone is a direct antagonist of insulin, promoting gluconeogenesis and insulin resistance. In clinical trials, Elura administration led to transient increases in blood glucose levels. Using Elura in a diabetic cat can destabilize glucose control, increase insulin requirements, or precipitate diabetic ketoacidosis (DKA). (For cats already managed with the SGLT2 inhibitors Bexacat or Senvelgo, this glucose instability is a particular concern — see the SGLT2 inhibitors in cats guide.)
Mirataz: Safe for diabetic cats. It does not affect growth hormone pathways or alter insulin sensitivity.

3. Cardiac Disease

Elura: Contraindicated or requires extreme caution. In safety studies, capromorelin caused a transient decrease in heart rate (bradycardia) and blood pressure (hypotension) within 2 to 6 hours of administration. While well-tolerated by cats with healthy hearts, these cardiovascular changes can precipitate heart failure in cats with underlying hypertrophic cardiomyopathy (HCM) or congestive heart failure (CHF).
Mirataz: Safe for cardiac patients. It does not cause significant alterations in heart rate or blood pressure at labeled doses.

4. Hepatic Insufficiency

Both medications are metabolized by the liver.

Mirataz: Clearance is reduced in cats with hepatic impairment (such as hepatic lipidosis or cholangiohepatitis). Adjust the dosing interval to every 48 hours to prevent side effects like hyperactivity.
Elura: Use with caution; safety has not been fully evaluated in cats with severe liver failure.

Clinical decision workflow by condition

When faced with a patient experiencing inappetence, the veterinary team can use the following clinical pathways to select the optimal stimulant:

Feline Pancreatitis (Acute Flare): Cats are often highly nauseous and painful. Mirataz is preferred due to its 5-HT3 antagonism (anti-nausea properties). The transdermal route avoids oral dosing, which is highly advantageous in a vomiting patient.
Hepatic Lipidosis with E-Tube in Place: Since an enteral feeding tube is already active, appetite stimulants are rarely needed for primary caloric intake. However, during the transition phase (weeks 4-6) to encourage voluntary eating, Mirataz is preferred over Elura. If the cat is nauseous, the antiemetic properties of mirtazapine are beneficial, and it can be dosed transdermally or administered orally through the E-tube.
Lymphoma and Cancer Cachexia: Chemotherapy patients lose lean muscle mass rapidly. Elura is highly suitable here because the growth hormone/IGF-1 pathway actively promotes protein synthesis and muscle retention. However, if the chemotherapy drugs are causing severe nausea/vomiting, Mirataz may be used instead or in sequence.
Advanced CKD (IRIS Stage 3 or 4): Both are options, but Elura is specifically labeled for this purpose. If using Mirataz, the clinician must reduce the dosing frequency to every 48 or 72 hours to prevent toxicity.
Household Factors and Cat Behavior: When evaluating patient fit, the clinician must balance route of administration against metabolic profile. A cat with severe stomatitis or oral ulcers will reject oral Elura liquid, and forcing it will cause pain and tissue damage, making the transdermal Mirataz route the only viable option. Conversely, an aggressive cat that resists ear cleaning and manipulation will likely claw the owner during transdermal application, making once-daily oral liquid hidden in a tiny amount of food or syringed quickly a safer alternative for the owner. Additionally, in multi-cat households, owners must prevent other cats from grooming the treated cat's ears for at least 2 hours post-application. If grooming occurs, the co-housed cat may ingest the mirtazapine, leading to accidental sedation or agitation, a risk that is entirely avoided with Elura's oral route.

Drug-drug interactions

Before prescribing, review the patient's current medication log for potential interactions.

Mirtazapine (Mirataz) Interactions

Monoamine Oxidase Inhibitors (MAOIs): Do not use mirtazapine within 14 days of using an MAOI (such as selegiline or amitraz). Concomitant use can trigger a life-threatening serotonin syndrome crisis (hypotension, hyperthermia, seizures).
Selective Serotonin Reuptake Inhibitors (SSRIs): Use caution when combining with drugs like fluoxetine or clomipramine, as they increase serotonin levels, elevating the risk of serotonin agitation.
Tramadol: Tramadol has weak serotonergic activity. Combining it with mirtazapine increases the risk of serotonin syndrome.

Capromorelin (Elura) Interactions

CYP3A Inhibitors/Inducers: Capromorelin is metabolized by the cytochrome P450 enzyme pathway. Combining it with CYP3A inhibitors (such as ketoconazole or itraconazole) can increase capromorelin concentrations, exacerbating bradycardia.
Insulin: Diabetic cats receiving insulin will likely require close glucose monitoring and insulin adjustments if capromorelin is administered.

Administration and human exposure warnings

Administering medications to a sick, nauseous cat is a common source of stress for owners, directly affecting compliance.

1. Mirataz Administration (Transdermal Ointment)

Mirataz is supplied in a multi-dose tube with a dosing card.

