What is Mirtazapine for Cats?


Mirtazapine is an antidepressant that is similar to tricyclic. Veterinarians mainly use it in cats to treat loss of appetite, nausea, and vomiting. In rare circumstances, it is used to treat behavioral problems. Mirtazapine is quite helpful for cats with sleep disturbance and anxiety. It acts fast compared to other antidepressant drugs because it has a dual mechanism of being both a serotonergic and noradrenergic drug. The liver mainly absorbs Mirtazapine.

Veterinary Uses of Mirtazapine

Mirtazapine is an appetite stimulant. It is used for cats with feeding problems. Veterinarians also prescribe it as a long-term treatment to cats that experience frequent vomiting, anorexia, and nausea. Anecdotal reports reveal that Mirtazapine is also used in cats with pancreatic, diabetes mellitus, chronic renal failure, and old cats to manage occasional sick conditions. One of the advantages of using Mirtazapine over cyproheptadine is that the latter has antiemetic properties that are useful in treating anorectic cats. Other uses of Mirtazapine include treating behavioral problems like urine spraying, insomnia, and separation anxiety in cats.

Mechanism of Action of Mirtazapine

Mirtazapine is an appetite stimulant. The drug works by reducing the 5HT2c receptors responsible for inhibiting appetite and decreasing the H1 receptors used to control appetite. Mirtazapine also has antiemetic effects that are useful in treating anorexic cats. The antiemetic properties are responsible for weight gain, and they inhibit the 5-HT3 receptors, which are helpful in the physiology of emesis.

How to Administer Mirtazapine to my cat?

Mirtazapine is available as a tablet that is administered orally through the mouth. In some situations, it is advisable to crush the pills and mix them with water to enhance the oral intake of the cats. There should be visible changes in the cat’s appetite within one or two days.

Diabetes Mellitus

Diabetes mellitus is a disease in cats where the body fails to produce enough insulin. Failure to produce enough insulin slows down the metabolism of glucose which in turn causes the blood sugar level to rise. Statistics show that one in every four hundred cats has diabetes. Initially, the disease is recognized by increased appetite, which drops drastically with time. As the disease progresses, the cat experiences weight loss, often accompanied by vomiting. Veterinarians always recommend using Mirtazapine in cats where other medications have not successfully managed the condition.

Chronic Renal Failure

Kidney failure, also called Chronic Renal Failure (CRF), affects cats above the age of 15 years. According to Vcahospitals, it is estimated that 20% of felines suffer from Chronic Renal Failure. It is unknown what causes kidney disease in cats, but studies link the problem to congenital disabilities, tumors, genetic disorders, infections, and other issues like poisoning or injury. In cats, kidney failure displays the same symptoms as in human beings. Chronic renal failure results in the inability to filter toxins and wastes as is supposed to be done by the body. Failure to do so results in other complications such as electrolyte imbalance, anemia, weight loss, nausea, and vomiting. Mirtazapine is prescribed to manage the above symptoms.

Lethargy, anxiety, and depression during old age

When cats become old, they tend to become lethargic, depressed, and agitated because of the health problems associated with old age. Mirtazapine is used to control the above difficulties in cats because it affects brain chemicals. This causes a relaxing effect that makes felines emotionally stable. The other benefit of Mirtazapine is it reduces nausea and increases the appetite of cats.


Pancreatitis is the inflammation of the pancreas. The cause of pancreatitis in cats is unknown, and it is still a puzzle to any vets. Many of the reported cases associated with felines are linked to genetics, trauma, infections, parasites, and reactions to certain medications. One of the significant signs of pancreatitis in cats is they tend to become extremely lethargic and lose appetite. Veterinarians always recommend using Mirtazapine in cats where other medications have not been successful in managing the condition.

Liver Disease

The liver is a vital organ that detoxifies and removes waste products from the body, like chemicals from harmful drugs. It also controls the metabolism of the body. Cancer, parasites, injury, infection, and inflammatory bowel disease are significant causes of liver failure in cats. One of the major symptoms of liver disease in cats is jaundice. When your cat is diagnosed with a liver problem, the vet will administer 1.88mg of oral Mirtazapine for two to three days.


The appropriate beginner oral dosage for Mirtazapine in cats is 1.8 mg per cat instead of 3.75 mg per cat. It is critical for pet owners to know the appropriate dosage and the interval between the recommended dosages. The typically prescribed dosage is one dose every three days on average. However, the exact dosage amount will depend on the cat’s weight, age, and health conditions. Veterinarians consider the above factors before prescribing any dosage. The manufacturers of this drug advise that it is important to divide the 15-mg tablets into the exact dose before sending the prescriptions to clients, which helps to reduce occurrences of accidental overdose. If the conditions worsen over time, a few adjustments may be made to the medications to suit the underlying conditions. The above instructions are not only limited to Mirtazapine but other medical practices.

What if I skip the dosage?

It is advisable that you give the missed dose as soon as you remember, and then you can proceed with the rest of the prescribed doses. It is dangerous to give your cat an extra dose or two doses simultaneously. It can lead to serious side effects such as seizures.

