I'm so sorry that Spike got this terrible disease. I am wondering how much peroxicam he is getting, at what time, and is he getting anything else? Reason being, Kacee my Scottie got 3.5 ml (liquid) - I would feed her then wait about and hour then give her pepcid then about 30 minutes after that she would get her peroxicam. In the beginning she had similar symptoms, so I had to lower the peroxicam dosage and gradually work back up.
Every dog is different so it is trial and error to find what will work best with your baby. There are also alot of holistic formulas which have helped many on this board. If you go to page 2 of the pet cancer board there is a posting that says "link to more messages...." On that link you will find over 600 posts that will give you alot of information and support. In the mean time, love Spike every single day you have him. Stay up beat. They don't know they are sick - and we don't want to tell them. Good Luck
Karen