Last updated: May 6, 2026

Mirtazapine for Cats: The Appetite Stimulant That Helps Cats Eat

Few things are more alarming for a cat owner than watching their pet refuse food. A cat that will not eat is a cat in trouble — feline bodies are not designed to go without calories for long, and even two or three days of complete food refusal can trigger a dangerous condition called hepatic lipidosis, or fatty liver disease. When a cat stops eating due to illness, surgery, or chronic disease, veterinarians need a reliable way to restart appetite quickly. That is where mirtazapine for cats enters the picture.

Mirtazapine has become one of the most widely prescribed appetite stimulants in feline medicine. Whether your cat is battling kidney disease, recovering from a procedure, or dealing with nausea that makes food unappealing, there is a good chance your veterinarian will mention this medication. This guide covers everything cat owners need to know — how mirtazapine works, how it is given, what side effects to watch for, and how it compares to other options on the market.

What Is Mirtazapine?

Mirtazapine is a drug originally developed for humans as an antidepressant. It belongs to a class of medications called tetracyclic antidepressants, and in human medicine it is sold under the brand name Remeron. One of its most well-known side effects in people is increased appetite and weight gain — a drawback for human patients but a valuable therapeutic benefit when applied to cats who have lost interest in eating.

In veterinary medicine, mirtazapine is used off-label as an appetite stimulant for cats and, less commonly, for dogs. The FDA also approved a transdermal formulation specifically for cats called Mirataz in 2018, making it the first and only FDA-approved appetite stimulant for feline use. This approval was a significant development because it gave veterinarians and cat owners a purpose-built product with established dosing guidelines for cats rather than relying solely on repurposed human tablets.

Mirtazapine works on multiple receptor systems in the brain and gut, which is part of what makes it so effective. It is not simply an appetite pill — it addresses several of the reasons a sick cat might refuse food, including nausea, serotonin-driven appetite suppression, and general malaise.

How Mirtazapine Stimulates Appetite in Cats

Understanding why mirtazapine for cats works requires a brief look at how appetite is regulated in the feline brain. Several neurotransmitters influence whether a cat feels hungry or nauseous, and mirtazapine interacts with multiple pathways simultaneously.

Mirtazapine blocks specific serotonin receptors — particularly 5-HT2C and 5-HT3 receptors — that play a role in suppressing appetite and triggering nausea. By antagonizing these receptors, the drug removes chemical signals telling the brain that the cat should not eat. The 5-HT3 blockade is especially important because it provides a direct anti-nausea effect, which is critical for cats whose food refusal is driven by feeling sick rather than simply not being hungry.

The drug also increases norepinephrine and serotonin activity through other pathways, which contributes to an overall improvement in mood and alertness. A cat that feels slightly more energetic and less miserable is more likely to approach its food bowl. Additionally, mirtazapine has antihistamine properties — it blocks H1 receptors — which can further reduce nausea and may contribute to sedation at higher doses, though at the low doses used for appetite stimulation in cats, increased activity is more common than drowsiness.

The combined result is a cat that feels less nauseous, more alert, and genuinely hungry — often within a few hours of receiving the medication. Many owners report that their cat walks to the food bowl and eats with enthusiasm for the first time in days or weeks after the first dose.

Transdermal Mirataz vs. Oral Mirtazapine

Mirtazapine for cats is available in two primary forms: oral tablets and a transdermal ointment applied to the inner ear flap. Each has advantages and trade-offs, and the right choice depends on the cat and the situation.

Oral mirtazapine typically involves using a small portion of a human-formulated tablet. Because human tablets come in 7.5 mg, 15 mg, and 30 mg doses — far too high for a cat — the tablet must be cut or a compounding pharmacy must prepare a smaller dose. Oral administration works well for cats who tolerate pilling or who will accept crushed medication mixed into a small amount of food. The drug is absorbed through the gastrointestinal tract and typically begins working within one to two hours. The major drawback is that many sick cats are difficult to pill, and cats with active nausea may vomit the tablet before it can be absorbed.

Transdermal Mirataz is a 2% mirtazapine ointment applied in a thin strip to the inner pinna — the hairless skin inside the ear flap. It was specifically developed to solve the pilling problem. A measured dose is squeezed from a tube and rubbed gently onto the ear using a gloved finger. The drug absorbs through the skin and enters the bloodstream without requiring the cat to swallow anything. This is especially valuable for cats who are vomiting, extremely resistant to oral medication, or whose owners struggle with pilling. Mirataz reaches effective blood levels within a few hours and provides steady appetite stimulation over the dosing interval.

The transdermal route also avoids first-pass metabolism in the liver, which means the drug reaches the bloodstream more directly. This can be an advantage for cats with liver compromise. On the other hand, Mirataz tends to cost more than generic oral mirtazapine, and some cats develop mild skin irritation at the application site. Owners must wear gloves when applying it to avoid absorbing the drug themselves.

