Mirtazapine, commonly known as Remeron®, Soltab®, Zispin, Avanza, Axit, is used as an appetite stimulant and anti-nausea drug for dogs and cats. Mirtazapine can be used in combination with other anti-vomiting drugs.
Mirtazapine is an orally administered drug belonging to the piperazine-azepine group of drug compounds, commonly referred to as the tetracyclic antidepressants, used to treat depression and mood disorders in humans. Other related drugs in this class include tricyclic antidepressants such as desipramine (Norpramin).
How Does Mirtazapine Work for Dogs and Cats?
The exact mechanism of action of mirtazapine is not completely understood. The drug works by raising the levels of neurotransmitters in nerves in the brain, that helps eliminate the sensations of depression in humans, specifically feelings of sadness and gloom. Increased levels of the neurotransmitters norepinephrine and serotonin are associated with feelings of comfort and relaxation.
Brand Names for Mirtazapine
This drug is registered for use in humans only. Mirtazapine was approved by the FDA in 1996.
- Human formulations: Remeron®, Soltab®, and various generics. Soltab® is the orally disintegrating tablets.
- Veterinary formulations: None
Mirtazapine is available as scored film-coated tablets containing 7.5 milligrams, 15 milligrams, or 30 milligrams of medication. The oral disintegrating tablets are available in 15, 30, and 45 milligram tablets.
Uses of Mirtazapine for Dogs and Cats
Mirtazapine is used as an anti-nausea drug and/or appetite stimulant in dogs and cats. It is commonly used to treat nausea in cats secondary to chronic kidney disease, as well as in pets with chemotherapy-induced nausea.
Entyce® for Dogs: An Alternative Appetite Stimulant
For dogs experiencing appetite loss, veterinarians may also recommend Entyce® (capromorelin oral solution). Unlike Mirtazapine, which is a human medication used off-label in veterinary medicine, Entyce is FDA-approved specifically for appetite stimulation in dogs. Capromorelin works by mimicking ghrelin, a natural hormone that stimulates hunger and signals the brain to increase food intake.
Entyce is commonly prescribed for dogs with decreased appetite due to illness, recovery from surgery, chronic disease, or other medical conditions that affect normal eating habits. Because it is available as a flavored oral liquid, it may be easier to administer than tablets in some dogs. Your veterinarian can help determine whether Mirtazapine, Entyce, or another treatment is the most appropriate option based on your dog's underlying condition and overall health.
Mirtazapine for Dogs and Cats: Precautions and Side Effects
While generally safe and effective when prescribed by a veterinarian, Mirtazapine can cause side effects in some animals. In cats, side effects may include increased vocalization, increased affection, muscle twitching, agitation, hyperactivity, and other behavioral changes. The most common side effect in dogs is drowsiness.
In cases of overdose or in select pets sensitive to the effects of serotonin, the drug can cause tremors, agitation, elevated heart rate, elevated body temperature, high blood pressure, difficulty breathing, and/or dilated pupils. Cyproheptadine can be used as an antidote. Mirtazapine should not be used in animals with known hypersensitivity or allergy to the drug.
Mirtazapine may interact with other medications. Consult with your veterinarian to determine if other drugs your pet is taking could interact with Mirtazapine. Such drugs include tramadol, fluoxetine (Prozac), Diazepam (Valium), lorazepam (Ativan), Clonazepam (Klonopin), and Alprazolam (Zanax). Narcotic drugs, other tricyclic antidepressants, certain antihypertensive mediations (Clonidine, propranolol), and some antihistamines can also interact with Mirtazapine.
Dosage Information of Mirtazapine for Cats and Dogs
Medication should never be administered without first consulting your veterinarian.
If your dog is not eating, it is recommended to work with your veterinarian to help determine the underlying cause.
For use in cats as an appetite stimulant, the most common dosing is 3.75 milligrams/dose (¼ of a 15 milligram pill) per cat every 48 to 72 hours (every 2 to 3 days). A lower dose of 1.88 milligram total dose (1/8 of a 15 milligram tablet) is recommended in cats with kidney failure.
For use in dogs as an appetite stimulant, the most common dosing is 0.6 milligram/kilogram orally every 24 hours, not to exceed 30 milligrams/day. A common dosage reference for dogs is:
- Under 11 pounds: 3.75 milligrams every 24 hours (¼ of a 15-milligram pill)
- 11 to 22 pounds: 7.5 milligrams every 24 hours (1/2 of a 15-milligram pill)
- 22 to 33 pounds: 11.25 milligrams every 24 hours (3/4 of a 15-milligram pill)
- 33 to 66 pounds: 15 milligrams every 24 hours (one 15-milligram pill)
- 66 to 110 pounds: 22.75 milligrams every 24 hours (roughly one and a 1/2 pills)
- Over 110 pounds: 30 milligrams every 24 hours (two 15-milligram pills)
The duration of administration depends on the condition being treated, response to the medication and the development of any adverse effects. Be certain to complete the prescription unless specifically directed by your veterinarian. Even if your pet feels better, the entire treatment plan should be completed.
