He immediately started with the common side effects
(panting, excessive thirst, eating everything he could fit in
his mouth, etc.), but our real concern came when he started to collapse out of nowhere almost a week after starting the medication. We weren't sure what was wrong, and it took two more trips to the vet to find out that he was becoming severely anemic very rapidly. It turned out that his stomach had ulcerated, another side effect of the prednisone.