My cat with intestinal cancer eats Hills Perscription Diet W/D. (So does the diabetic cat... and everyone else in the house... and they are so much healthier for it. Lost weight to a normal weight, softer fur, and they don't eat as much as they used to when they ate junk because the protein content is much higher.)

Because of the cancer, he would puke a lot, but between the food and his laxatives, that stops to maybe once every other day or so.

Laxatives also help the hairballs pass through. Might be an idea. He's taking something called lactulose that is a human Rx med.