Mirtazapine (brand name: Remeron) is similar to tricyclic anti-depressants. It is used most commonly by veterinarians to treat nausea, vomiting, and appetite loss, mainly in cats. Rarely, it may be used to treat behavioral problems. Managing an anorectic cat is always a concern in private veterinary practice since cats often respond to the presence of illness by not eating. Cats that do not eat do not heal as quickly, and some will not recover at all. Several medications have been tried historically. One that has fairly recently come on the market, mirtazapine, has shown promise as a safe and effective alternative. But like many medications, it is not without limitations and adverse effects.


Mirtazapine is a tetracyclic anti-depressant that is prescribed by veterinarians to treat a wide range of conditions, from behavioral problems to loss of appetite in cats. Mirtazapine is particularly useful for patients with anxiety and sleep disturbance. It has a rapid onset of action in comparison to many anti-depressant medications. It has a dual mechanism of action, being both a noradrenergic and specific serotonergic drug (NaSSA). Mirtazapine is metabolized primarily by the liver.

Features of Mirtazapine For Cats

What makes mirtazapine special in veterinary medicine is one of the side effects: weight gain. To better understand this, let’s have a quick look at how mirtazapine acts in the feline body: The nervous system coordinates and controls the body’s activity and functions. Neurons are the primary cell on the nervous system, and they are responsible for transmitting information through the body.

Neurotransmitters are one of the components of the nervous system, and they allow messages from neurons to pass from one cell to another cell in the nervous system. When neurotransmitters arrive at a cell (neuron), they have to bind to receptors. These receptors will determine if the information will continue to pass through the body, or it will inhibit the signal from advancing. 

Side effects from mirtazapine

Mirtazapine is generally well tolerated but side effects are possible. The most common side effect is drowsiness. Other possible side effects that may indicate serotonin syndrome (too much serotonin) include high or low blood pressure, high or low heart rate, vocalization, agitation, vomiting, incoordination while walking, restlessness, and tremors; please contact your veterinarian if you see signs of serotonin syndrome. Rarely, this drug can cause abnormalities in the bone marrow.This short-acting medication should stop working within 24 hours, although effects can be longer in pets with liver or kidney disease.

Use/benefits of Mirtazapine in Cats  

As mentioned earlier, mirtazapine increases appetite and reduces vomiting. Your veterinarian may prescribe mirtazapine for your cat to help with ailments that produce weight loss and nausea, including:  

  • Liver disease and chronic kidney disease. Your vet will monitor the use of mirtazapine with caution as cats with CKD and liver disease may be slower at clearing mirtazapine from their system. 
  • Gastrointestinal disorders such as inflammatory bowel disease and pancreatitis.
  • Hyperthyroidism.
  • Cancer. Mirtazapine may be used to mitigate nausea and decreased appetite related to chemotherapy.

Precautions for Using Mirtazapine

Mirtazapine should not be prescribed or administered to a patient that is hypersensitive or allergic to the medication. It also should be used with caution whenever the animal is taking other medications, as it can interact with other drugs, including Tramadol and monoamine oxidase inhibitors.

Dosage and Administration of Mirtazapine

Mirtazapine is available from compounding pharmacies in varying strengths of oral and topical formulations. The dosage, formulation, and frequency of administration are determined according to what the drug is being used to treat and the type and size of animal receiving the treatment. Since this medication is an anti-depressant, abrupt cessation of the drug is not recommended. The animal should be weaned off mirtazapine over an acceptable period of time.

Prices of Mirtazapine For Cats

$39.95  – $87.97

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