Mirtazapine For Cats: Overview, Dosage & Side Effects

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Mirtazapine is a prescription appetite stimulant commonly used in veterinary medicine for cats to encourage interest in food, eating, and to encourage weight gain.

Brands include Remeron and Mirataz. In this article, you’ll learn what mirtazapine is, how it works, different dosage forms available, potential side effects to monitor for, and some commonly asked questions.

Mirtazapine For Cats Overview

Medication Type:
5-HT3 (Serotonin) Receptor antagonist and tetracyclic antidepressent
Form:
Oral tablets, topical transdermal ointment
Prescription Required?:
Yes
FDA Approved?:
On the topical transdermal ointment Mirataz is FDA approved for use in cats.
Life Stage:
Mirataz safety studies in cats included cats as young as 7-10 months of age.
Brand Names:
Mirataz, Remeron
Common Names:
Mirtazapine
Available Dosages:
Mirataz Transdermal Ointment: 100mg/tube in a 5g tube (20mg/gram); oral tablets: 7.5mg, 15mg, 30mg, and 45mg.

About Mirtazapine For Cats

Mirtazapine is classified as a serotonin receptor antagonist and a tetracyclic antidepressant. However, in cats it is not used as a behavioral medication, but more for its benefits for encouraging appetite and eating.

Norepinephrine (NE) is a neurotransmitter which, among many other roles, does act at certain receptors in the body to increase appetite. Mirtazapine is thought to block receptors that would stop NE’s release. This leads to an increase in NE, and a subsequent increase in appetite.

Mirtazapine also blocks serotonin receptors. By blocking certain serotonin receptors, mirtazapine also provides an antinausea and antiemetic (anti-vomiting) effect.

Currently, mirtazapine is available commercially as a generic tablet, as well as the topical transdermal brand Mirataz, which is applied to the skin of the inner surface of the ear flap. 

What Does Mirtazapine Do For Cats?

Mirtazapine has been used for many years by veterinarians to aid in stimulation of appetite for cats. This may apply to cats with poor appetites, such as kitties with chronic kidney disease (CKD), or cats with other conditions causing weight loss where we want to encourage more calorie intake. 

Side Effects Of Mirtazapine For Cats

Mirtazapine can cause hypersalivation (drooling) and sedation (excessive sleepiness) in cats.

Mirtazapine is a generally well-tolerated medication in cats, but there are some adverse effects to be aware of and monitor for. 

Because mirtazapine does also act as a histamine blocker, sedation may be noted, especially at higher doses. 

The next most common side effect is increased vocalization, seen in about 50% of cats. Agitation and gastrointestinal effects like vomiting may be seen in about 25% to 33% of cats.

Abnormal walking, restlessness/hyperactivity, and hypersalivation (drooling) may be seen in just over 10% of cats. Remaining side effects, which affect just about 10% or less of cats, may include increased breathing and heart rate, poor appetite, disorientation, inappropriate elimination, tremors/shaking, and hiding behavior, among others. 

Studies looking at mirtazapine use in cats have noted fewer adverse effects when lower doses are used. 

For the topical brand Mirataz specifically, about 10% of cats may experience reactions at the site of application on the inner surface of the ear pinna. This can include but is not limited to redness, crusting, scabbing, and residue build-up. 

Of reports to the ASPCA Animal Poison Control Center, the most common signs seen in the event of an overdose included excessive vocalizing, agitation, and vomiting. Fortunately, at least in humans, doses upwards of 10 to 30 times the prescribed dose exhibited minimal toxicity, requiring only several hours of observation.

Mirtazapine can interact with a variety of different medications, especially sedatives, pain medications, and medications used to modify behavior. Always make sure to discuss any medications your kitty may be taking with your veterinarian if mirtazapine use is being recommended or prescribed.

Mirtazapine should be used carefully in pets with kidney disease, liver disease, heart disease, or diabetes mellitus. Mirtazpine is used commonly with some of these conditions lending to their impact on appetite, but doses may need to be lower and more carefully monitored.

If you are ever concerned that your kitty may have developed side effects while using mirtazapine, make sure to contact your veterinarian, the ASPCA Animal Poison Control Center (1-888-426-4435), or Pet Poison Helpline (1-855-764-7661) for further advice. 

