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Bupropion is used for treating depression, obesity, and seasonal affective disorder, and for smoking cessation. Bupropion is commonly prescribed, but has complex pharmacokinetics and interindividual variability in metabolism and bioactivation may influence therapeutic response, tolerability, and safety. Bupropion is extensively and stereoselectively metabolized, the metabolites are pharmacologically active, and allelic variation in cytochrome P450 (CYP) 2B6 affects clinical hydroxylation of single-dose bupropion. Genetic effects on stereoselective disposition of steady-state bupropion are not known. In this preplanned secondary analysis of a prospective, randomized, double-blinded, crossover study which compared brand and generic bupropion XL 300 mg drug products, we measured steady-state enantiomeric plasma and urine parent bupropion and primary and secondary metabolite concentrations. This investigation evaluated the influence of genetic polymorphisms in CYP2B6 , CYP2C19 , and P450 oxidoreductase on the disposition of Valeant Pharmaceuticals Wellbutrin brand bupropion in 67 participants with major depressive disorder. We found that hydroxylation of both bupropion enantiomers was lower in carriers of the CYP2B6*6 allele and in carriers of the CYP2B6 516G>T variant, with correspondingly greater bupropion and lesser hydroxybupropion plasma concentrations. Hydroxylation was 25-50% lower in CYP2B6*6 carriers and one-third to one-half less in 516T carriers. Hydroxylation of the bupropion enantiomers was comparably affected by CYP2B6 variants. CYP2C19 polymorphisms did not influence bupropion plasma concentrations or hydroxybupropion formation but did influence the minor pathway of 4'-hydroxylation of bupropion and primary metabolites. P450 oxidoreductase variants did not influence bupropion disposition. Results show that CYP2B6 genetic variants affect steady-state metabolism and bioactivation of Valeant brand bupropion, which may influence therapeutic outcomes. SIGNIFICANCE STATEMENT: Bupropion, used for depression, obesity, and smoking cessation, undergoes metabolic bioactivation, with incompletely elucidated interindividual variability. We evaluated cytochrome P450 (CYP) 2B6 , CYP2C19 and P450 oxidoreductase genetic variants and steady-state bupropion and metabolite enantiomers disposition. Both enantiomers hydroxylation was lower in CYP2B6*6 and CYP2B6 516G>T carriers, with greater bupropion and lesser hydroxybupropion plasma concentrations. CYP2C19 polymorphisms did not affect bupropion or hydroxybupropion but did influence minor 4'-hydroxylation of bupropion and primary metabolites. CYP2B6 variants affect steady-state bupropion bioactivation, which may influence therapeutic outcomes., (Copyright © 2024 by The American Society for Pharmacology and Experimental Therapeutics.)

Background and Aims: CYP2B6, a genetically variable enzyme, converts bupropion to its active metabolite hydroxybupropion. CYP2B6 activity and bupropion-aided cessation differ between women and men. The aim of this study was to determine whether genetically normal (versus reduced) CYP2B6 activity increases bupropion-aided cessation in African American smokers via higher hydroxybupropion concentration, and whether this differs by sex., Design and Setting: Secondary analysis of a smoking cessation clinical trial (NCT00666978)., Participants/cases: African American light smokers (≤ 10 cigarettes/day)., Interventions: Participants were treated with bupropion for 7 weeks., Measurements: Participants with detectable bupropion and/or hydroxybupropion concentrations were divided into normal (n = 64) and reduced (n = 109) CYP2B6 activity groups based on the presence of decreased-function CYP2B6*6 and CYP2B6*18 alleles. Biochemically verified smoking cessation was assessed at week 3, end of treatment (7 weeks) and follow-up (26 weeks)., Findings: Normal (versus reduced) CYP2B6 activity was associated with increased cessation at week 7, which was mediated by higher hydroxybupropion concentration [odds ratio (OR) = 1.25, 95% confidence interval (CI) = 1.03, 1.78]; this mediation effect persisted at week 26 (OR = 1.23, 95% CI = 1.02, 1.70). The mediation effect was similar in women (n = 116; OR = 1.33, 95% CI = 1.01, 2.30) and men (n = 57; OR = 1.33, 95% CI = 0.92, 3.87). Moreover, sex did not appear to moderate the mediation effect, although this should be tested in a larger sample., Conclusions: In African American light smokers with verified early bupropion use, genetically normal CYP2B6 activity appears to be indirectly associated with greater smoking cessation success in a relationship mediated by higher hydroxybupropion concentration. The mediating effect of higher hydroxybupropion concentration on smoking cessation persists beyond the active treatment phase and does not appear to differ by sex., (© 2021 Society for the Study of Addiction.)

Introduction: Bupropion is metabolized to its active metabolite, hydroxybupropion (HB), by the genetically polymorphic cytochrome P450 2B6 (CYP2B6) enzyme. Despite its significant role in bupropion metabolism, the magnitude of the impact of CYP2B6 genotype on the exposure of bupropion has not been quantified., Objectives: A systematic review and meta-analysis was conducted to quantify the association of bupropion and HB exposure with CYP2B6 variant alleles and genotype-defined metabolizer phenotypes., Methods: MEDLINE, EMBASE, Web of Science, Scifinder, PsycINFO, and CENTRAL were screened to identify studies that met the following inclusion criteria (search updated on February 2021): (1) area under the plasma drug concentration-time curve (AUC) of bupropion and/or HB in relation to CYP2B6 genotypes was studied, and (2) study participants were genotyped for common CYP2B6 variant alleles including at least CYP2B6*6. The Newcastle Ottawa Scale was used to assess risk of bias in each included study. The ratio of means (RoM) between CYP2B6 genotype or genotype-defined phenotype groups for bupropion exposure was calculated for each study and combined in a meta-analysis., Results: Eleven studies met the inclusion criteria for this systematic review, and 10 (including N = 413 participants) were included in the meta-analysis. All 10 studies involved healthy adult volunteers, where other medications were not allowed. The AUCs of HB and the active moiety (bupropion + HB) were significantly reduced in CYP2B6*6 carriers compared with the non-carriers (HB: RoM 0.77, 95% CI 0.71-0.83; active moiety: RoM 0.81, 95% CI 0.75-0.88). Both CYP2B6 poor and intermediate metabolizers had significantly decreased exposures to HB and the active moiety than normal metabolizers., Conclusion: The CYP2B6*6 allele and genotype-determined CYP2B6 poor and intermediate metabolizer phenotypes are associated with significantly lower exposures to HB and the total active moiety. The findings of this study suggest opportunities to further study precision dosing strategies for bupropion therapy based on CYP2B6 genotype., (© 2021 Pharmacotherapy Publications, Inc.)

