call the pharmacy where you had the prescription filled or check the packaging. you should be able to find an expiration date. as long as the product is still in the date range it should be safe to take. but you need to start at the correct dosage. check with your doctor or pharmacist to be sure you have what you need to follow the correct regimen.
i took chantix for a couple of weeks and then stopped. can i use my old pack from a couple of months ago?