Any side effects to antithyroid medication?

Multiple but uncommon: One in ten patient on antithyroid drugs can have rashes, joint pains, bad taste in their mouth. More rarely, patients may have a reversible drop in their white blood cells. This is a dangerous but rare side effect that can lead to severe infection. Even more rarely, liver disease can occur, and an inflammation of the blood vessels called vasculitis. Your doctor should explain all this carefully so taht you can recognize side effects timely.