This phase 1 study characterized the effect of multiple doses of upadacitinib, an oral Janus kinase 1 selective inhibitor, on the pharmacokinetics of the cytochrome P450 (CYP) 2B6 substrate bupropion. Healthy subjects (n = 22) received a single oral dose of bupropion 150 mg alone (study period 1) and on day 12 of a 16-day regimen of upadacitinib 30 mg once daily (study period 2). Serial blood samples for measurement of bupropion and hydroxybupropion plasma concentrations were collected in each study period. The central values (90% confidence intervals) for the ratios of change were 0.87 (0.79-0.96) for bupropion maximum plasma concentration (C max ), 0.92 (0.87-0.98) for bupropion area under the plasma-concentration time curve from time 0 to infinity (AUC inf ), 0.78 (0.72-0.85) for hydroxybupropion C max , and 0.72 (0.67-0.78) for hydroxybupropion AUC inf when administered with, relative to when administered without, upadacitinib. After multiple-dose administration of upadacitinib 30 mg once daily, upadacitinib mean ± SD AUC 0-24 was 641 ± 177 ng·h/mL, and C max was 83.3 ± 30.7 ng/mL. These results confirm that upadacitinib has no relevant effect on pharmacokinetics of substrates metabolized by CYP2B6., (© 2020 AbbVie Inc. Clinical Pharmacology in Drug Development published by Wiley Periodicals LLC on behalf of American College of Clinical Pharmacology.)

Bupropion is hydroxylated to its primary active metabolite hydroxybupropion by cytochrome P450 enzyme CYP2B6. In vitro data suggest the existence of alternative hydroxylation pathways mediated by the highly polymorphic enzyme CYP2C19. However, the impact of its genetic variants on bupropion metabolism in vivo is still under investigation. We report the case of a 28-year-old male Caucasian outpatient suffering from major depressive disorder who did not respond to a treatment with bupropion. Therapeutic drug monitoring revealed very low serum concentrations of both bupropion and hydroxybupropion. Genotyping identified a heterozygous status for the gain-of-function allele with the genotype CYP2C19*1/*17 predicting enhanced enzymatic activity. The present case shows a reduced bupropion efficacy, which may be explained by a reduced active moiety of bupropion and its active metabolite hydroxybupropion, due to alternative hydroxylation pathways mediated by CYP2C19 in an individual with CYP2C19 rapid metabolizer status. The case report thus illustrates the clinical relevance of therapeutic drug monitoring in combination with pharmacogenetics diagnostics for a personalized treatment approach.

Therapeutic drug monitoring (TDM) has become a clinical routine in psychiatry. Nevertheless, for bupropion there is only one method available that is suitable for routine use. However, it involves a complex sample clean-up. Owing to the instability of bupropion in serum, the main and active metabolite hydroxybupropion was chosen as the target substance. Therefore, a simple and robust high-performance liquid chromatography method for the quantification of hydroxybupropion in serum was developed and validated. A volume of 30 μL serum was used for easy sample clean-up, based on protein precipitation with acetonitrile followed by online solid-phase extraction. As hydroxybupropion was present in high serum concentrations, UV detection was possible. Owing to the commonly available instrumentation, the method could easily be integrated in routine TDM. The newly developed method was validated following the guidelines for bioanalytical method validation of the European Medicines Agency and US Food and Drug Administration. The lower limit of quantification was 100 ng/mL (0.391 μm) and linearity was shown between 100 and 2500 ng/mL. Intraday and interday precision ranged from 1.17 to 6.79% and from 6.07 to 9.41%, respectively. Intraday and interday accuracy ranged from 89.97 to 110.86% and from 95.05 to 101.2%. The method was shown to be selective, accurate and precise. Additionally, the method was successfully implemented in the therapeutic drug monitoring laboratory of the Department of Psychiatry, Psychosomatics and Psychotherapy at the University Hospital of Würzburg, Germany. Six months of routine analysis showed a rather low correlation between applied dose and serum concentration and therefore the necessity of TDM for dose-individualization in the treatment with bupropion., (© 2019 John Wiley & Sons, Ltd.)

