Thanks for your question.
Chantix is a drug used to help minimize withdrawal symptoms of nicotine cessation. Be sure to follow the specified directions on timing of the medication and stopping the tobacco.
It would be improper for me to suggest that it would be safe to take the Chantix when it has past its expiration date. The smartest thing to do is obtain a new prescription from the pharmacy (or your doctor). I will say that most drugs don't go "bad" at the expiration date. They may lose potency over time, but rarely cause a problem, especially in the first year. Some drugs however, do go through a chemical change which can be harmful, such as Aspirin.
So, when in doubt, get another prescription. The safest thing to do is to take no chances.
Congratulations on this important decision to stop smoking.
Martin Cane, M.D.