There's an increased risk of seizure as a result of taking Zyban, so people with seizure disorders, serious head trauma, or current or past eating disorders (anorexia and bulimia) should not use Zyban.
Additionally, bupropion should not be used in people who are already taking another form of bupropion, such as Wellbutrin, or who have taken an MAOI inhibitor antidepressant (such as Marplan, Nardil, Emsam, and Parnate) within the past 14 days.
Medical review: Nathan Cobb, MD, September 26, 2017
Fiore MC, Jaén CR, Baker TB, et al. Treating Tobacco Use and Dependence: 2008 Update. Clinical Practice Guideline. Rockville, MD: U.S. Department of Health and Human Services. Public Health Service. May 2008.