Dosing Mirtazapine for Cats

Proper dosing of mirtazapine for cats is essential because cats metabolize this drug much more slowly than humans or dogs. An incorrect dose can lead to serious side effects, and dosing also varies depending on whether the cat has normal kidney and liver function.

Oral mirtazapine dosing: The standard dose for a healthy adult cat is 1.88 mg (one-quarter of a 7.5 mg tablet) given every 48 to 72 hours. Cats with chronic kidney disease or liver disease metabolize mirtazapine more slowly, so the dose is often reduced or the interval extended — typically 1.88 mg every 72 hours or longer, depending on the severity of organ compromise. Your veterinarian may also prescribe a custom dose from a compounding pharmacy for more precise dosing.

Transdermal Mirataz dosing: The FDA-approved dose is a 1.5-inch ribbon of ointment (approximately 2 mg of mirtazapine) applied to the inner ear flap once every 24 hours, alternating ears each day. This dosing was established through clinical trials and is printed on the product label. Because the transdermal route provides slower, steadier absorption, daily dosing is appropriate even though oral dosing requires longer intervals between doses.

Never adjust your cat’s mirtazapine dose without consulting your veterinarian. Overdose can cause serious neurological symptoms including tremors, agitation, and serotonin syndrome.

How Often Is Mirtazapine Given to Cats?

The frequency of mirtazapine administration depends on the formulation and the individual cat’s health status. This is one of the areas where veterinary guidance is most important, because getting the interval wrong can lead to drug accumulation and toxicity.

For oral mirtazapine, the typical schedule is every 48 hours (every other day) for cats with normal organ function, or every 72 hours (every third day) for cats with kidney or liver disease. Some older references recommend every 72 hours as the standard for all cats, reflecting earlier pharmacokinetic studies. Your veterinarian will determine the right interval based on your cat’s bloodwork and response.

For transdermal Mirataz, the recommended frequency is once daily. The transdermal formulation was specifically designed for daily application, and clinical trials demonstrated both safety and efficacy at this interval. Most veterinarians recommend a treatment course of 14 days initially, with reassessment afterward to determine whether continued use is warranted.

Mirtazapine is not intended as a permanent solution in most cases. It is a bridge — a tool to keep the cat eating while the underlying cause of appetite loss is addressed. Some cats with chronic conditions may need intermittent or long-term use, but this should always be managed under ongoing veterinary supervision.

Side Effects of Mirtazapine in Cats

Mirtazapine is generally well tolerated at correct doses, but it does produce noticeable behavioral changes in many cats. Understanding what is normal and what warrants a call to your veterinarian helps owners use the medication confidently.

Vocalization and restlessness are the two most commonly reported side effects of mirtazapine for cats. Many owners describe their cat becoming unusually vocal — meowing, yowling, or making persistent sounds — within a few hours of receiving the medication. The cat may also pace, seem unable to settle, or appear agitated. These behaviors are generally mild and self-limiting, resolving within several hours as the peak drug effect passes. They are more common with oral dosing than with the transdermal formulation, likely because oral administration produces a sharper spike in blood levels.

Increased affection and attention-seeking are frequently reported alongside the restlessness. Some cats become unusually clingy, rubbing against their owners, purring loudly, or demanding interaction. While not harmful, it can be surprising if you are not expecting it.

Other possible side effects include tremors, increased heart rate, diarrhea, and in rare cases, serotonin syndrome — a potentially serious condition caused by excessive serotonergic activity. Signs of serotonin syndrome include muscle rigidity, high body temperature, disorientation, and seizures. This is most likely to occur with overdose or when mirtazapine is combined with other serotonergic drugs. If you observe any of these symptoms, contact your veterinarian or an emergency clinic immediately.

At the application site, Mirataz can occasionally cause redness, flaking, or mild irritation of the ear skin. Rotating between ears with each application helps minimize this. If significant irritation develops, your veterinarian may switch to oral dosing.

When Is Mirtazapine Prescribed for Cats?

Veterinarians prescribe mirtazapine for cats across a wide range of clinical situations. The common thread is always the same: the cat is not eating enough to maintain its health, and nutritional support is urgently needed.

Chronic kidney disease (CKD): This is perhaps the single most common reason mirtazapine is prescribed for cats. CKD causes a buildup of uremic toxins in the bloodstream that suppress appetite and cause nausea. Many cats with kidney disease gradually eat less and less, losing dangerous amounts of body weight and muscle mass. Mirtazapine combats both the nausea and the appetite suppression, helping CKD cats maintain caloric intake and body condition. If you are caring for a cat with a chronic condition and considering adoption, our adoption page has resources for connecting with cats who need patient, loving homes.

