What Are the Uses of Mirtazapine for Cats? (with pictures)

Alicia Sparks
Alicia Sparks
Mirtazapine is used in cats for its appetite stimulating.
Mirtazapine is used in cats for its appetite stimulating.

In people, mirtazapine generally stimulates appetite. It also has an anti-nausea effect, reducing vomiting. When cats take the medication, they often experience these same benefits, so the drug can be useful when veterinarians want to make sure animals keep food and water down, or when the goal is to gain or maintain weight. A wide range of conditions can cause this need, but kidney disease, pancreatitis and depression are some of the most common. In some instances, people use this medication in pets because of its antidepressant properties.

How It Works

Mirtazapine helps stimulate appetite in cats and reduces nausea.
Mirtazapine helps stimulate appetite in cats and reduces nausea.

Mirtazapine affects neuroreceptors in the stomach and intestine, making it hard for these organs and the vomit center of the brain to communicate. At the same time in the gut, serotonin, a chemical often associated with feelings of relaxation and comfort, is connected to proper digestion. High levels often trigger diarrhea as the body’s way of getting rid of toxins. This drug typically limits serotonin activity in the bowels, keeping digestion more stable.

Chronic renal failure affects an estimated 20 percent of cats over age 15.
Chronic renal failure affects an estimated 20 percent of cats over age 15.

Even as this substance reduces serotonin’s effects in the intestines and stomach, it usually amplifies them in the brain. It generally makes levels of norepinephrine, a neurotransmitter, go up as well. With a boost of these feel-good chemicals, mood often improves. This is why medical professionals use it to treat emotional imbalances.

Chronic Renal Failure

Chronic renal failure (CRF) or kidney disease affects an estimated 20% of felines over age 15. Veterinarians aren’t sure exactly what causes it in many cases. Even so, they think that tumors, genetic issues, birth defects, infections and damage through other means like injury or poisoning might be linked to the problem.

Similar to what happens with people, when cats experience chronic renal failure, they usually are not able to filter out waste and toxins the way they should. This can lead to the development of anemia, electrolyte imbalances and other conditions, which can cause nausea, vomiting and weight loss. Mirtazapine for cats often reduces these symptoms.


Inflammation of the pancreas, called pancreatitis, is another feline condition that is somewhat of a puzzle to veterinarians. About 10% of cases are thought to be linked to infections, parasites, reactions to certain drugs, genetics or trauma. The other 90%, however, don’t have an identifiable cause. With this illness, cats don’t usually throw up, but they generally become very lethargic and lose their appetite, both symptoms treatable with mirtazapine.

Diabetes Mellitus

Diabetes is an illness in which the body doesn’t produce enough insulin. As a result of the poor production, it isn’t able to metabolize glucose well, so the level of blood sugar goes up. Affecting about 1 out of every 400 cats, the disease is initially recognized through an increase in appetite, but as it progresses, the desire to eat typically drops. Weight loss often is a concern in moderate to advanced cases, which sometimes also include vomiting. Vets usually prescribe mirtazapine for cats when other medications or treatment options are not able to keep the condition under control.

Lethargy, Depression and Anxiety

Sometimes, cats become agitated, lethargic or depressed, either because of their health problems or because of old age. Vets often use mirtazapine to treat these mood problems because of the effects it has on brain chemicals, with the side effects of anti-nausea and increased appetite generally seen as secondary benefits. With felines, this typically is reversed, but because some of them still benefit from the relaxing effects the medication has, veterinarians do occasionally prescribe it to make animals more emotionally comfortable.


A typical prescription for a cat is for one dose every three days. This is only an average, however, and the exact amount needed in milligrams can vary, depending on the animal’s age, current weight and health conditions. Veterinarians usually look at these factors before giving instructions to owners, and they typically make observations to see if the amount is effective. Making one or more adjustments is relatively standard, especially because a pet’s condition can get better or worse over time.

Overdose of mirtazapine for cats is relatively rare, given the twice-a-week dosing schedule and cautious approach of animal doctors. Still, human error occasionally happens, and cats can get into things they shouldn’t. An owner should immediately contact a veterinarian whenever she notices adverse symptoms or unexpected behaviors.

Side Effects and Warnings

Some people experience drowsiness and dry mouth when taking the drug, but whether these are common side effects for animals remains unclear. It typically isn’t an appropriate medication for felines that have liver or hyperthyroid problems, although it still sometimes can work in these circumstances if the veterinarian closely monitors the cat. Serotonin syndrome, a condition in which serotonin levels get too high, can occur. Symptoms include problems such as general hyperactivity, high blood pressure and heart rate, shivering and dilated pupils.

Although few drugs interact with this medication, amitraz, selegiline and fluoxetine are exceptions. When a cat has been prescribed one of these substances, it should not also take mirtazapine. Veterinarians typically check for potential interactions before writing a prescription, but this relies to a large degree on the owner confirming everything the animal currently is taking.

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Discussion Comments


My cat has hyperthyroidosis, kidney disease and now has been diagnosed with diabetes. She also suffers from acid reflux. She is very lethargic, stays in her bed most of the time, getting up for the toilet or a drink. She is on vidalta, famatodine and also mirtazapine. The mirtazpine works for the first night and then everything goes back to the start again. She is nearly 19 years old. I am doing the right thing.