1. Bupropion, an antidepressant drug has been approved as a racemate containing equal amounts of R- and S-enantiomers. Recently, the chirality of bupropion has received significant attention in the delineation of stereoselective pharmacokinetic (PK) and disposition data. Although the non-stereoselective metabolism of bupropion was well established, the emerging data suggest that bupropion exhibits complex stereoselective metabolism, leading to the formation of various stereoisomeric metabolites. Along with the chiral PKs of bupropion, hydroxybupropion, threohydrobupropion and erythrohydrobupropion, the metabolism data also provided insights into the roles of both CYP2B6 and CYP2C19 enzymes in the stereoselective disposition. Furthermore, the metabolism studies also suggested specific involvement of CYP2B6 pathway in the stereoselective hydroxylation of bupropion to R,R-hydroxybupropion, which was considered as a better marker for CYP2B6 activity. 2. Other significant learnings were: (1) understanding the in vivo CYP2D6 inhibitory potential of bupropion with respect to the chirality of parent drug and the metabolites; (2) the potential involvement of bupropion and metabolites towards significant down regulation of CYP2D6 mRNA; (3) significant in vivo CYP2D6 inhibitory activity (86%) exhibited by R,R-hydroxybupropion and threohydrobupropion. 3. The newly published data on chiral PKs and disposition of bupropion and its metabolites can be used to gauge the drug-drug interaction potential when bupropion is combined in clinical therapy. Moreover, such data would be useful to understand the consequences (if any), due to the combination of bupropion with other drugs both from a safety and efficacy perspective because of the prevalence of polypharmacy situations in many therapeutic areas including CNS indications.

BACKGROUND Bupropion (BUP) is an antidepressant and its pharmacological activity is mediated by its major metabolite, hydroxybupropion (HBUP). We investigated the effects of genetic polymorphisms of CYP2B6 on BUP and HBUP to provide certain evidence on the clinical rational administration of BUP. MATERIAL AND METHODS Plasma BUP and HBUP concentrations were assayed using high performance liquid chromatography-tandem mass spectrometry (HPLC-MS/MS). RESULTS A total of 23 healthy volunteers (eleven participants with CYP2B6*1/*1, 7 participants with CYP2B6*1/*6, 3 participants with CYP2B6*4/*6, and 2 participants with CYP2B6*1/*4) received orally administered 150 mg of BUP according to protocol. Blood samples were obtained up to 96 hours after administration. The whole blood was subject to genotyping by polymerase chain reaction and restriction fragment length polymorphism (PCR-RFLP). The concentration-time curve (AUC(0→96)), maximum plasma concentration (Cmax), and terminal half-life (t1/2) values of BUP in CYP2B6*1/*4 were lower than those of CYP2B6*1/*1. By contrast, the time to Cmax (tmax) value of the former was higher than that of the latter. The HBUP AUC(0→96) values in CYP2B6*4/*6 and CYP2B6*1/*4 increased to values 1.12-fold and 1.98-fold, compared with CYP2B6*1/*1 carriers. However, the HBUP AUC(0→96) value in CYP2B6*1/*1 was 1.51-fold higher than that in CYP2B6*1/*6. Similarly, the HBUP Cmax values in CYP2B6*4/*6 and CYP2B6*1/*4 increased by 1.12-fold and 1.97-fold, whereas the HBUP Cmax value in CYP2B6*1/*6 decreased to a value 1.64-fold lower than that in CYP2B6*1/*1. CONCLUSIONS Genetic polymorphisms of CYP2B6 influence the pharmacokinetic parameters of BUP and HBUP and thus establish rational BUP administration for Chinese patients in clinical settings.

A simple and efficient high-performance thin-layer chromatographic method was developed for chiral separation of rac-bupropion (BUP) and its active metabolite rac-hydroxybupropion (HBUP). Design of experiment (DoE)-based optimization was adopted instead of a conventional trial-and-error approach. The Box-Behnken design surface response model was used and the operating variables were optimized based on 17 trials design. The optimized method involved impregnation of chiral reagent, L(+)-tartaric acid, in the stationary phase with simultaneous addition in the mobile phase, which consisted of acetonitrile : methanol : dichloromethane : 0.50% L-tartaric acid (6.75:1.0:1.0:0.25, v/v/v/v). Under the optimized conditions, the resolution factor between the enantiomers of BUP and HBUP was 6.30 and 9.26, respectively. The limit of detection and limit of quantitation for (R)-BUP, (S)-BUP, (R,R)-HBUP, and (S,S)-HBUP were 9.23 and 30.78 ng spot -1 , 10.32 and 34.40 ng spot -1 , 12.19 and 40.65 ng spot -1 , and 14.26 and 47.53 ng spot -1 , respectively. The interaction of L-tartaric acid with analytes and their retention behavior was thermodynamically investigated using van't Hoff's plots. The developed method was validated as per the International Conference on Harmonization guidelines. Finally, the method was successfully applied to resolve and quantify the enantiomeric content from marketed tablets as well as spiked plasma samples., (© 2016 Wiley Periodicals, Inc.)

The FDA-approved antidepressant and smoking cessation drug bupropion is known to inhibit dopamine and norepinephrine reuptake transporters, as well as nicotinic acetylcholine receptors (nAChRs) which are cation-conducting members of the Cys-loop superfamily of ion channels, and more broadly pentameric ligand-gated ion channels (pLGICs). In the present study, we examined the ability of bupropion and its primary metabolite hydroxybupropion to block the function of cation-selective serotonin type 3A receptors (5-HT 3A Rs), and further characterized bupropion's pharmacological effects at these receptors. Mouse 5-HT 3A Rs were heterologously expressed in HEK-293 cells or Xenopus laevis oocytes for equilibrium binding studies. In addition, the latter expression system was utilized for functional studies by employing two-electrode voltage-clamp recordings. Both bupropion and hydroxybupropion inhibited serotonin-gated currents from 5-HT 3A Rs reversibly and dose-dependently with inhibitory potencies of 87 μM and 112 μM, respectively. Notably, the measured IC 50 value for hydroxybupropion is within its therapeutically-relevant concentrations. The blockade by bupropion was largely non-competitive and non-use-dependent. Unlike its modulation at cation-selective pLGICs, bupropion displayed no significant inhibition of the function of anion-selective pLGICs. In summary, our results demonstrate allosteric blockade by bupropion of the 5-HT 3A R. Importantly, given the possibility that bupropion's major active metabolite may achieve clinically relevant concentrations in the brain, our novel findings delineate a not yet identified pharmacological principle underlying its antidepressant effect., (Copyright © 2016 Elsevier Ltd. All rights reserved.)

