What are the side effects of stopping pro gout tablets?

Maybe a gout attack: I assume you were taking the tablet because you had gout before? If so, stopping it will risk getting recurring attack(s) which tends to worsen with each subsequent episode and may/likely cause joint damage/gouty arthropathy (arthritis due to gout). So, check with doc before stopping it. If you have side effect from it, there maybe other options. Consult doc. Good luck.

Gout Flare: I assume that you mean Allopurinol or uloric. When you stop your medicine, the serum uric acid level suddenly goes up which can trigger a painful gout attack. In general once you start this medication, you are on long term. It not only helps prevent gout attacks but also helps prevent joint damage from gout.