Mirtazapine for Cats: Appetite Stimulant Uses & Dosage

This information is for educational purposes only. Never give your pet any medication without your veterinarian's guidance. Dosing, frequency, and safety depend on your pet's specific health profile.

Mirtazapine is a prescription medication your vet may use to help a cat who is eating poorly, losing weight, or feeling nauseated. In cats, it is most often used as an appetite stimulant with added anti-nausea and anti-vomiting effects. It comes in oral forms, such as tablets or compounded liquid, and as an FDA-approved transdermal ointment for cats called Mirataz, which is applied to the inner ear.

Although mirtazapine was originally developed as a human antidepressant, veterinary teams commonly use it to support cats with inappetence from medical problems like kidney disease, GI disease, liver disease, pancreatitis, or cancer care. The transdermal option can be especially helpful when a cat resists pills or is not eating well enough to hide medication in food.

This medication does not treat the underlying cause of appetite loss by itself. Instead, it is usually part of a broader plan that may also include diagnostics, fluids, anti-nausea medication, pain control, diet changes, and close follow-up with your vet.

Your vet may prescribe mirtazapine when your cat has decreased appetite, unintended weight loss, nausea, or vomiting. It is commonly used as supportive care in cats with chronic kidney disease, GI upset, liver disease, pancreatitis, and some cancer or chemotherapy-related nausea. In practice, it is often chosen when a cat needs help eating while the underlying illness is being investigated or treated.

Mirtazapine can be useful when poor appetite creates a second problem: not taking in enough calories. Cats that eat too little for too long can become weak, dehydrated, and at risk for serious complications related to prolonged anorexia. That is why your vet may recommend appetite support sooner rather than later, especially in older cats or cats already losing weight.

It is important to remember that appetite loss is a symptom, not a diagnosis. If your cat is hiding, vomiting, drooling, losing weight, or refusing food for more than a day, your vet may want bloodwork, urinalysis, imaging, or other testing before deciding whether mirtazapine is the right option.

Always use the exact dose and schedule your vet prescribes. In published veterinary references, a common oral dose for cats is 1.88 mg by mouth every 72 hours, while the FDA-approved transdermal feline product is 2 mg per cat applied to the inner pinna every 24 hours. The labeled Mirataz course is typically used for 14 days. Your vet may adjust the plan based on your cat's size, diagnosis, response, and whether kidney or liver disease could slow drug clearance.

Do not switch between oral and transdermal forms on your own. These products are not always interchangeable dose-for-dose, and compounded transdermal products may absorb unpredictably. If your cat has chronic kidney disease or liver disease, your vet may choose a lower frequency, closer monitoring, or a different appetite-support plan.

If you miss a dose, contact your vet for guidance. In many cases, they will advise giving it when remembered unless it is close to the next scheduled dose. Do not double up. For transdermal Mirataz, wear gloves, apply only to the inner ear flap as directed, rotate ears when instructed, and prevent people or other pets from contacting the treated area for about 2 hours after application.

Many cats tolerate mirtazapine reasonably well, but side effects can happen. The most commonly reported problems are ear-site reactions with the transdermal product, increased vocalization, hyperactivity or agitation, and vomiting. Some cats also seem sleepy, restless, or a little unsteady.

More concerning signs can suggest excessive drug effect or serotonin-related toxicity. Call your vet promptly if you notice marked agitation, tremors, incoordination, heavy drooling, repeated vomiting, unusual pacing, or behavior that seems dramatically different from your cat's normal personality. Rare allergic reactions or blood-related abnormalities have also been reported.

Cats with kidney or liver disease may clear the drug more slowly, so side effects can last longer or appear at lower doses. If your cat stops eating completely, seems painful, or develops worsening lethargy despite treatment, your vet may want to reassess the underlying illness rather than continue appetite stimulation alone.

Mirtazapine can interact with other medications that affect serotonin or monoamine pathways. It should not be used with monoamine oxidase inhibitors (MAOIs), and veterinary references specifically warn against combining transdermal mirtazapine with MAOIs such as selegiline or amitraz, or using it within 14 days of those drugs.

Your vet will also use caution if your cat takes other serotonergic or centrally acting medications. Examples commonly listed in veterinary references include SSRIs such as fluoxetine, tricyclic antidepressants such as clomipramine, tramadol, diazepam, and cimetidine. These combinations do not always mean the drug cannot be used, but they may change monitoring, dose selection, or whether another appetite-support option is safer.

Before starting mirtazapine, tell your vet about every medication and supplement your cat receives, including flea and tick products, compounded medications, calming supplements, and any human medications accidentally given at home. That full medication history helps your vet lower the risk of interactions and choose the most appropriate care plan.