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Other names | BW 306U; 6-Hydroxybupropion |
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Elimination half-life | 15–25 hours |
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Chemical and physical data | |
Formula | C13H18ClNO2 |
Molar mass | 255.74 g·mol−1 |
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Hydroxybupropion (code name BW 306U), or 6-hydroxybupropion, is the major active metabolite of the antidepressant and smoking cessation drug bupropion.[1] It is formed from bupropion by the liver enzyme CYP2B6 during first-pass metabolism.[1] With oral bupropion treatment, hydroxybupropion is present in plasma at area under the curve concentrations that are as many as 16 to 20 times greater than those of bupropion itself,[1][2] demonstrating extensive conversion of bupropion into hydroxybupropion in humans.[1] As such, hydroxybupropion is likely to play a very important role in the effects of oral bupropion, which could accurately be thought of as functioning largely as a prodrug to hydroxybupropion.[1]
Hydroxybupropion has two chiral centers and is a mixture of four possible enantiomers.[3][4][5] In humans however, presumably due to steric hindrance, only (2R,3R)-hydroxybupropion and (2S,3S)-hydroxybupropion are formed.[3][4][5]
Other metabolites of bupropion besides hydroxybupropion include threohydrobupropion and erythrohydrobupropion.[6][7]
The hydroxylation of bupropion to form hydroxybupropion occurs by cytochrome P450 2B6 (CYP2B6) oxidation (Faucette et al., 2000; Faucette, Hawke, Shord, Lecluyse, & Lindley, 2001; Hesse et al., 2000), and the subsequent cyclization results in the creation of a second chiral center with the potential for the generation of two diastereomers (Suckow, Zhang, & Cooper, 1997). Interestingly, only the trans-diastereomers, (2S,3S)- and (2R,3R)-hydroxybupropion (2a and 2b, respectively), have been found in plasma in humans and when synthesized de novo (Fang et al., 2000), indicating that they are the thermodynamically more stable isomers. Steric hindrance greatly reduces cyclization to the cis-diastereomers, (2R,3S)- and (2S,3R)-hydroxybupropion (Suckow et al., 1997). The chirality of the second stereocenters is determined by the configuration of the existing stereocenter alpha to the ketone derived from either (S)- or (R)- bupropion.
As hydroxybupropion has two chiral centers, there are four possible enantiomers. However, only (R,R)-hydroxybupropion and (S,S)-hydroxybupropion are found in human plasma [62].
Bupropion is chiral and CYP2B6 stereoselective metabolism is observed with (S)-bupropion being metabolised at more than three times the rate of (R)-bupropion (Coles and Kharasch 2008). Because hydroxybupropion has two chiral centres, four enantiomers should be observed: however, only (R,R)-hydroxybupropion and (S,S)- hydroxybupropion are found (Coles and Kharasch 2008).
Jefferson_2005
was invoked but never defined (see the help page).