Bupropion and its three active metabolites exhibit clinical efficacy in the treatment of major depression, seasonal depression and smoking cessation. The pharmacokinetics of bupropion in humans is highly variable. It is not known if there are any non-reported metabolites formed in humans in addition to the three known active metabolites. This paper reports newly identified and non-reported metabolites of bupropion in human plasma samples. Human subjects were dosed with a single oral dose of 75 mg of an immediate release bupropion HCl tablet. Plasma samples were collected and analysed by LC-MS/MS at 0, 6 and 24 h. Two non-reported metabolites (M1 and M3) were identified with mass-to-charge (m/z) ratios of 276 (M1, hydration of bupropion) and 258 (M3, hydroxylation of threo/erythrohydrobupropion) from human plasma in addition to the known hydroxybupropion, threo/erythrohydrobupropion and the glucuronidation products of the major metabolites (M2 and M4-M7). These new metabolites may provide new insight and broaden the understanding of bupropion's variability in clinical pharmacokinetics. © 2016 The Authors Biopharmaceutics & Drug Disposition Published by John Wiley & Sons Ltd., (© 2016 The Authors Biopharmaceutics & Drug Disposition Published by John Wiley & Sons Ltd.)

The interaction of (±)-bupropion [(±)-BP] with the human (h) α4β2 nicotinic acetylcholine receptor (AChR) was compared to that for its photoreactive analog (±)-2-(N-tert-butylamino)-3'-iodo-4'-azidopropiophenone [(±)-SADU-3-72]. Ca 2+ influx results indicated that (±)-SADU-3-72 and (±)-BP inhibit hα4β2 AChRs with practically the same potency. However, (±)-SADU-3-72 binds to the [ 3 H]imipramine sites at resting and desensitized hα4β2 AChRs with 3-fold higher affinity compared to that for (±)-BP, which is supported by molecular docking results. The docking results also indicate that each isomer of BP and SADU-3-72, in the protonated state, interacts with luminal and non-luminal sites. In the channel lumen, both ligands bind to two overlapping subsites, one that overlaps the imipramine site, and another much closer to the cytoplasmic side. The results suggest, for the first time, three differentiated non-luminal domains, including the transmembrane (TMD), extracellular (ECD), and ECD-TMD junction. In the ECD-TMD junction, BP and SADU-3-72 bind to overlapping sites. Interestingly, only SADU-3-72 binds to intrasubunit and intersubunit sites in the TMD, and to additional sites in the ECD. Our results are consistent with a model where BP and SADU-3-72 bind to overlapping sites in the luminal and ECD-TMD junctional domains of the hα4β2, whereas only SADU-3-72 binds to additional non-luminal sites. The BP junctional site opens the door for additional inhibitory mechanisms. The pharmacological properties of (±)-SADU-3-72 showed in this work support further photolabeling studies to mapping the BP binding sites in the hα4β2 AChR., (Copyright © 2016 Elsevier Ltd. All rights reserved.)

Bupropion sustained release is used to promote smoking cessation in males and nonpregnant females. However, its efficacy as a smoking cessation aid during pregnancy is not reported. The pregnancy-associated changes in maternal physiology may alter the pharmacokinetics and pharmacodynamics of bupropion and consequently its efficacy in pregnant smokers. Therefore, the aims of this study were to determine the steady-state pharmacokinetics of bupropion during pregnancy and the effect of functional genetic variants of CYP2B6 and CYP2C19 on bupropion pharmacokinetics in pregnant women. Plasma and urine concentrations of bupropion and its metabolites hydroxybupropion (OHBUP), threohydrobupropion, and erythrohydrobupropion were determined by liquid chromatography-mass spectrometry. Subjects were genotyped for five nonsynonymous single-nucleotide polymorphisms that result in seven CYP2B6 alleles, namely *2, *3, *4, *5, *6, *7, and *9, and for CYP2C19 variants *2, *3, and *17 The present study reports that the isoform-specific effect of pregnancy on bupropion-metabolizing enzymes along with the increase of renal elimination of the drug could collectively result in a slight decrease in exposure to bupropion in pregnancy. In contrast, pregnancy-induced increase in CYP2B6-catalyzed bupropion hydroxylation did not impact the plasma levels of OHBUP, probably due to a higher rate of OHBUP glucuronidation, and renal elimination associated with pregnancy. Therefore, exposure to OHBUP, a pharmacologically active metabolite of the bupropion, appears to be similar to that of the nonpregnant state. The predicted metabolic phenotypes of CYP2B6*6 and variant alleles of CYP2C19 in pregnancy are similar to those in the nonpregnant state., (Copyright © 2016 by The American Society for Pharmacology and Experimental Therapeutics.)

Bupropion is a widely used antidepressant, smoking cessation aid, and weight-loss therapy. It is administered as a racemic mixture, but the pharmacokinetics and activity of bupropion are stereoselective. The activity and side effects of bupropion are attributed to bupropion and its metabolites S,S- and R,R-OH-bupropion, threohydrobupropion, and erythrohydrobupropion. Yet the stereoselective metabolism in vitro and the enzymes contributing to the stereoselective disposition of bupropion have not been characterized. In humans, the fraction of bupropion metabolized (fm) to the CYP2B6 probe metabolite OH-bupropion is 5-16%, but ticlopidine increases bupropion exposure by 61%, suggesting a 40% CYP2B6 and/or CYP2C19 fm for bupropion. Yet, the CYP2C19 contribution to bupropion clearance has not been defined, and the enzymes contributing to overall bupropion metabolite formation have not been fully characterized. The aim of this study was to characterize the stereoselective metabolism of bupropion in vitro to explain the stereoselective pharmacokinetics and the effect of drug-drug interactions (DDIs) and CYP2C19 pharmacogenetics on bupropion exposure. The data predict that threohydrobupropion accounts for 50 and 82%, OH-bupropion for 34 and 12%, erythrohydrobupropion for 8 and 4%, and 4'-OH-bupropion for 8 and 2% of overall R- and S-bupropion clearance, respectively. The fm,CYP2B6 was predicted to be 21%, and the fm,CYP2C19, 6% for racemic bupropion. Importantly, ticlopidine was found to inhibit all metabolic pathways of bupropion in vitro, including threohydrobupropion, erythrohydrobupropion, and 4'OH-bupropion formation, explaining the in vivo DDI. The stereoselective pharmacokinetics of bupropion were quantitatively explained by the in vitro metabolic clearances and in vivo interconversion between bupropion stereoisomers., (Copyright © 2016 by The Author(s).)

