Mirtazapine

By Rania Gollakner, BS DVM

Medications

What is mirtazapine?

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.

How do I give my pet mirtazapine?

Mirtazapine comes in pill form and is given orally (by mouth). In some cases, your veterinarian may have the pills compounded into liquid form to make oral dosing easier, especially for cats.

This medication should take effect within 1 to 2 days, and improvements in clinical signs should follow.

What if I miss giving my pet the medication?

Give the missed dose as soon as you remember, and then wait the recommended amount of time between doses. Never give your pet two doses at once or give extra doses.

Are there any potential 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.

Are there any risk factors for this medication?

Pets that are allergic or hypersensitive to mirtazapine should not take it. Mirtazapine should be used cautiously in patients with liver and/or kidney disease, with a lower dose is recommended for these cases. Pets with a history of leukemia, low platelets, or any blood disease should use mirtazapine cautiously, and blood test monitoring is recommended.

Are there any drug interactions I should be aware of?

Monoamine oxidase inhibitors (MAOIs) such as amitraz or selegiline, and serotonin reuptake inhibitors (SSRI’s) such as Prozac® (fluoxetine) may interact with mirtazapine, and can cause many of the side effects listed above.

Other drugs that can interact mirtazapine include tramadol, diazepam, and cimetidine, and should be used with caution.

Is there any monitoring that needs to be done with this medication?

Monitor your pet for signs of serotonin syndrome. As with any medication, your pet should be monitored for signs of an allergic reaction, such as breathing difficulties, hives, or facial swelling. Pets with a history or concern of blood disease should have blood work monitored regularly.

How do I store mirtazapine?

This medication should be stored at room temperature and away from excess heat or cold.

What should I do in case of emergency?

If you suspect an overdose or a negative reaction to the medication, call your veterinary office immediately. If they are not available, follow their directions in contacting an emergency facility.

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