Bupropion (Aplenzin, Wellbutrin, Wellbutrin SR, Wellbutrin XL) is used to treat depression. Bupropion (Aplenzin, Wellbutrin XL) is also used to treat seasonal affective disorder (SAD; episodes of depression that occur at the same time each year usually in the fall and winter but rarely may occur in the spring or summer months). Bupropion (Zyban) is used to help people stop smoking. Bupropion is in a class of medications called antidepressants. It works by increasing certain types of activity in the brain.