Mirtazapine For Cats Dosage

Your veterinarian will recommend the ideal dosage and dosing frequency based on your cat’s individual needs.

The dose for the tablet form of mirtazapine may range from about 2 milligrams up to 3.75 milligrams, depending on goals and tolerance of side effects. The generic tablets only come in two sizes of 7.5 milligrams and 15 milligrams. 

Dosing frequency for the oral tablets may only be required once every 48 to 72 hours, but a cat’s appetite should be carefully monitored to determine the best dosing interval.

As the proper dose and frequency may depend greatly on your cat’s needs and any current health conditions, always make sure to discuss mirtazapine dosing for your kitty with your veterinarian first, including current and past health conditions.

The topical product Mirataz, which is a mirtazapine transdermal ointment FDA approved to manage weight loss in cats, has a labeled dose of a 1.5-inch ribbon of the ointment applied to the inner pinna (flap) of the ear once every 24 hours for 14 days. This equates to a dose of about 2 milligrams. 

With Mirataz, it is extremely important for the person applying the product to wear gloves to prevent absorption of the product on their own skin. Proper application of the product to the inner surface of the ear pinna is best done using a thumb or forefinger, but as a transdermal product, the medication could be absorbed through the skin of the person applying the product.

Although mirtazapine is also a medication sometimes used in people, accidental absorption of the product should still be avoided. 

Conclusion

Mirtazapine can be a great medication to help support kitties suffering from weight loss or a poor appetite. The topical brand Mirataz can also provide a welcome route of dosing a medication to a kitty already not eating well or difficult to give oral medication to. 

Mirtazapine can exhibit some side effects due to its activity as an antidepressant. However, in a majority of cats, especially those given lower doses, mirtazapine is often well-tolerated and a very useful therapeutic medication. 

Frequently Asked Questions

What does mirtazapine do for cats?

Mirtazapine is a type of appetite stimulant medication. It is most often used in cats suffering from a short-term or long-term decrease in appetite, as well as weight loss.

How long does mirtazapine last in cats?

This generally depends on the dose and form. An oral tablet dose may last on average for about 48 hours, though in some cats it may last for less time and closer to 24 hours, while for others it may last up to 72 hours. 

Does mirtazapine make cats sleepy?

Because one of mirtazapine’s actions is to act as a histamine blocker, it can lead to sedative effects. This is a similar effect as other medications we think of more as antihistamines for allergies, like Benadryl. This effect of mirtazapine is often seen more when higher doses are used, such as doses closer to 3.75 milligrams or higher. 

How much mirtazapine can you give a cat?

The labeled dose for the topical product Mirataz is a 1.5-inch ribbon of ointment applied to the skin of the inner pinna (flap) of the ear. This dose equates to 2 milligrams of medication.

The mirtazapine tablet doses may range from about 2 milligrams up to 3.75 milligrams commonly in cats, anywhere from every 24 to every 72 hours. Which dose is appropriate for your cat depends greatly on the condition causing poor appetite and/or weight loss, and other conditions your kitty may have.

Higher doses and increased frequency can be associated with more side effects, so it’s always extremely important to discuss dosing and frequency of mirtazapine with your vet prior to giving a dose to your cat.

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About Dr. Chris Vanderhoof, DVM, MPH

Dr. Chris Vanderhoof is a 2013 graduate of the Virginia-Maryland College of Veterinary Medicine (VMCVM) at Virginia Tech, where he also earned a Masters in Public Health. He completed a rotating internship with Red Bank Veterinary Hospital in New Jersey and now works as a general practitioner in the Washington D.C. area. Dr. Vanderhoof is also a copywriter specializing in the animal health field and founder of Paramount Animal Health Writing Solutions, which can be found at www.animalhealthcopywriter.com. Dr. Vanderhoof lives in the Northern Virginia area with his family, including 3 cats.

10 thoughts on “Mirtazapine For Cats: Overview, Dosage & Side Effects

  1. Michael R. Redmon

    Hello There,
    I’ve got a Adult Maine Coon Cat that’s 14-yrs old. Just five months ago I noticed he wasn’t eating anything at all during the day.
    So I put put some solid Cat Food out for him, he either didn’t eat of it, or just a little at a time. As time when on, I begin to worry more about him. So I made an App. with my Vet, and told her the problem I was having. So my Vet gave me some Mira-
    taz (“mirtazapine Transdermal Ointment”) 5g. small tube. I’ put this on the back of my Cat’s back Upper Pinna of his Ear, once
    daily. To help him with his appetite. This (“Mirataz”) came with a package insert, and this drug finely worked. I was so gad about this. Ill give it to you again, I just
    love my “Cat”, I don’t know what I’d do without him.

