Mirtazapine for Cats (Mirataz)

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 Cats?

Mirtazapine is a prescription appetite stimulant used in cats to help treat unintentional weight loss caused by medical conditions like cancer, gastrointestinal (digestive tract) disease, and other internal conditions (liver disease, kidney 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 transdermal ointment (which is absorbed through the skin), and when compounded, as an oral liquid and a capsule. 

Is Mirtazapine FDA-Approved? 

Mirtazapine transdermal ointment is FDA-approved in cats to help prevent unwanted weight loss under the brand name Mirataz. 

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

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. 

Mirtazapine Considerations for Cats

Mirtazapine should not be used in cats who are hypersensitive to the medication.

Mirtazapine should be used with caution in cats with liver disease and kidney disease.

At the time of this publication, studies had not not been performed to evaluate the safety and effectiveness of mirtazapine in cats weighing less than 4.4 lb. (2 kg); kittens younger than 6 months old; and in breeding, pregnant, and nursing cats.

Giving mirtazapine with certain medications can result in health risks to your cat, so it’s important to discuss your cat’s medications, including vitamins and supplements, and medical conditions, with your veterinarian. 

How Mirtazapine Works in Cats

Mirtazapine is an antidepressant that affects multiple pathways in a cat’s body. It works by blocking certain chemical messengers in the brain that trigger nausea, vomiting, and suppress appetite. This makes it especially helpful for cats who are not eating due to illness or treatment side effects. 

How To Give Mirtazapine to Cats

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

If administering a transdermal version of this drug: 

• Do not administer orally, to the eye, or directly into the ear canal.  

• Avoid contact with the treated area for two hours after administration. 

• Wear gloves when administering; dispose of used gloves and wash hands after each application. 

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 cat’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 Cats

Mirtazapine is tolerated well in cats. 

The most common side effects of mirtazapine in cats are related to application site reactions such as redness or irritation.  

Other side effects in cats include: 

• Increased vocalization  

• Vomiting 

• Hyperactivity 

• Drowsiness or sedation 

• Allergic reaction (difficulty breathing, hives, facial swelling) 

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

Human Side Effects 

Due to possible side effects, humans should never use medicine dispensed for their pets and pets should not be given any medicine dispensed for a human’s use. Mirtazapine frequently has human dosages that are different from those prescribed for your pet by a veterinarian. 

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

In the event of accidental skin exposure to mirtazapine, wash the affected area thoroughly with soap and warm water.  

In the event of accidental eye exposure to mirtazapine, flush eyes thoroughly with water. 

If skin or eye irritation occurs, seek medical attention. 

Monitoring Your Pet 

No specific monitoring is required for this medication, but your veterinarian may recommend routine testing depending on your cat’s individual needs, other medications they may be prescribed, and/or the issue that initially caused your cat to be placed on this medication. 

Upon stopping mirtazapine transdermal ointment (Mirataz), it’s very important to monitor your cat's food intake. Call your veterinarian if your cat: 

• Eats significantly less than usual, especially if they’re eating less than a quarter of their normal amount for several days 

• Stops eating altogether for more than 48 hours 

When To Call Your Vet 

Call your veterinarian if you see any of the following, or if you have additional questions or concerns about the use of mirtazapine: 

• Severe side effects (above) 

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

• You see or suspect an overdose 

Mirtazapine Overdose Concerns in Cats

The most common signs of overdose in cats are:  

• Vocalization 

• Agitation 

• Vomiting 

• Ataxia (lack of balance or coordination) 

• Restlessness 

• Tremors (trembling) 

• Excessive drooling 

• Increased respiratory rate 

• Increased heart rate 

• Lethargy 

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 Cats

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.  

• Discard mirtazapine within 30 days of first use.  

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

• Keep out of reach of children and pets.