I quit about 6 months ago, I'm 53 and have been smoking since I was 13 , my sister is a doctor and she gave me a prescription for Bupropion (same as Wellbutrin, Zyban). I took them for two weeks, then quit the cigs and took them for another two weeks after quitting.
Haven't had a cigarette since and haven't even missed them
Bupropion, Wellbutrin or Zyban are antidepressants and they apparently modify the dopomene levels.
http://en.wikipedia.org/wiki/Bupropion