How long before tapazole (methimazole) kicks in?

About 4-6 weeks. Tapazole(methimazole) has a slow onset of action. With initiation/change of dose, it may take ~4-6 weeks before symptomatic improvement is noticed (thus other therapies are used with tapazole for initial symptomatic relief). Depending on patient variables complete response could be achieved in 2- 4 months.Keep scheduled visits with your doctor for monitoring. Report any unresolved skin rashes.