We have a couple of excellent experts on the expert forum who can give you some sound advice on the medications available, as well as diet.
I've heard that some of the digestive enzyme supplements can be very helpful in aiding with IBS, as well.
I'm sure some of the others here who've had this problem can tell you some of the things they've tried as well.
When I had a Siamese that had this issue, the only thing my vet gave me to give to her was the steroid medication, Prednisone. He also gave her Reglan from time to time. I believe the vet had tried Flagyl a couple of times, too.
I would ask the vet if Prednisone or Prednisolone will help. Only, make sure kitty has nausea medication, too. I've taken Prednisone myself, so I know it can cause nausea.
When I had a sick Siamese with Colitis, that was nearly 10 years ago, so hopefully vet medicine has advanced since then.
I'm sorry your kitty has IBD. I remember what my Siamese went through. After a long illness, I finally had to put her down. It was clear that she had been suffering more than even I was aware of. She was such a beloved and sweet but shy little beauty. It broke my heart that I had to put her to sleep, but I knew it was the right thing to do when I did it. I knew I would beat myself up with a lot of guilt if I hadn't have done it when I did. I didn't want to part with my beloved cat, but I knew I had to let her go.
So sorry to hear your kitty is going through such tough times. I am the owner of an IBD cat, just like yours. The above is correct, prednisone helps with inflammation, but if used long term it can lead to diabetes. So you will end up with an IBD, diabetic cat. My kitty started to show symptoms at the early age of 3 months. I kept changing his diet and nothing worked. When I finally got the diagnosis from the vet I was very sad, because IBD causes a cat to live in misery, shorter life spam, and it leads to cancer eventually. You will eventually realize that antibiotics and everything else is just a temporary fix, which is exactly what you don’t want. IBD is food allergies. So, it can be fixed with food. And, that is the cure: Food. For the most part, prescription diets do not work but some owners claim that Hill Z/D is good. It did nothing but make it all worse in my case.
When I switched my Abby to raw foods, his IBD symptoms went away quite literally over night. Please read this lady’s story and let me know if you see yourself in her shoes. She found the cure to her IBD cat as well, and it has been over 7 years since the IBD symptoms have not come back. These websites will help you rid your cat from the pain.