Background: Bupropion is used for treatment of depression during pregnancy. However, its use as a smoking cessation aid for pregnant women is currently under evaluation., Objective: The aim of this opportunistic study was to investigate the transfer of bupropion and its major pharmacologically active metabolites, hydroxybupropion and threohydrobupropion, across the placenta in vivo. In addition, the concentrations of the drug and its metabolites were determined in the amniotic fluid., Study Design: The following samples were collected at deliveries from 22 women taking bupropion: maternal blood (n = 22), umbilical cord venous blood (n = 22), and amniotic fluid (n = 9). The concentrations of the drug and its metabolites in blood plasma and amniotic fluid were determined by means of liquid chromatography-mass spectrometry. Placental passage was calculated as a ratio of umbilical cord venous plasma to maternal plasma concentrations., Results: The levels of hydroxybupropion and threohydrobupropion in umbilical cord venous plasma were invariably lower than their corresponding concentrations in maternal plasma. The concentrations of bupropion in umbilical cord plasma were lower than in maternal plasma in the majority of the maternal-cord blood pairs. The median values of the umbilical cord venous plasma to maternal plasma ratios were: bupropion, 0.53 (interquartile range 0.35, n = 18), hydroxybupropion, 0.21 (interquartile range 0.12, n = 18), and threohydrobupropion, 0.61 (interquartile range 0.11, n = 21). In umbilical cord venous plasma, the median concentration of bupropion was 5.3 ng/mL; hydroxybupropion, 103.6 ng/mL; and threohydrobupropion, 59.6 ng/mL. Bupropion and its metabolites were detectable in the amniotic fluid but the concentrations of threohydrobupropion were higher than those in the corresponding umbilical cord venous plasma., Conclusion: Bupropion and its active metabolites cross the placenta to the fetal circulation. The concentrations of hydroxybupropion and threohydrobupropion in umbilical cord venous plasma were higher than bupropion concentrations suggesting a higher fetal exposure to the metabolites than the parent drug. The higher levels of threohydrobupropion in the amniotic fluid than those in umbilical cord venous plasma suggest that enzymes involved in the metabolism of bupropion to threohydrobupropion are most likely active in the fetus. The biological consequences of fetal exposure to maternally administered bupropion and/or its active metabolites via placental transfer and recirculation of the amniotic fluid are yet to be determined., (Copyright © 2016. Published by Elsevier Inc.)

A stereoselective assay was developed for the quantification of bupropion and oxidative, reductive, and glucuronide metabolites (16 analytes total) in human urine. Initially, authentic glucuronide standards obtained from commercial sources were found to be incorrectly labeled with regard to stereochemistry; the correct stereochemistry was unequivocally reassigned. A trifurcated urine sample preparation and analysis procedure was employed for the stereoselective analysis of bupropion, hydroxybupropion, erythrohydrobupropion, and threohydrobupropion enantiomers, and hydroxybupropion, erythrohydrobupropion and threohydrobupropion β-d-glucuronide diastereomers in urine. Method 1 stereoselectively analyzed bupropion (R and S), and unconjugated free hydroxybupropion (R,R and S,S), erythrohydrobupropion (1R,2S and 1S,2R), and threohydrobupropion (1R,2R and 1S,2S) using chiral chromatography with an α1-acid glycoprotein column. Because no hydroxybupropion β-d-glucuronide standards were commercially available, method 2 stereoselectively analyzed total hydroxybupropion aglycones (R,R and S,S-hydroxybupropion) after urine hydrolysis by β-glucuronidase. Hydroxybupropion β-d-glucuronide (R,R and S,S) urine concentrations were calculated as the difference between total and free hydroxybupropion (R,R and S,S) concentrations. Due to incomplete β-glucuronidase hydrolysis of erythrohydrobupropion and threohydrobupropion β-d-glucuronide diastereomers, method 3 stereoselectively analyzed intact erythrohydrobupropion and threohydrobupropion β-d-glucuronide diastereomers using C18 column chromatography. All analytes were quantified by positive ion electrospray tandem mass spectrometry. The assay was fully validated over analyte-specific concentrations. Intra- and inter assay precision were within 15% for each analyte. The limits of quantification for bupropion (R and S), hydroxybupropion (R,R and S,S), threohydrobupropion (1S,2S and 1R,2R), erythrohydrobupropion (1R,2S and 1S,2R) were 10, 50, 100, and 100ng/mL, respectively. The limits of quantification for (1R,2R)-threohydrobupropion β-d-glucuronide, (1S,2S)-threohydrobupropion β-d-glucuronide, and (1R,2R)-erythrohydrobupropion β-d-glucuronide were each 50ng/mL. Due to the abundance of bupropion and metabolites in human urine, no efforts were made to optimize sensitivity. All analytes were stable following freeze thaw cycles at -80°C. This assay was applicable to clinical pharmacokinetic investigations of bupropion in patients and to in vitro metabolism of the primary bupropion metabolites to their glucuronides., (Copyright © 2016 Elsevier B.V. All rights reserved.)