    Reply
    1. Avatar photoKate Barrington

      So sorry to hear your kitty isn’t feeling well, Michael! I’ve used Mirataz with one of my cats and it seems to work well. Hope it does the same with your cat! My “solid cat food” I assume you mean pate? Some cats can be picky about texture, so you might consider trying a recipe with meaty bits and gravy or broth. My cat showed absolutely no desire to eat until I brought out a particularly smelly pouch of fish-based cat food. I’d recommend buying a few different types of cat food pouches to see if you can find one your kitty will eat. That paired with the Mirataz will hopefully help him gain his appetite back!

      Reply
  2. elle

    our cat has basically just stopped eating , has been given this stimulant by vet to have every 48 hours but its not helping.
    have bought many different foods but no luck. Blood tests say he is fine but a tad anemic . Not sure what else to try

    Reply
    1. Avatar photoDr. Chris Vanderhoof, DVM, MPH Post author

      Hi Elle,
      Sorry to hear about your kitty. There is another appetite stimulant that is approved for use in cats that you could ask your vet about called Elura (capromorelin). However, mirtazapine usually has at least some positive effect in many cases. If your cat is still not eating, further diagnostic testing may need to be considered to determine what the underlying cause of the anorexia is. Consider asking your vet about other testing options available including x-rays and ultrasound, if these haven’t come up yet. Other supportive care medications beyond just appetite stimulants may also be needed, depending on the underlying issue that is affecting appetite.

      Reply
      1. elle

        Thank you for the reply.

        The vet has redone bloods, x-rayed and parasite test to no avail.
        Cat has taken to licking my chiminea, we are wondering if the loss of our other 3 pets
        this year due to old age and cancers and the introduction of a new puppy may be his issue

        Reply
  3. Rudy

    My cat started severe bleeding from the eyes after getting the ribbon of Mirataz on the inner pena of the ear. Did not see a specific warning for this. My cat has not eaten any wet Pate cat food or dry food, and has been losing weight. Be careful using. I hope no one else has this problem. My 11 year old cat also has kidneys which are in decline. Poor kitty.

    Reply
    1. Avatar photoDr. Chris Vanderhoof, DVM, MPH Post author

      Hi Rudy, this is an unusual thing to see happen and has not been reported with mirtazapine use in any studies to my knowledge, even in the list of very rare effects. I was not clear if this is bleeding within the eyes that took place or if it was actual blood being seen on the face thought to originate from the eyes. Either way, something like this is more likely to be occurring because of another underlying condition, such as hypertension in the case of bleeding within the eyes (which could be seen associated with kidney disease), or a blood/clotting disorder in the case of the latter. I would generally be more concerned that an underlying cause of your kitty’s poor appetite and weight loss would be responsible (which could be kidney disease depending on how advanced it is vs. an additional condition) vs. the mirtazapine alone.

      Reply
  4. C Edge

    Test for histoplasmosis. My cat had these symptoms of decreased appetite, lethargy, looking disheveled, weight loss, anemia, inflammation in the blood work. They kept trying to diagnose him with cancer and wasted a lot of time and money…

    Reply
  5. Barbara Iskowitz

    What happens to Mirataz after 30 days? The pkg says to disgard after 30 days. My vet told me that I could use it on an as-needed basis and it does work for a few days after one dose. Does Mirataz lose effectiveness or something more serious. My cat will be 19 in April and has some kidney disease. Thank you.

    Reply
    1. Avatar photoDr. Chris Vanderhoof, DVM, MPH Post author

      Hi Barbara,
      This is a good question, but not one that there appears to be a simple answer for. The drug insert does not contain any supportive info on why Mirataz should be discarded after 30 days. My best guess would be that either the drug or the ointment carrier lose their stability and effectiveness after 30 days of the package being opened and exposure. It may be possible that the drug is simply less effective at being absorbed properly after that time.

      Reply

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