What to do in case of an Emergency

It is rare to overdose on Mirtazapine because it has a twice-a-week dosing schedule. They say human is to error, and in the case of an emergency like an adverse reaction or an overdose, do not hesitate to call your vet immediately. If your doctor is not available or is far away, read the instructions given in the emergency facility and follow the procedures outlined. Also, if you notice any unexpected behaviors in your cat, stop the medication and consult with your vet.

Pharmacokinetics of Mirtazapine

Mirtazapine is available in two doses. Pharmacokinetic studies in felines show that the median half-life of oral Mirtazapine is 9.2 hours for 1.88mg and 15.9 hours for 3.75mg in young cats. There is no significant drug accumulation when the 1.88mg dosage is administered to young cats with no health conditions. Mirtazapine does not show any linear pharmacokinetic in felines. This means that the metabolism of high doses is slower because the enzyme systems tend to be overburdened. Mirtazapine is an appetite stimulant. It is used in cats that have poor feeding habits. A crossover blinded experiment of oral Mirtazapine of 1.88mg in 24 hours and 3.75mg in 24 hours shows that it made the cat ingest more food than before. The difference between the two doses is the side effects which include increased activity, socialization, and vocalization; otherwise, the increase in the amount of food consumption is the same. However, in normal circumstances, starting with the 1.88mg dosage for oral Mirtazapine is recommended, which can be administered daily in young, healthy cats.

Transdermal Mirtazapine for Cats

Transdermal Mirtazapine has been approved by the Food and Drug Administration (FDA) as an effective ointment to manage weight loss in cats. Transdermal administration of drugs is an effective method of administering medications to cats. Mirtazapine is appropriate for transdermal administration, especially in normal young cats. Many vets demonstrate that compounded transdermal Mirtazapine has the required amount of serum concentrations in just small doses. Transdermal Mirtazapine has proved to be reliable to increase food appetite, vocalization, food ingestion, and activity in cats. The only concern about using transdermal Mirtazapine is the high risk involved in the preparation of the ointment and the possibility of contamination of the ingredients used to process the ointments.

Transdermal Mirtazapine for cats Reviews

This product is highly recommended as the only weight gain stimulant that the FDA approves for use in cats. It retails for $ 65.98 in online shipment stores.

Side Effects and Warnings

Vomiting, agitation, restlessness, vocalization, tremors and trembling, lethargy, tachypnea, tachycardia, and excess salivation are some of the most common side effects when a cat takes oral Mirtazapine. These effects can be seen between the first 15 minutes and 3 hours after ingestion of the medication. The side effects can be resolved after one or two days from the time of ingestion. According to Marvistavet, doses of 15 mg and 3.75 mg are primarily associated with signs of toxicity. It is rare to receive any side effects with the 1.88 mg dosage; that is why it is the most efficient dosage to start with, and it’s used in normal young cats.

Drug Interactions with Mirtazapine

Drugs that can be used alongside Mirtazapine include amitraz or selegiline, monoamine oxidase inhibitors, and Prozac, a serotonin reuptake inhibitor. The interaction of these drugs can cause the above-discussed side effects. Other medications such as tramadol, cimetidine, and diazepam should be however be used with caution.

How to monitor your cat during medication

Your cat requires frequent monitoring if it’s on any medication. For Mirtazapine, watch out for signs of serotonin syndrome in your cat. You can also monitor your cat for any allergic reactions, which may include facial swelling, breathing difficulties, and hives. For cats with blood issues like low platelets or with leukemia, appropriate blood tests should be conducted.

Risk Factors of using Oral Mirtazapine

Mirtazapine should not be given to cats that have allergic reactions. It should also not be given to kittens less than six weeks old. Pregnant cats should not be given Mirtazapine as it may interfere with the pregnancy. A lactating cat may be given the drug, but with the help of a vet who will provide the correct prescription. If a lactating cat is given Mirtazapine, it should stay for a period of four days without nursing the kittens. For cats with a history of low platelets or any blood infection such as leukemia, be cautious when giving Mirtazapine. They should also undergo a blood test to monitor their health conditions.

Cautions and Concerns

Mirtazapine is safe to use in cats. It should not be used in cats under six weeks. If you are using the topical profender, it should not be used in kittens below eight weeks. Even the drug can be given with or without food, always ensure that your cat does not take the drug on an empty stomach. Remember to store in a tight container in a cool, dry place away from direct sunlight.

What time of the day should I give my cat Mirtazapine?

Mirtazapine can be administered any time of the day. If you have any questions concerning your pet, please consult with your vet.

How long will my cat be on Mirtazapine?

The package is labeled for daily use for 14 days; please consult with your personal vet in case of any queries.

Can Mirtazapine be given with other medications?

Transdermal Mirtazapine should not be given alongside monoamine oxidase inhibitors 14 days before or after treatment; otherwise, there are no other restricted medications for use with transdermal Mirtazapine. If you have any questions about the prescription, consult with your vet since they are in the best place to explain about your cat’s health.


Mirtazapine is an excellent antidepressant and appetite stimulant for cats. Once ingested, it results in weight gain that is associated with an increased intake of calories. The recommended starting dose is 1.88 mg daily in physiologically, nongeriatric normal cats. For elderly cats, especially those with liver disease, administer 1.88mg after every two days. Always stick to lower doses unless prescribed otherwise because of the reduced side effects. Transdermal administration of Mirtazapine is effective in ointment form because it guarantees the achievement of the required serum levels and weight gain.

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