Cancer: Cats with cancer frequently experience appetite loss due to the disease itself, chemotherapy side effects, or both. Maintaining nutrition during cancer treatment is critical for preserving strength, supporting immune function, and improving quality of life. Mirtazapine helps these cats continue eating through treatment.

Nausea from various causes: Inflammatory bowel disease, pancreatitis, liver disease, and infections can all cause persistent nausea that prevents a cat from eating. Because mirtazapine has direct anti-nausea properties through its 5-HT3 receptor blockade, it addresses the root cause of food refusal in these cases rather than just masking it.

Post-surgical recovery: Cats recovering from surgery often refuse food for one or more days due to anesthesia aftereffects, pain, stress, and nausea. Getting nutrition restarted quickly is important for wound healing and recovery. A short course of mirtazapine can bridge the gap until the cat feels well enough to eat on its own.

Stress-related appetite loss: Major environmental changes — a move to a new home, the addition of a new pet, hospitalization — can cause some cats to stop eating entirely. While addressing the stressor is the primary goal, mirtazapine can prevent dangerous weight loss while the cat adjusts.

How Effective Is Mirtazapine for Cats?

Clinical evidence and veterinary experience both support mirtazapine as one of the most reliable appetite stimulants available for cats. The clinical trials conducted for the Mirataz FDA approval demonstrated statistically significant weight gain in cats receiving transdermal mirtazapine compared to placebo over a 14-day treatment period. Cats in the treatment group gained an average of 3.9% of their body weight, while control cats showed minimal change.

In everyday practice, most veterinarians report that mirtazapine produces a noticeable increase in appetite in the majority of cats who receive it. It does not work for every cat — some individuals show minimal response, particularly if the underlying disease is very advanced — but the overall success rate is high enough that it remains a first-line recommendation for feline appetite stimulation.

Response time is another strength. Many cats begin showing interest in food within two to four hours of oral dosing and within a few hours of transdermal application. For a cat that has not eaten in several days, this rapid onset can be life-saving.

It is important to set realistic expectations: mirtazapine stimulates appetite, but it does not cure the underlying disease. A cat with advanced kidney failure will eat more while on mirtazapine, but the kidney disease continues to progress. Mirtazapine is most effective when used as part of a comprehensive treatment plan that addresses the root cause of illness alongside nutritional support.

Combining Mirtazapine with Anti-Nausea Medications

Because nausea is one of the primary reasons sick cats refuse food, veterinarians sometimes prescribe mirtazapine alongside a dedicated anti-nausea medication for maximum effect. The most common combination is mirtazapine with maropitant (Cerenia) or ondansetron.

Maropitant works by blocking substance P at NK1 receptors in the brain’s vomiting center, while mirtazapine blocks 5-HT3 serotonin receptors. Because these drugs target different anti-nausea pathways, they can work together synergistically — the result is often more complete nausea control than either drug achieves alone. This combination is particularly useful for cats with CKD or cats undergoing chemotherapy, where nausea is severe and multifactorial.

Ondansetron is another anti-emetic that targets 5-HT3 receptors, which overlaps with one of mirtazapine’s mechanisms. While the combination can still be used, veterinarians exercise more caution with it due to the potential for additive serotonergic effects. Your veterinarian will determine the safest combination based on your cat’s specific needs and medication list.

If your cat is on mirtazapine and still not eating well, tell your veterinarian rather than adding medications on your own. The solution may be adding an anti-nausea drug, adjusting the mirtazapine dose, or investigating an underlying cause that has not yet been identified.

Cost of Mirtazapine for Cats

The cost of mirtazapine for cats varies depending on the formulation, the pharmacy, and whether the medication is brand-name or generic.

Generic oral mirtazapine is one of the most affordable prescription medications available. A bottle of 7.5 mg tablets typically costs between five and fifteen dollars at a human pharmacy, and because each tablet is divided into quarters for cat dosing, a single bottle can last weeks or months. Compounded formulations — liquid suspensions or flavored mini-tablets prepared specifically for cats — cost more, usually in the range of twenty to forty dollars per prescription, but they offer more precise dosing and easier administration.

Transdermal Mirataz is more expensive because it is a veterinary-specific, FDA-approved product. A tube of Mirataz typically costs between fifty and ninety dollars depending on the veterinary clinic or pharmacy, and each tube contains enough ointment for approximately two weeks of daily dosing. While the higher price is a consideration, many owners find the ease of ear application — versus the stress of pilling a sick cat — worth the additional cost.

Pet insurance may cover part of the cost of mirtazapine if it is prescribed for a covered condition. Check your policy details or contact your provider for specifics.

Alternatives to Mirtazapine for Cats

While mirtazapine is the most commonly prescribed appetite stimulant for cats, it is not the only option. If a cat does not respond to mirtazapine, cannot tolerate its side effects, or has a contraindication, veterinarians may consider alternatives.