Although CYP2B6 catalyzes the biotransformation of many drugs used clinically for children and adults, information regarding the effects of development on CYP2B6 expression and activity are scarce. Utilizing a large panel of human liver samples (201 donors: 24 fetal, 141 pediatric, and 36 adult), we quantified CYP2B6 mRNA and protein expression levels, characterized CYP2B6 (bupropion hydroxylase) activity in human liver microsomes (HLMs), and performed an extensive genotype analysis to differentiate CYP2B6 haplotypes such that the impact of genetic variation on these parameters could be assessed. Fetal livers contained extremely low levels of CYP2B6 mRNA relative to postnatal samples and fetal HLMs did not appear to catalyze bupropion hydroxylation; however, fetal CYP2B6 protein levels were not significantly different from postnatal levels. Considerable interindividual variation in CYP2B6 mRNA expression, protein levels, and activity was observed in postnatal HLMs (mRNA, ∼40,000-fold; protein, ∼300-fold; activity, ∼600-fold). The extremely wide range of interindividual variability in CYP2B6 expression and activity was significantly associated with age (P < 0.01) following log transformation of the data. Our data suggest that CYP2B6 activity appears as early as the first day of life, increases through infancy, and by 1 year of age, CYP2B6 levels and activity may approach those of adults. Surprisingly, CYP2B6 interindividual variability was not significantly associated with genetic variation in CYP2B6, nor was it associated with differences in gender or ethnicity, suggesting that factors other than these are largely responsible for the wide range of variability in CYP2B6 expression and activity observed among a large group of individuals/samples., (Copyright © 2016 by The American Society for Pharmacology and Experimental Therapeutics.)

Administration of bupropion [(±)-2-(tert-butylamino)-1-(3-chlorophenyl)propan-1-one] and its preformed active metabolite, hydroxybupropion [(±)-1-(3-chlorophenyl)-2-[(1-hydroxy-2-methyl-2-propanyl)amino]-1-propanone], to rats with measurement of unbound concentrations by quantitative microdialysis sampling of plasma and brain extracellular fluid was used to develop a compartmental pharmacokinetics model to describe the blood-brain barrier transport of both substances. The population model revealed rapid equilibration of both entities across the blood-brain barrier, with resultant steady-state brain extracellular fluid/plasma unbound concentration ratio estimates of 1.9 and 1.7 for bupropion and hydroxybupropion, respectively, which is thus indicative of a net uptake asymmetry. An overshoot of the brain extracellular fluid/plasma unbound concentration ratio at early time points was observed with bupropion; this was modeled as a time-dependent uptake clearance of the drug across the blood-brain barrier. Translation of the model was used to predict bupropion and hydroxybupropion exposure in human brain extracellular fluid after twice-daily administration of 150 mg bupropion. Predicted concentrations indicate that preferential inhibition of the dopamine and norepinephrine transporters by the metabolite, with little to no contribution by bupropion, would be expected at this therapeutic dose. Therefore, these results extend nuclear imaging studies on dopamine transporter occupancy and suggest that inhibition of both transporters contributes significantly to bupropion's therapeutic efficacy., (Copyright © 2016 by The American Society for Pharmacology and Experimental Therapeutics.)

A stereoselective analytical method was developed and validated for the quantification of bupropion, and principle metabolites hydroxybupropion, erythrohydrobupropion and threohydrobupropion in human plasma. Separation of individual enantiomers (R)-bupropion, (S)-bupropion, (R,R)-hydroxybupropion, (S,S-hydroxybupropion), (1S,2S)-threohydrobupropion, (1R,2R)-threohydrobupropion, (1R,2S)-erythrohydrobupropion, and (1S,2R)-erythrohydrobupropion was achieved utilizing an α1-acid glycoprotein column within a 12-min run time. Chromatograph separation was significantly influenced by mobile phase pH and variability between columns. Analytes were quantified by positive ion electrospray tandem mass spectrometry following plasma protein precipitation with 20% trichloroacetic acid. Identification of erythrohydrobupropion enantiomer peaks and threohydrobupropion enantiomer peaks was achieved by sodium borohydride reduction of enantiopure (R)- and (S)-bupropion. Initial assay validation and sensitivity determination was on AB Sciex 3200, 4000 QTRAP, and 6500 mass spectrometers. Accuracy and precision were within 15% for each analyte. The assay was fully validated over analyte-specific concentrations using an AB Sciex 3200 mass spectrometer. Intra- and inter-assay precision and accuracy were within 12% for each analyte. The limits of quantification for bupropion (R and S), hydroxybupropion (R,R and S,S), threohydrobupropion (1S,2S and 1R,2R), and erythrohydrobupropion (1R,2S and 1S,2R) were 0.5, 2, 1, and 1ng/mL, respectively. All analytes were stable following freeze thaw cycles at -80°C and while stored at 4°C in the instrument autosampler. This method was applicable to clinical pharmacokinetic investigations of bupropion in patients. This is the first chromatographic method to resolve erythrohydrobupropion and threohydrobupropion enantiomers, and the first stereoselective LC-MS/MS assay to quantify bupropion, and principle metabolites hydroxybupropion, erythrohydrobupropion, and threohydrobupropion in human plasma., (Copyright © 2016 Elsevier B.V. All rights reserved.)

