Mirtazapine and constipation

This question has been lingering in my head for a while.

Poppy has constipational issues. Around the Fourth of July holiday she also started exhibiting appetite issues which turned out to be IBD. At the time we didn't know it, though, and she didn't have any of the usual vomitting and diarrhea associated with IBD. We took her to a vet and wound up getting a dose of Mirtazapine.

I was a bit worried because one of the side effects of Mirtazapine is supposed to be constipation. But instead she had 4 bowel movements the next day, and after that one movement a day until the MIrtazapine wore off.

Poppy is normally a bit high strung, and Mirtazapine has anti-depressant qualities. She became rather friendly, more outgoing. Since constipation can occur due to stress, I'm wondering if that was why she had all the bowel movements. Or does someone else have a possible explanation?

Note that Poppy is doing better now, so I am mainly asking so I can tell her vet later this month and possibly fill in more parts of the puzzle as to her constipational issues, but I am not particularly worried about it at this point.

I wish I had an answer for you, but I don't.  Hoping this will bump your question up for someone else to see who is more experienced with this.

Mirtazapine is actually an andi-depressant for humans.  It's use as an appetite stimulate in cats is off label use.  They are basically using the side effect of the medicine which is increased appetite.  My cat also has IBD with constipation rather than the more common diarrhea.  He will go more for a period of time and then go less for a period of time.  My vet has told me that he can be give Miralax even daily if needed.  He is also on a steroid but hopefully it won't come to that for your cat.  He hasn't been given anything as an appetite stimulant.

Patches did also have vomiting bile along with the anorexia and constipation.

I think it's more a matter of his eating better while on the medication than being a side effect of the medicine.