Capromorelin (Elura): Capromorelin is a ghrelin receptor agonist — it mimics the hunger hormone ghrelin to directly stimulate appetite. Elura is the FDA-approved oral solution of capromorelin for cats, specifically indicated for managing weight loss in cats with CKD. It works through a completely different mechanism than mirtazapine, which means it can be effective in cats who did not respond to mirtazapine or can potentially be used alongside it. Capromorelin is given as a flavored oral liquid once daily, which some cats accept more readily than a pill. It tends to be priced similarly to Mirataz.

Cyproheptadine: Cyproheptadine is an antihistamine with serotonin-blocking properties that has been used as an appetite stimulant in cats for decades — long before mirtazapine gained popularity in veterinary medicine. It works by antagonizing serotonin at 5-HT2 receptors, which can increase appetite. Cyproheptadine is inexpensive and available in tablet or compounded liquid form. However, it is generally considered less reliably effective than mirtazapine, and its appetite-stimulating effect is less consistent from cat to cat. It also causes sedation in some cats. Cyproheptadine remains a useful backup option, particularly when cost is a major concern or when mirtazapine is contraindicated.

Other approaches: In some situations, veterinarians may use corticosteroids like prednisolone to stimulate appetite, though these carry significant side effects with long-term use. Warming food, offering highly palatable options like rotisserie chicken or tuna, hand-feeding, and syringe-feeding are non-pharmaceutical strategies that complement any appetite stimulant. For cats with severe, prolonged food refusal, a feeding tube may be placed to provide nutrition directly — this is more common than many owners realize and can be a genuinely effective, low-stress solution for chronically ill cats.

To learn more about different cat breeds and their unique health considerations, visit our cat breeds directory for in-depth breed profiles.

Frequently Asked Questions

How quickly does mirtazapine work in cats?

Most cats begin showing increased interest in food within two to four hours of receiving oral mirtazapine. Transdermal Mirataz may take slightly longer to reach peak blood levels, but appetite improvement is typically noticeable within a few hours of application. The effect generally lasts 24 to 72 hours depending on the formulation and the individual cat’s metabolism. If your cat shows no improvement in appetite after the first dose, contact your veterinarian — the dose or approach may need adjustment.

Can I use human mirtazapine tablets for my cat?

Human mirtazapine tablets can be used for cats, but only under veterinary direction with precise dosing instructions. Human tablets come in strengths far too high for cats — a 15 mg tablet is roughly eight times a typical cat dose — so careful cutting or compounding is essential. Never give your cat a human mirtazapine tablet without first confirming the correct dose with your veterinarian. Overdose can cause tremors, agitation, elevated heart rate, and potentially life-threatening serotonin syndrome.

Is mirtazapine safe for cats with kidney disease?

Yes, mirtazapine is commonly prescribed for cats with chronic kidney disease, and it is one of the most frequent clinical uses of this medication. However, cats with CKD metabolize mirtazapine more slowly than healthy cats, so the dose or dosing interval must be adjusted to prevent drug accumulation. Your veterinarian will typically prescribe a lower dose or extend the time between doses based on your cat’s kidney values. Transdermal Mirataz at its standard daily dose has been studied in CKD cats and is generally well tolerated, but veterinary monitoring remains important.

What should I do if my cat gets too much mirtazapine?

If you suspect your cat has received too much mirtazapine — whether from a dosing error, a double dose, or accidental ingestion of a human tablet — contact your veterinarian or an emergency animal hospital immediately. Signs of mirtazapine overdose in cats include severe agitation, vocalization, tremors, rapid heart rate, disorientation, dilated pupils, and in serious cases, seizures. Early intervention with supportive care and monitoring typically results in a good outcome, but time matters. Do not wait to see whether symptoms develop — call immediately.

Can mirtazapine be given long-term to cats?

Mirtazapine can be used long-term in cats when the underlying condition causing appetite loss is chronic and ongoing, such as CKD or cancer. Many cats receive mirtazapine intermittently or continuously for months or even years under veterinary supervision. Long-term use requires periodic check-ups and bloodwork to monitor for any adverse effects on liver or kidney function. Your veterinarian will help determine whether ongoing use is appropriate for your cat’s specific situation and will adjust the treatment plan as the cat’s condition evolves.

Does mirtazapine make cats sleepy or hyperactive?

At the low doses used for appetite stimulation in cats, mirtazapine more commonly causes mild restlessness, vocalization, and increased activity rather than sedation. Some cats become unusually affectionate and vocal for several hours after receiving the medication. True sedation is uncommon at standard feline doses but can occur in individual cats or at higher doses. If your cat becomes excessively sedated or lethargic after mirtazapine, report this to your veterinarian so the dose can be reevaluated.