My cat will almost immediately go to his food bowl and start eating when he has been given this in the past -- and again today. He has pancreatitis and just recently, they found a mass in his abdomen, so he really gets nauseated and doesn't want to eat a thing for days, so this rx has been a lifesaver. He has turned himself around about 4 or 5 times, but this time I'm not so sure. It made him want to eat right away, but he is in a lot of pain from his condition. At least, he isn't hungry too.


@anon302611: I have a 16 year old cat and my vet also gave me the Mirtazaprint 15 mg tablets, but she cut them into four pieces. I'm supposed to give Tera 1/4 of the pill every other day.

I got a new prescription of them yesterday. Last night I gave her the 1/4 pill and she "talked and talked and meowed for hours". She also stole my stuffed animals and made a nest for herself.

I think I'm going to cut the 1/4 pill in half so she only gets 1/8th of the pill every other day. The 1/4 seems to be too much these days.

And you giving your cat 1/3 of a pill definitely seems a bit too much.


Our cat is almost 20 and has kidney failure, she was put on special Science Diet K/D and Royal Canine soft can cat food, fluids, and an antibiotic; it has been working pretty good for about 45-60 days, until all of a sudden, her intake went down to half.

Yesterday I was given a 15mg Mirtazapine pill cut into 3 doses; we gave her one dose last night and now the cat makes weird yelping noises, has stopped eating (on day two), eye pupils are huge, she can hardly walk, and she is hardly moving at all. I have no idea what to do next as it is late Saturday afternoon and my vets are not in until Monday? I know one thing: the next dose of this drug will not be given for sure. If it doesn't kill her I will be amazed!


My 14 1/2 year old female Burmese has multiple health issues such as hyperthyroid disease, feline herpes and IB disease. She's lost a lot of weight in the last half year prior to the thyroid problem being diagnosed. Only 8 1/2 pounds at her healthiest adult weight, she was down to six pounds.

The vet put her on the Hills y/d prescription diet and with the mirtazapine, she's recovered most of her weight. The only problem is the constant yowling after we give her the meds. I'm happy with the results and just not ready to let her go. She's well worth the trouble. Love my cat!


@Mykol - I also believe that pets can go through periods of depression.

My cat has always gone through periods where her appetite was better sometimes than others. Usually in the summer when it is hot and she is more active, she loses weight and isn't interested in eating.

In the winter she isn't very active and seems to eat more and gain weight. Many cats are picky eaters and she has always been one of them.

I can't really use her appetite to judge whether she is feeling OK or not. I can tell my cat is under the weather when she has no interest in what is going on outside.

She is an indoor/outdoor cat and when the birds and bugs are flying around, she loves to be outside. We recently moved to a new place and she stopped eating and wouldn't go outside at all.

She weighed 12 pounds before we moved, and dropped down to 8 pounds within a month or so.

She was given a short round of Mirtazapine to see if this would perk her up a little bit and she might start eating again.

Thankfully it did the trick. I think the move was harder on her than I thought it would be, and it just took her awhile to get adjusted and in a new routine.


My aging cat has quite a few health problems which include diabetes and kidney failure. Because of this she has become lethargic and very skinny.

She began taking Mirtazapine and it seemed to work for awhile, but now she is not eating very well again.

It is hard to see your pets have health issues like this as they can't tell you what they are thinking or feeling. You kind of have to guess by the way they are acting and what their appetite is like.

I was at the point where I was willing to try anything so she wasn't so thin and frail but don't know how much longer she will be around.

When she first started taking the Mitrazapine, I noticed an improvement in her, but now it doesn't seem to have much of an effect.


One of my cats is close to 20 years old which is old when it comes to the life span of a cat. He has never been a finicky eater like a lot of cats are.

The older he became, the harder it was to keep the weight off of him and he became a pretty big cat.

When he started losing weight and not eating, I knew something was wrong. My vet ran some tests and couldn't find anything specific that was wrong and attributed it to old age.

She gave him me some Mirtazapine to give my cat to see if that would increase his appetite. Even though it was beneficial for him to lose a few pounds, this was not a healthy way for him to do it.

The medication did seem to help and he showed an interest in eating again. That was about 6 months ago, and he is doing better and seems a little bit more interested in life than he was before.


I find it interesting that Mirtazapine is used for treating depression in adults and wonder if this might also be beneficial for cats.

When I had to put my dog to sleep, I think my cat went through a period of depression. They hung out together all the time, and my cat really missed the companionship.

She would mope around the house and wasn't interested in eating. When I talked to my vet about it he said to watch her for a few weeks and she didn't improve he would put her on some medication.

I am assuming he was talking about something like Mirtazapine. Thankfully, she perked up after a couple of weeks and I never had to go that route.

I also brought home a kitten and think that helped her from being so lonely during the day.

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    • Mirtazapine is used in cats for its appetite stimulating.
      Mirtazapine is used in cats for its appetite stimulating.
    • Mirtazapine helps stimulate appetite in cats and reduces nausea.
      Mirtazapine helps stimulate appetite in cats and reduces nausea.
    • Chronic renal failure affects an estimated 20 percent of cats over age 15.
      Chronic renal failure affects an estimated 20 percent of cats over age 15.