Bupropion metabolites formed via oxidation and reduction exhibit pharmacological activity, but little is known regarding their stereoselective disposition. A novel stereoselective liquid chromatography-tandem mass spectrometry (LC-MS/MS) method was developed to separate and quantify enantiomers of bupropion, 4-hydroxybupropion, and erythro- and threo-dihydrobupropion. Liquid-liquid extraction was implemented to extract all analytes from 50 μL human plasma. Acetaminophen (APAP) was used as an internal standard. The analytes were separated on a Lux 3 μ Cellulose-3 250×4.6 mm column by methanol: acetonitrile: ammonium bicarbonate: ammonium hydroxide gradient elution and monitored using an ABSciex 5500 QTRAP triple-quadrupole mass spectrometer equipped with electrospray ionization probe in positive mode. Extraction efficiency for all analytes was ≥70%. The stability at a single non-extracted concentration for over 48 h at ambient temperature resulted in less than 9.8% variability for all analytes. The limit of quantification (LOQ) for enantiomers of bupropion and 4-hydroxybupropion was 0.3 ng/mL, while the LOQ for enantiomers of erythro- and threo-hydrobupropion was 0.15 ng/mL. The intra-day precision and accuracy estimates for enantiomers of bupropion and its metabolites ranged from 3.4% to 15.4% and from 80.6% to 97.8%, respectively, while the inter-day precision and accuracy ranged from 6.1% to 19.9% and from 88.5% to 99.9%, respectively. The current method was successfully implemented to determine the stereoselective pharmacokinetics of bupropion and its metabolites in 3 healthy volunteers administered a single 100mg oral dose of racemic bupropion. This novel, accurate, and precise HPLC-MS/MS method should enhance further research into bupropion stereoselective metabolism and drug interactions., (Copyright © 2016 Elsevier B.V. All rights reserved.)

Background: The clinical effect of bupropion is mediated by its active metabolite hydroxybupropion. Previous studies have reported conflicting impact of the CYP2B6*6 variant allele on the formation of hydroxybupropion from bupropion. The aim of this study was to clarify the effect of CYP2B6*6 and secondarily CYP2D6 genotype on steady-state serum concentrations of bupropion and hydroxybupropion in a large population of psychiatric patients., Methods: Retrospective information about dose-adjusted serum concentrations (C/D ratios) of bupropion and hydroxybupropion, CYP2B6 genotype (ie, data on the 2B6*6 polymorphisms 516G>T and 785A>G) and CYP2D6 genotype, was obtained from a therapeutic drug monitoring database (n = 132 patients). C/D ratios of bupropion and hydroxybupropion, and metabolic ratios, were compared between CYP2B6 genotype subgroups by multivariate mixed-model analyses (2B6*1/*1 was defined as control group). In the analyses, CYP2D6 genotype was also included as a covariate., Results: Homozygous 2B6*6 carriers (n = 7) had significantly lower C/D ratios of hydroxybupropion compared with controls (n = 79), that is, estimated mean 5.8 versus 13.0 nmol·L·mg (P < 0.001). C/D ratio of hydroxybupropion in heterozygous *6 carriers (12.1 nmol·L·mg; n = 46) did not significantly differ compared with controls (P = 0.32). The hydroxybupropion/bupropion metabolic ratios in heterozygous and homozygous 2B6*6 carriers were significantly lower than in controls (P = 0.001 and P < 0.001, respectively). CYP2D6 genotype did not significantly alter the hydroxybupropion C/D ratio, but higher bupropion values were observed in poor versus extensive CYP2D6 metabolizers (P = 0.020)., Conclusions: This study shows that the CYP2B6*6 variant allele is associated with significantly reduced formation of the active bupropion metabolite in psychiatric patients. Our findings suggest that dose-adjusted serum concentrations of hydroxybupropion at steady state is approximately halved in homozygous CYP2B6*6 carriers, which might imply risk of reduced clinical response in this patient subgroup. The CYP2D6 genotype does not affect hydroxybupropion concentrations and is therefore unlikely to impact bupropion treatment.

Data from 2 pediatric single-dose studies, conducted at the same center, were combined to evaluate exposure levels of bupropion and metabolites in adolescents 12-17 years old, compared with adults > 18 years. Pharmacokinetic analyses of bupropion and its metabolites were performed using normalization and pharmacological/convulsive weighting methods on exposure. When compared with adults (>18 years), subjects 12-14 years had an increase in weight-normalized exposure to bupropion (ie, Cmax , 78%; AUC0-t , 83%; and AUCinf , 85%). Variability in this younger age group was also higher, with observations of a 3- to 4-fold increase in exposure. When the changes in metabolites were accounted within pharmacological and convulsive-weighted exposures, the relative ratio of 12-14 years to adults in body weight-normalized Cmax was 127% and 110%, respectively. Subjects 15-17 years did not exhibit a difference in exposure compared with adults. The influence of age on bupropion pharmacokinetics demonstrates that, in general, healthy adolescent subjects cannot be considered smaller healthy adult subjects; the increase in exposure is inversely related to age and appears to be solely associated with bupropion, not with its metabolites. Because there are no clinical safety and efficacy data of bupropion in adolescents, this data may shift its risk-benefit profile., (© 2015, The American College of Clinical Pharmacology.)

Background: Preclinical studies with bupropion in rodent models of nicotine dependence have generated equivocal findings with regard to translating the clinical efficacy of the antidepressant as a smoking cessation agent., Objective: Given that rats are poor metabolizers of bupropion, the present experiments examined (2S,3S)-hydroxybupropion, the major active metabolite, on the positive reinforcing and aversive stimulus properties of nicotine in rats., Methods: In male hooded Lister rats, (2S,3S)-hydroxybupropion (1.0-10.0 mg/kg IP) was tested on intravenous nicotine (0.03 mg/kg/inf) self-administration behaviour for three sessions (n = 8), and in another experiment, the same doses of (2S,3S)-hydroxybupropion were tested in a conditioned taste aversion procedure to assess the aversive stimulus properties of nicotine, a function implicated in the regulation of nicotine intake., Results: (2S,3S)-hydroxybupropion attenuated nicotine intake in a manner similar to that produced by mecamylamine pretreatment (1.0 mg/kg SC). This effect on nicotine-taking was specific since these doses had no effect on responding maintained by sucrose presented orally (200 μl of 5 % w/v). (2S,3S)-hydroxybupropion (1, 3 and 10 mg/kg IP) pretreatment failed to modify the aversive effects produced by a small dose of nicotine (0.1 mg/kg SC)., Conclusions: These results demonstrate this metabolite to specifically modify the positive reinforcing effects of nicotine without affecting its aversive motivational effects. We propose that the clinical efficacy of bupropion may be due to a combination of effects produced by bupropion and/or its active metabolite (2S,3S)-hydroxybupropion involving the inhibition of reuptake of dopamine and noradrenaline in reward centres of the brain and the noncompetitive antagonism of neuronal nicotinic receptors.

