Mirtazapine for Dogs

PetMD’s medications content was written and reviewed by veterinary professionals to answer your most common questions about how medications function, their side effects, and what species they are prescribed for. This content shouldn’t take the place of advice by your vet.  

What Is Mirtazapine Used for in Dogs?

Mirtazapine is an appetite stimulant used in dogs to help treat weight loss caused by conditions like cancer, liver disease, kidney disease, and gastrointestinal (digestive tract) disease. These illnesses can cause nausea, which often leads to a loss of appetite and, in turn, reduced food intake.  

Mirtazapine can also be used to counteract weight loss caused by chemotherapy. 

Mirtazapine is available as a generic tablet and, when compounded, as an oral liquid and a capsule.

Mirtazapine is also a prescription medication used in people to treat depression and as an appetite stimulant. 

Is Mirtazapine FDA-Approved? 

While mirtazapine transdermal ointment is FDA-approved in cats to help prevent unwanted weight loss under the brand name Mirataz, it is not currently FDA-approved for use in dogs as a veterinary medication—as an ointment, tablet, or other form.

Mirtazapine is, however, readily utilized in the veterinary field and veterinarians can legally prescribe certain human drugs for use in animals in certain circumstances. This is called extra-label or off-label use because this use isn’t described on the drug label. 

Speak with your veterinarian about whether mirtazapine is right for your dog. 

Compounded Mirtazapine 

In certain circumstances, your vet may recommend a compounded formulation of mirtazapine.

Compounded medications are prescribed, for example, if:  

• There’s a specific reason your pet’s health can’t be managed by an FDA-approved drug, such as if your pet has trouble taking pills in capsule form 

• The dosage strength is not commercially available 

• The pet is allergic to an ingredient in the FDA-approved medication  

Compounded medications are not FDA-approved. They are formulated by your veterinarian and dispensed either by a licensed pharmacist or veterinarian on an individual basis to best suit a patient’s particular needs. 

How Mirtazapine Works in Dogs

Mirtazapine is an antidepressant medication that works through several pathways in the body. Mirtazapine blocks the chemical messengers in the brain that trigger nausea, vomiting, and appetite suppression. 

How To Give Mirtazapine to Dogs

Follow the directions on the drug label or as provided by your veterinarian. 

Generally, your veterinarian will instruct you to give mirtazapine once daily by mouth to your dog.  

Missed a Dose? 

Speak with your veterinarian about what to do if you forget to give a dose of mirtazapine. 

Generally, your vet may instruct you to give it when you remember, or if it is almost time for your pet’s next dose, to skip the missed dose and resume your normal dosing schedule.  

Do not give extra or double doses. 

Possible Side Effects of Mirtazapine in Dogs

Mirtazapine is well-tolerated in dogs.

At the time of publication, limited data evaluating the side effects of mirtazapine in dogs exists.

If you believe your pet may be experiencing any side effects of mirtazapine, consult with your veterinarian. 

Human Side Effects 

While mirtazapine is also a human prescription medication, there are different dosages and side effects that can occur in humans. Humans should never use medicine dispensed for their pets and pets should not be given any medicine dispensed for a human’s use. 

If you accidentally ingest a pet medication, seek medical attention in person or call Poison Control at 800-222-1222. 

Monitoring Your Pet 

Typically, beyond monitoring your dog’s response to mirtazapine, no specific monitoring is required, but your veterinarian may recommend routine testing depending on your dog’s individual needs, other medications they may be on, and/or the issue that initially caused your dog to be placed on this medication. 

Upon stopping mirtazapine, it’s very important to monitor your dog’s food intake. If your dog eats significantly less than usual or stops eating altogether for more than 48 hours, call your veterinarian. 

When To Call Your Vet 

Call your veterinarian if you see any of the following: 

• Severe side effects (above) 

• Your pet’s condition worsens or does not improve with treatment 

• You see or suspect an overdose 

• If you have additional questions or concerns about the use of mirtazapine 

Mirtazapine Overdose Concerns in Dogs

At the time of this publication, studies have not been performed to evaluate the toxicity of mirtazapine in dogs. 

If you suspect an overdose, immediately seek emergency veterinary care or contact an animal poison control center. Consultation fees often apply. 

• Pet Poison Helpline 855-764-7661  

• ASPCA Animal Poison Control 888-426-4435  

How To Store Mirtazapine for Dogs

Keep the following storage tips in mind for this medication: 

• Mirtazapine should be stored at controlled temperatures below 77 F (25 C).  

• Always confirm storage requirements by reviewing the label.  

• Compounded medications should be stored according to the compounding pharmacy’s label. 

• Keep out of reach of children and pets.