Bupropion is the active ingredient in Zyban. It was originally marketed as an anti-depressant and for this reason it is absolutely essential that you go to your doctor to have Zyban prescribed. There is evidence of it helping smoking cessation but in some cases it is medically inappropriate.
We are not medical practitioners so cannot tell you more than this, and we're sorry if this doesn't seem very helpful. Speak to your doctor, and make a decision if it's right for you based on his or her medical advice.
For further ideas and advice and ways to stop smoking, visit the substantial resources section of this site - Stop Smoking Resources