Bupropion or bupropion hydrochloride, also known formerly as amfebutamone, is a medication primarily used as an antidepressant and smoking cessation aid. Marketed as Wellbutrin and other trade names, it is one of the most frequently prescribed antidepressants in the United States, although in many English-speaking countries, including the United Kingdom, Australia and New Zealand, this is an off-label use. It is also widely used, as the brandname Zyban, to aid people who are trying to quit smoking. Bupropion is taken in tablet form and is available only by prescription in most countries. Chemically, bupropion is in the aminoketone family.Bupropion serves as an atypical antidepressant different from most commonly prescribed antidepressants such as selective serotonin reuptake inhibitors (SSRIs). It is an effective antidepressant on its own, but is also popular as an add-on medication in cases of incomplete response to first-line SSRI antidepressants. In contrast to many other antidepressants, it does not cause weight gain or sexual dysfunction. The most important side effect is an increase in risk for epileptic seizures, which caused the drug to be withdrawn from the market for some time and then caused the recommended dosage to be reduced.Bupropion is known to affect several different biological targets, and its mechanism of action is only partly understood. It has been widely described in the literature as a weak norepinephrine-dopamine reuptake inhibitor (NDRI). However, this is not entirely accurate. There is evidence that bupropion induces the release of norepinephrine and dopamine in addition to inhibiting their reuptake, similarly to other cathinones like amfepramone (diethylpropion). Moreover, studies with humans via the oral administration route have demonstrated that bupropion does not significantly affect dopamine levels in the brain at clinically-used doses, indicating that its in vitro capacity to inhibit the reuptake and induce the release of dopamine is not involved in its clinical effects. This finding can be reasonably explained by extensive first-pass metabolism of bupropion into metabolites with differing pharmacology – namely, selective noradrenergic action without dopaminergic effect. In addition to its monoaminergic actions, bupropion and its metabolites act as non-competitive antagonists of several neuronal nicotinic acetylcholine receptors (nACh receptors), a property which appears to be importantly involved in both the antidepressant effects of bupropion and its efficacy in smoking cessation. Chemically, bupropion belongs to the class of aminoketones and is similar in structure to stimulants such as cathinone and amfepramone, and to phenethylamines in general.Bupropion was synthesized by Nariman Mehta and patented by Burroughs Wellcome in 1969, which later became part of what is now GlaxoSmithKline. It was first approved for clinical use in the United States in 1989. It was originally called by the generic name amfebutamone, before being renamed in 2000. Its chemical name is 3-chloro-N-tert-butyl-β-ketoamphetamine. It is a substituted cathinone (β-ketoamphetamine), and by extension, a substituted amphetamine.