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Dr. Deb
Dr. Deb, Cat Veterinarian
Category: Cat Veterinary
Satisfied Customers: 10268
Experience:  I have been a practicing veterinarian for over 30 years.
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This is another question about mirtazapine; my 6 month old

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This is another question about mirtazapine; my 6 month old kitten Sylvia got spayed last Tuesday and has not done well since then--very subdued and appetite went from so-so to extremely poor over the weekend. I took her to my regular vet this morning and her weight was down 9 oz from Tuesday--she currently weighs 5 lbs 2 oz. She has moved her bowels normally since surgery (last known BM Saturday night, evidence suggests she had another Sunday night) and has not had any vomiting, is not lethargic, and has been drinking water, though vet found her to be dehydrated. Labs are OK, FLV/FIV test was negative, no fever, no incisional inflammation or tenderness. She got a fluid bolus and an antiemetic (Cerenia) and vet started her on mirtazapine, 1/4 of 15 mg tab every 3 days; I gave her first dose this afternoon around 1PM.

1) can I expect her to be feeling the effects by dinner time (5PM)? I offered her some tuna around 2 but she wasn't interested--May have been too soon.

2) is the dosing OK for a 5 lb cat?

3) I trust my vet and feel she did a thorough assessment, but is Sylvia's condition suggestive of anything to you? I thought she may have developed a partial ileus but that doesn't appear to be the case.

She is passing gas too, by the way.

Hi, I'm Dr. Deb.
I recently came online and see that your questions about Sylvia haven't been answered. I'm sorry that you've had to wait for a response but if you still need assistance, I'd like to help if I can.

1. Mirtazapine doesn't help stimulate the appetite in every cat but if it's going to work, I've found that it can sometimes take up to 12 hours or so before it does.
Cyproheptadine is another drug which can also be used as an appetite stimulant although Cerenia also has this property in addition to being an anti-emetic.

2. The dose of Mirtazapine is correct: 3.75 mg/cat every 72 hours although it can also be given as 1/8th of a 15 mg tablet every day.

3. If blood work post-spay was normal and there's no evidence that her surgery was compromised in any way (post-op infection, for example), then her symptoms are not specific for one particular condition. When faced with these situations, I have to suspect that the patient is possibly having a longer than expected drug reaction or possibly the stress of the surgery has triggered some underlying condition which was dormant.
If the former, then with symptomatic treatment (fluids and appetite stimulants), she should recover.
But if the latter, it may not be immediately obvious what the problem might be but examples include:
FIP (Feline Infectious Peritonitis) can be triggered by a stressful event. Usually those cats are running fevers in addition to not eating and being lethargic, though.
Inflammatory Bowel Disease is another condition which might be exacerbated by stress; often diarrhea is seen with this condition; gas would fit, too.
Pancreatitis can cause inappetance although she is a little on the young side for this condition.

Since all of her lab work is normal and her incision site looks good and there's no evidence that this is specifically related to the surgery itself, I would continue to treat her symptomatically for a few more days to see if she'll start eating again.

I hope this helps and that she recovers quickly with treatment; I'm certain that this is your fervent wish as well!
Again, my apologies for the delayed response to you. Deb

Customer: replied 3 years ago.

Thank you! She didn't eat well at dinner but she did eat, which is a vast improvement over not eating at all, so I am encouraged. Funny you should mention IBS-- as a tiny kitten she had uncontrollable, blood-tinged mucoid diarrhea and I did wonder about IBS but she was much too young for it and in any event it resolved once she was weaned from the bottle. She got tested for every parasite under the sun in the meantime! Thanks again--she is special to me since she is a bottle baby and I appreciate your thorough answer.

You're more than welcome.

I agree that IBS (or IBD) would be quite uncommon in a very young kitten; usually internal parasites are going to cause loose stools. But fecal samples can be falsely negative since eggs are not shed in every stool sample so I always treat these babies for parasites if the problem persists.

Even though 6 months is a little on the young side for IBS, I've seen it on occasion, so I wouldn't entirely rule it out....or a reaction to the ingredients of the food (which is usually related to IBS in one way or another).

But the fact that she seems to be responding and ate at least something at dinner is quite encouraging. Hopefully, she just needs a little more time to get past this.

I know how special those bottle-babies are:)

Please keep me posted about her if you would. Even after you've rated (if you do, of course), we can still continue to communicate at no additional charge to you.
I can also send you a follow-up email in a few days.

Good luck:) Deb

Dr. Deb and other Cat Veterinary Specialists are ready to help you
I'm just following up on our conversation about Sylvia. Has her appetite returned? Deb