My vet loves Cerenia, for some reason. I have given J.D. the tablets that you have to split into quarters (that wasn't easy). I think it has some anti-inflamatory for the gut or maybe it's a pain killer (I'm sorry, I don't remember) in it, that Ondansetron does not. I give J.D.'s insulin in his sides, so when I give him an injection of another med., I give it in his scruff. I just did some Googling and it looks like Cerenia should be used with caution if liver or some heart problems are present. If you choose to go with Ondansetron, Costco Pharmacy has the best (by far) price.