Sporonox is patented. As such, no other company can make a generic version of it right now. It is supposedly to keep the price up to cover the cost of research for the original producer. I think patents run 5 years or something like that. Then, anyone can make a "generic" version, and the price gets competitive. Generic drugs are exactly the same as the drug that was patented -- and the FDA regulates both. Compounded drugs, like the itra version sold by Roadrunner Pharmacy, for example, are 99.9% the same (I am estimating). The point is they cannot be EXACTLY the same -- as that would violate the patent the originating company still has on the drug. What is the difference? Only the chemists that make it know. Most importantly, the FDA does not monitor or regulate compounded drugs in any way.
Comet took Sporonox even though it was horrendously expensive ($600/month or so). But, he was only on it for four months since he had a weak positive (and now tests negative ...which I will continue checking every couple months). Franklyl, after all the other bills for the tests and then the surgery to remove his eye, the drugs were the least of it, and we probably would have kept him on it. But, I would not feel badly about putting him on the compounded drug if we felt the other was just too much.
It is possible that the compounded version is making your dog sick. You could try another compounded version (there are at least two compounding pharmacies in Arizona) or go back to Sporonox.
Your vet sounds like the first three that Comet saw. Their ignorance was only exceeded by their arrogance. And the fact that they destroyed my dog's retrieving competition future and almost killed him makes me burn.