Overview of Mirtazapine for Canines and Felines
Brand Names and Other 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
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.
- Used for chemotherapy-induced nausea.
- Chronic pain7
Precautions and Side Effects
- While generally safe and effective when prescribed by a veterinarian, Mirtazapine can cause side effects in some animals.
- Mirtazapine should not be used in animals with known hypersensitivity or allergy to the drug. The most common side effect in dogs and cats is drowsiness.
- In cats, side effects may include increased vocalization, increased affection, muscle twitching, agitation, hyperactivity, and other behavioral changes. Lower doses (1.88 mg/cat total dose) resulted in reduced side effects.
- The dosage of Mirtazapine should be decreased by 30% in pets with liver disease, kidney disease or failure.
- The safety of Mirtazapine use in pets pregnant or lactating has not been established.
- Mirtazapine is commonly used with other antiemetic drugs.
- Mirtazapine may interact with other medications. Consult with your veterinarian to determine if other drugs your pet is receiving could interact with Mirtazapine. Such drugs include tramadol, other anti-anxiety medications such as Fluoxetine (Prozac), Diazepam (Valium), lorazepam (Ativan), Clonazepam (Klonopin) or Alprazolam (Zanax). Narcotic drugs, other tricyclic antidepressants, certain antihypertensive medications (Clonidine, propranolol) and some antihistamine can interact with Mirtazapine.
- In cases of overdose or in select pets sensitive to the effects of serotonin, Mirtazapine 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.
How Mirtazapine is Supplied
- Mirtazapine is available as scored film-coated tablets containing 7.5 mg, 15mg or 30 mg of mirtazapine.
- The orally disintegrating tablets are available as 15, 30 and 45 mg of mirtazapine.
Dosing Information of Mirtazapine for Dogs and Cats
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 mg/dose (¼ of a 15 mg pill) per cat every 48 to 72 hours (every 2 to 3 days). A lower dose of 1.88 mg total dose (1/8 of a 15 mg tablet) is recommended in cats with kidney failure.
For use in dogs as an appetite stimulant, the most common dosing is 0.6 mg/kg orally every 24 hours, not to exceed 30 mg/day. A common dosage reference is:
- 3.75 mg per dog PO every 24 hours for dogs < 11 pounds body weight(¼ of a 15 mg pill total dose once daily)
- 7.5 mg per dog PO every 24 hours for dogs 11 to 22 pounds body weight(1/2 of a 15 mg pill total dose once daily)
- 11.25 mg per dog PO every 24 hours for dogs 22 to 33 pounds body weight(3/4 of a 15 mg pill total dose once daily)
- 15 mg per dog PO every 24 hours for dogs 33 to 66 pounds body weight(one 15 mg pill total dose once daily)
- 22.75 mg per dog PO every 24 hours for dogs 66 to 110 pounds body weight
- 30 mg per dog PO every 24 hours for dogs over 110 pounds body weight
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.
Resources & References:
- Plumb's Veterinary Handbook by Donald C. Plumb, 9th Edition
- Giorgi M, Owen H. Mirtazapine in Veterinary Medicine a Pharmacological Rationale for its Application in Chronic Pain. American Journal of Animal and Veterinary Sciences 2012;7:42-46.
- Ferguson L, McLean M, Quimby J. Mirtazapine toxicity in cats: retrospective study of 104 cases (2006-2011). In: Proceedings of the ACVIM Forum. Nashville, TN, USA; 2014.
- Smith C, Tappin S. Mirtazapine as an appetite stimulant in 164 dogs and 68 cats. In: WSAVA/FECAVA/BSAVA World Congress 2012 Proceedings Online. Birmingham, UK; 2012.
- Quimby JM, Lunn KF. Mirtazapine as an appetite stimulant and anti-emetic in cats with chronic kidney disease: a masked placebo-controlled crossover clinical trial. Vet J 2013;197:651-654.
- Quimby JM, Gustafson DL, Lunn KF. The pharmacokinetics of mirtazapine in cats with chronic kidney disease and in age-matched control cats. J Vet Intern Med 2011;25:985-989.
- Casamian-Sorrosal D, Warman S. Use of mirtazapine as an appetite stimulant in dogs and cats: a prospective observational study. In: British Small Animal Veterinary Association 2010 Proceedings Online. Birmingham, UK: British Small Animal Veterinary Association; 2010.
- Textbook of Veterinary Internal Medicine, Ettinger & Felman
- Current Veterinary Therapy XV, Bonagura, and Twedt
- ASPCA Pet Poison Hotline
- Pet Poison Helpline