File:Metabolism of bupropion in humans.jpg

"FIGURE 10 Main metabolic pathways of bupropion. CR, carbonyl reductase; CYP, cytochrome P 450"

Description from the source:

"The biotransformation of [bupropion] is mediated principally by CYP2B6, producing hydroxy[bupropion] (which can then undergo spontaneous cyclization to the corresponding hemiketals, Figure 10B,C); reduction of the carbonyl group to alcohol by carbonyl reductases generates erythrohydro[bupropion] (Figure 10D) and threohydro[bupropion] (Figure 10E).268 These metabolites are active, and threohydro[bupropion] and (R)‐hydroxy[bupropion] reach plasma levels much higher than those of the parent drug, thus they are supposed to contribute significantly to the overall therapeutic effect.269 Recently, three new metabolites have been discovered: 4′‐hydroxy[bupropion] (Figure 10F), and the respective erythro‐ and threo‐ 4′‐hydroxyhydro[bupropion] (Figure 10G,H); together, these metabolites are excreted in amounts similar to those of all the previously known metabolites.270"

Source:

• (September 2020). "New-generation, non-SSRI antidepressants: Drug-drug interactions and therapeutic drug monitoring. Part 2: NaSSAs, NRIs, SNDRIs, MASSAs, NDRIs, and others". Med Res Rev 40 (5): 1794–1832. DOI:10.1002/med.21671. PMID 32285503.