Bupropion is an antidepressant medication. The exact way that bupropion works is unknown. Bupropion is used to relieve symptoms of depression such as feelings of sadness, worthlessness or guilt, loss of interest in daily activities, changes in appetite, tiredness, sleeping too much, insomnia, and thoughts of death or suicide. Bupropion is also used to help people stop smoking by reducing withdrawal effects. Bupropion (amfebutamone) is an antidepressant of the aminoketone class, chemically unrelated to tricyclics or SSRIs. It is similar in structure to the stimulant cathinone, and to phenethylamines in general.
Bupropion is a selective catecholamine (norepinephrine and dopamine) reuptake inhibitor. It has only a small effect on serotonin reuptake. It does not inhibit MAO. The actual mechanism behind bupropion's action is not known, but it is thought to be due to the effects on dopaminergic and noradrenergic mechanisms.
Chemically, bupropion is related to phenylethylamines and has a relative molecular weight of 276.2. Although, bupropion was initially marketed as an anti-depressant (Wellbutrin), it is chemically unrelated to tricyclic, tetracyclic, selective serotonin reuptake inhibitors or other known anti-depressants.
The pharmacokinetics of bupropion is best described by a two-compartment model with a distribution phase (how long it takes for the drug to be absorbed into the body and begin working) having a mean half-life of 3-4 hours, and an elimination phase (how long it takes for it to be metabolised and broken down to inert waste products) which has a half-life of 21 hours. Bupropion is extensively metabolized into three active metabolites. At least one of these metabolites is formed by an enzyme called cytochrome P-450 2B6 enzyme. The terminal half-life of the three metabolites ranges from 21 to 37 hours. This means that it may interact with other drugs which also effect this enzyme, such as orphenadrine and cyclophosphamide. The main known side-effects of zyban are dry mouth and dizziness, although there are a few others.