Buproprion is an inhibitor of the reuptake of dopamine and norepinephrine and is also an antagonist of neuronal acetylcholine nicotinic receptors. Because of its effects on nicotinic receptors, it is used to promote smoking cessation. Hydroxy bupropion is a mixture of enantiomers produced by the metabolism of buproprion by cytochrome P450 2B6. Compared with buproprion, this racemic mixture produces equal inhibition of norepinephrine reuptake (IC50 = 1.7 µM) and much weaker inhibition of dopamine reuptake (IC50 >10 µM). Moreover, hydroxyl bupropion isomers are potent antagonists of nicotinic receptors, suggesting that they may substitute for bupropion in smoking cessation.