Human Safety Warning: Mirtazapine can cause severe drowsiness, dizziness, and sedation in humans. Because the transdermal vehicle is optimized to transport the drug across skin, owners must wear disposable gloves during application.
Accidental Exposure Protocol: If the ointment comes in contact with human skin, wash the area immediately with soap and water. If accidental eye exposure occurs, flush the eyes with water. Keep children and pregnant women away from the treated cat's ears for at least 2 hours post-application.
Application steps:
1. Wear disposable gloves.
2. Squeeze a 1.5-inch ribbon of ointment onto the dosing card to measure the 2 mg dose.
3. Apply the ointment directly to the inner pinna (ear flap) of the cat's ear. Massage it gently into the skin.
4. Alternate ears daily. Apply to the left ear on Day 1, and the right ear on Day 2.
5. Before applying the next dose, gently wipe the pinna with a dry tissue to remove any residue, preventing crusting and localized skin irritation.

2. Elura Administration (Oral Solution)

Elura is a liquid formulation supplied with an oral dosing syringe.

Client Instructions:
1. Dose is calculated by body weight (2 mg/kg or 0.9 mg/lb once daily).
2. Draw the calculated volume into the provided syringe.
3. Insert the syringe into the corner of the cat's mouth and administer the liquid slowly.
4. Managing Salivation: Many cats dislike the taste of Elura and will drool or foam at the mouth immediately after administration. Instruct owners that this is a transient, sensory reaction, not a sign of toxicity. Wiping the cat's muzzle after dosing can reduce discomfort.

Clinical Comparison Summary

Feature	Mirataz (Mirtazapine)	Elura (Capromorelin)
Route / Form	Transdermal ointment (pinna of ear)	Oral liquid solution
FDA Approval	2018 (NADA 141-481)	2020 (NADA 141-536)
Mechanism	Serotonin (5-HT2, 5-HT3) and alpha-2 antagonist	Ghrelin receptor agonist (GH secretagogue)
Primary Indication	General weight loss and appetite stimulation	Management of weight loss in chronic kidney disease
Drug-distinctive openFDA signal	Application-site dermatitis (erythema, crusting), vocalisation, hyperactivity	Hypersalivation/drooling, bradycardia, hypotension, hyperglycaemia
Diabetes Fit	Safe (does not alter glucose)	Contraindicated (raises growth hormone/glucose)
Cardiac Fit	Safe (no cardiovascular effects)	Use caution (causes transient bradycardia/hypotension)
Dosing in CKD	Safe, but require adjusted interval (e.g., every 48h) in Stage 3-4	Labeled dose (daily), promotes lean mass retention
Route Preference	Preferred for cats that resist oral dosing or have oral pain	Preferred for precise, weight-based titration

Frequently asked questions

Why does my cat drool or foam at the mouth after taking Elura?

Hypersalivation (with drooling and foaming) is the most common Elura-distinctive reaction in openFDA cat data — hypersalivation alone appears in 119 of 756 reports (~16%), and it is also documented as a frequent transient event in Elura's field studies. It is a sensory reaction to the flavor, pH, or texture of the oral liquid rather than a sign of toxicity, and typically resolves within 10 to 15 minutes. Administering a small amount of water or wiping the muzzle can help.

Can I apply Mirataz more than once a day if my cat isn't eating?

No. Do not exceed the labeled once-daily dose. Mirtazapine has a long half-life in cats. Over-application leads to drug accumulation, resulting in severe side effects, including extreme hyperactivity, constant vocalization (meowing), pacing, and tremors. If a cat is not eating despite daily Mirataz, the underlying disease is not controlled, and the cat needs veterinary re-evaluation.

Can Mirataz and Elura be used together?

No. There are no safety studies evaluating the concurrent use of both medications in cats. Because they target different pathways and both have systemic effects, combining them is not recommended. If one medication fails to stimulate appetite, the clinician should discontinue it and switch to the alternative after a 24-to-48-hour washout period.

What if my cat is already on appetite stimulants and still refuses to eat?

Appetite stimulants are not magic pills; they require functional metabolic pathways and a relatively stable digestive tract to work. If a cat is on daily Mirataz or Elura and still refuses to eat for more than 48 hours, the underlying disease (such as a pancreatitis flare-up, renal crisis, or intestinal obstruction) is causing severe, unmitigated nausea or pain. Force-feeding must be avoided. The cat requires immediate veterinary re-evaluation, fluid therapy, and placement of an enteral feeding tube (such as an E-tube) to support recovery.

Can Mirataz or Elura be used for cats with chronic diarrhea or vomiting?

While mirtazapine (Mirataz) blocks 5-HT3 receptors, which provides an anti-nausea benefit, it does not resolve the underlying cause of vomiting or diarrhea (e.g., inflammatory bowel disease, GI lymphoma, or dietary allergies). Capromorelin (Elura) mimics ghrelin and can affect GI motility, but it is not indicated as an antiemetic. Using these drugs without ruling out GI obstruction or active pancreatitis can delay critical care. Always pair appetite stimulation with a diagnostic workup of the gastrointestinal signs.

Sources

FDA CVM approvals: Mirataz (mirtazapine transdermal ointment) FOI Summary NADA 141-481
FDA CVM approvals: Elura (capromorelin oral solution) FOI Summary NADA 141-536
Veterinary Information Network (VIN): Mirtazapine and Capromorelin Clinical Monographs
Journal of Veterinary Internal Medicine (JVIM): Clinical trials on the safety and efficacy of capromorelin and transdermal mirtazapine in cats.

Vet Med Guide

Mirataz vs. Elura for Cats: FDA Adverse Events, Side Effects, and Patient Fit