Zyban is the GlaxoSmithKline tradename of a bupropion hydrochloride (amfebutamone, Wellbutrin) sustained release tablet. The drug is sold to help people stop smoking tobacco by reducing the severity of withdrawal symptoms. It can be used in combination with nicotine replacement therapies.

Bupropion is a tricyclic aminoketone antidepressant and is marketed as the antidepressant Wellbutrin, the sustained release effect was added to create Zyban. Its pathway of effect has not be clearly identified but it is believed to be a monoamine uptake inhibitor, but also has some effect on the dopamine transporter and on norepinephrine uptake. The efficacy over placeboes has been proved in clinical trials with bupropion resulting in a two- or three-fold improvement in abstinence rates.

It has a number of common side effects, including dry mouth, dizziness and insomnia. Possible side effects are shakiness, skin rash, anxiety, nausea, rhinitis, constipation, and breathing difficulties. Other side effects are possible, including a very low chance of seizures. An allergic reaction is possible. An overdose is more likely to induce seizures and also tachycardia.

It is contraindicated in people taking medication for seizure disorders (dilantin, phenobarbital), with bulimia or anorexia, with kidney or liver disfunctions, or people already taking Wellbutrin, Bupropion HCL, or any monoamine oxidase inhibitor. It can also cause problems with cold remedies, certain herbal supplements, creatine, cimetidine, ephedrine, and Valium-like medications

A Zyban treatment course lasts for seven to twelve weeks at 300 mg/day with the patient halting the use of tobacco around ten days into the course.