Socks is having pancreatitis, and had similar symptoms.
If the cat is not drinking water either, the immediate danger is dehydration, which can also lead to loss of appetite. The quick solution for that is Sub-cutaneous (sub-q) fluids to maintain hydration. In one case, Socks returned to normal eating just with 200ml sub-q. Now we have learned to do sub-q at home, as the situation came back again and again. Usually we only need to do it once or twice (100-150ml) in each situation (after he vomited).
After that, a kind of steroid (prednisone?) was fed for several weeks. Usually after one or two pills, the cat will start to eat. Then the problem is how to control the strong appetite. That's what we are facing right now. Socks now is like a bottomless hole for food, however if we fed him too much he will puke. The steroid cannot be stopped immediately once started even if the symptoms got relieved, it has to be reduced gratuately over several weeks.
Antibiotics was also used for a while, but I dont know if that really make sense, since this is not a bacteria infection, I just followed vet's instruction since he said the experience has showed some positive effects of antibiotics. We also gave him some anti-vomiting med because vomiting was also a big problem for socks and he could lost water very quickly from vomiting.
See treaments in this link:
http://www.felineoutreach.org/Education/Pancreas.html
