Mirtazapine side effects - when to worry?

Previous post in Lantus forum: https://www.felinediabetes.com/FDMB/threads/3-22-falafel-amps-278-2-25-299-5-174-6-176.287987/

Took Falafel to the vet yesterday and they gave us Cerenia and Mirtazapine to help with her appetite. This morning i gave her 3.75mg of Mirtazapine as directed since last night she didn't eat much.

She is restless (going back and forth between two rooms in the house) and vocalizing A LOT. I called the emergency vet and they said they would have given a smaller dose, 1.88mg, instead.

I did some research and I saw that the nickname for this medicine is MEOWzapine but I'm still scared and nervous. Knowing none of you are advising me in a veterinary capacity, when should I worry? Her walk is fine, she's not drooling, and she's eating (but tbh I expected more of an effect on her appetite, we're still working on 1 can of food so far). I'm so unnerved by the vocalizing.

 

Yes, I had a cat that took Mirtazapine. No less than 20 minutes later he would start vocalizing a lot. Every time. Pretty sure the meowing will be just fine. I am glad she has started to eat.

 

I ja using the transdermal Mirtazapine and sometimes my civi Cookie vocalizing.
I agree with reducing the dose to 1.88 g (1/8 of 15mg tab). I suspect the frequency of the 3.75 mg was every 3 days. The frequency for the 1/88 g dose shouod be once every 2 days.
https://todaysveterinarypractice.com/pharmacology/mirtazapine-addressing-appetite-in-cats/

 

Thanks @Shell @Larry and Kitties ! It was my first time so got super nervous. She has calmed down a bit!

 

That’s right! Meowtazapine.

Don’t worry. If you have Cyproheptadine at home you can give that as it will reverse the effects pf the Mirtazapine. That reaction isn’t uncommon. That dose is just too much for your cat. Cut the dose in half (after these side effects has subsided) and try giving it every other day instead of daily. You can experiment with how much and how often. Most of my cats only use about half of a standard dose and only every other day and sometimes every third day, depending on the cat.

 

Okay I'll try the half dose on Tuesday! I wish the vet had warned me, the vet tech who gave me the medicine said to expect no side effects, the ones to watch out for were vomiting and having a weird gait so when she started meowing I really was worried she was trying to tell me she was uncomfortable, lol.

Did you have to regularly dose Darcy with the appetite stimulants? This is a separate question, but I'm unsure about when to pull out the Cerenia my vet gave me as well...

 

I have had sweet, mild- mannered kitties even become aggressive toward my other cats when given too much Mirtazapine…. smacking them around. I have used it with many cats over the years. Right now my heart kitty, Ginger, is on it.

As for the Cerenia, it’s a good idea to use it if your cat has a condition that causes nausea. If you give the appetite stimulant without something to help with nausea, it can cause food aversion— because the Mirt makes them hungry but they also feed sick. Is he currently on Clavamox? That itself could be causing a lot of GI problems (even though it’s a very effective antibiotic.)

 

So things to watch out for indicating nausea can be: walking up to the food bowl and sniffing food and then walking away, only licking off the top and then walking away, excessive lip licking, making strange sounds when eating — like tooth grinding.

 

Was he given the Cerenia for vomiting? It’s very effective at helping to control vomiting.

 

Usually there are no side effects with Cerenia at the doses used for for vomiting — occasionally some cats will seem slightly sedated and a few cats will drool a bit. I have only seen some drooling in a cat who was on it quite long term (a CKD kitty.)

How many mg. were you prescribed? How much does Falafel weigh?

 

Also, if you are not getting a boost in appetite, I would definitely give the Cerenia.

 

@Suzanne & Darcy Thanks for all the info!! Answers:

Falafel is on Clavamox for her UTI. We're on round 2 (a 2 week dose) bc just 1 week on the antibiotic wasn't enough to kick the UTI. The vets did a urinalysis and confirmed Clavamox should be working, but they're thinking that the diabetes is helping the UTI stick around longer so this is plan A before we go for more aggressive treatment.

Based on your post about nausea, that's interesting... out of all those signs, she was sniffing her food and walking away (up until Friday when we went to the vet). But, she would eat if I cuddled her and praised her. At my most effective, I could get her to eat about 1.5 cans (not ideal). Vet prescribed the Mirtazapine and Cerenia to use on an as-needed basis because she wanted her eating more. I gave the Mirtazapine yesterday morning and she ate 2 cans yesterday! Today so far we are halfway into can 2. I do smell ketones on her today so I'm glad the Mirtazapine is working, hoping I can get her to eat 2.5 cans. (I will try to get a urine ketone test but she's a tricky kitty. I ordered a blood meter today, and am getting the results of her updated labs tomorrow.)

Re: the Cerenia, the vet gave it to me more as a back up. Falafel has vomited twice recently (3/9 and 3/21) so it's not a chronic issue. Some other users suggested she might have acidity in her tummy in the early AM.

Weight is sitting at around 8 lbs, but her ideal weight is 10 lbs. We are slowly gaining since her DKA in late Feb. Here are all her prescriptions:
Clavamox: 62.5mg 2x a day
Cerenia: 4 mg (I need to cut the 16 mg pills up into 4ths before use)
Mirtazapine: 3.75 mg (but I will be reducing this to 1.8)

 

The Clavamox is probably not helping her appetite, but you just have to get through it if at all possible. That must be a nasty UTI! I would give Cerenia at closer to 1 mg per lb. so half a 16 mg tablet, but I guess you need to try what the vet said. The tablets are very bitter and can cause foaming at the mouth if she gets a taste of it. I always put my Cerenia into a size 4 or 5 empty gelatin capsule so that my cats can’t taste it.

 

I also have a blood ketone meter. It’s hard to always catch them in the litter box.

Glad she’s eating better. It can help to do all the encouragement to get them to eat. Holding the bowl can help too, but you probably already have been doing that! I hope she keeps improving.

 

The clear white/foamy (sometimes slightly yellow) fluid vomited early a.m. can be excess acid on an empty stomach, yes.

 

Okay, I have size 4 gel capsules! That’s interesting that my vet suggested a lower dose for Cerenia and higher for Mirzatapine (comparatively speaking). I think I will try Cerenia next before I do another dose of Mirzatapine.

 

That’s a great idea.

 

About the dose, your vet is probably just trying to start with the minimum effective dose. cerenia has a wide margin of safety. Some cats will do well on that smaller dose but some will need the half tablet. When Cerenia is used for motion sickness you give a much larger dose to prevent vomiting in cats with motion sickness. I think it’s always best to find the smallest effective dose. I hope your sweet girl will feel better soon.