Jayla-n-Drevon, may I ask how you got him eating again before you started the prednisone? Or did you not really? Also did you do the endoscopy? Thanks. this is all very helpful.
I make a gel cap cocktail 2x a day with ondansetron 2-3 mg (he is now 14.5 pounds he was 12.5)
If he needs ondnsetron more I give as it only lasts about 6 hours give or take...
Let me give you a little history-
Rico has never had "normal" poo--but it was ok- we have had tests etc with no findings.
He broke a tooth and had a dental last May I believe-this seemed to cause worse water poo and his appetite has always been finicky-
he has weighed 11.5-12.5 most of his life.
I went to a cat specialist and they could tell me what it was NOT--

(so could the cable guy)

the water (and I mean water) poo didnt seem to hurt his bottom or his other activities-but was becoming more frequent-the smell was horrendous (still is)
we tested for EPI (negative)-did a extremely complete blood and poo panel with no results.
He has been on sq for 6 years -not anymore so it is a fine balance wit lasix-
No endoscopy because I refused to sedate him as he did not do well with dental sedation and he is a senior-
After the specialist my regular vet and I agreed clinically it looked like IBD-Lymphoma
Upped the pred dose to 5 mg 2x a day...within 3 days he had normal poo-within 6 days he was in ER not able to breathe-
Cardio agrees IBD or lymphoma and put him on budesonide while weaning off pred.
They gave him 3 weeks and that was at least 3 months ago-
To specifically answer you... He does well on mitrz but I feel it increased heart rate-so we stick with cypro and I am pro active about not waiting until "he needs it" because it is hard to catch-(we have kidneys involved too)
I do have another pro biotic I am going to try --I tried it 1x but I think I gave too much as he puked over and over-
He tolerated the others but did not help the water poo.
he also eats ff turkey and giblets (as well as many other kinds and brands)
sorry to blubber!

I did just have conversation with a lady whose cat respond amazing to budesonidee ( I personally think it also retains a little fluid)