This paper describes the synthesis of deuterium-labeled hydroxybupropion. Mass spectrometry analysis of the compound revealed over 98% deuterium enrichment., (Copyright © 2015 John Wiley & Sons, Ltd.)

Objectives: Depression is a rapidly growing issue in the United States. There are many drug classes that may be used to treat depression, including the selective serotonin-reuptake inhibitors (SSRIs) citalopram (Celexa®) and sertraline (Zoloft®), as well as the aminoketone bupropion (Wellbutrin®). However, therapeutic efficacy and treatment success is often variable, requiring changes in dosing regimens or drug selection. Methods for drug quantification can become important tools in the assessment of drug efficacy to optimize treatment regimens. Here, we present a turbulent flow-liquid chromatography-tandem mass spectrometric (TFC-MS/MS) method for the robust, simultaneous quantification of citalopram, sertraline, bupropion and its active metabolite, hydroxybupropion (OH-bupropion)., Design and Methods: Serum spiked with the aforementioned antidepressants, along with their corresponding isotopically labeled internal standards was subjected to protein precipitation. Samples were injected onto a TFC column for on-line solid phase extraction and a Hypersil Gold C18 column for chromatographic separation. Detection was achieved using a TSQ Vantage mass spectrometer. Assay validation followed FDA bioanalytical guidelines., Results: The analytical measuring range for all analytes spanned from 5 to 1000ng/mL. Intra- and inter-assay precision across four quality control levels were ≤9.2% and ≤14.8%, respectively. A comparison to other LC-MS/MS methods resulted in a strong correlation with correlation coefficients ranging from 0.9929 to 0.9971. Carryover, stability, recovery, matrix effects, extraction and processing efficiency were also deemed acceptable in accordance with FDA recommendations., Conclusions: The development and validation of this TFC-MS/MS method allow for the robust and high-throughput quantification of commonly prescribed antidepressants., (Copyright © 2014 The Canadian Society of Clinical Chemists. Published by Elsevier Inc. All rights reserved.)

Background: Bupropion is a dopamine and norepinephrine reuptake inhibitor approved for the treatment of depression and smoking cessation. According to the recently published reviews, it is a candidate for therapeutic drug monitoring (TDM) to improve therapeutic outcomes and reduce risks of intolerability or intoxication. In practice, however, the use of TDM is limited due to the chemical instability of bupropion. This investigation sought to determine if the major, active, and chemically stable metabolite 4-hydroxybupropion is a suitable measure to guide antidepressant drug therapy with bupropion., Methods: 4-Hydroxybupropion serum levels were measured using a newly developed and validated high-performance liquid chromatography assay with ultraviolet detection. They correlated with therapeutic effects measured by the clinical global impression scale for improvement., Results: The study included 52 patients (50% women). Patients who were markedly improved according to the clinical global impression scale score had significantly (P = 0.042) higher 4-hydroxybupropion serum levels than those with moderate or minimal improvement (mean ± SD, 1113 ± 576, 825 ± 398, and 475 ± 331 ng/mL, respectively). Analysis of receiver operating characteristics revealed significant predictive properties of 4-hydroxybupropion serum levels (P = 0.002) for marked improvement with a lower threshold level of 858 ng/mL. Under similar mean doses (265 ± 107 versus 239 ± 100 mg, respectively), women attained significantly higher serum levels than men (1050 ± 524 versus 589 ± 352 ng/mL, respectively) and exhibited a better therapeutic effect (P = 0.018)., Conclusions: Despite multiple limitations of this naturalistic study, evidence could be given that the measurement of 4-hydroxybupropion in serum is suitable to perform TDM for bupropion. Blood levels should be above 860 ng/mL to attain therapeutic improvement. Potential sex differences in bupropion pharmacokinetics, probably due to differential activities of CYP2B6, should be taken into account when the drug is prescribed.

An unusual, but clinically significant, digoxin (DIG)-bupropion (BUP) drug interaction (DDI), in which BUP increased DIG renal clearance by 80% is reported. To investigate the mechanism(s) of this unusual DDI, first the effect of BUP, its circulating metabolites or their combination on [(3) H]-DIG transport by cells expressing human P-gp or human OATP4C1 was determined. Second, the study asked whether this DDI could be replicated in the rat so that it could be used to conduct mechanistic studies. Then, the effect of BUP and its rat metabolites on [(3) H]-DIG transport were tested by cells expressing rat Oatp4c1. Bupropion and its metabolites had no effect on human P-gp mediated transepithelial transport of [(3) H]-DIG. Bupropion and hydroxybupropion (HBUP) significantly stimulated H-OATP4C1 mediated transport of [(3) H]-DIG. In addition, BUP cocktail (BUP plus its metabolites) significantly increased the H-OATP4C1 mediated transport of [(3) H]-DIG, and partially reversed the inhibition by 100 µm DIG. However, erythro-hydrobupropion (EBUP) and threo-hydrobupropion (TBUP) did not affect the [(3) H]-DIG uptake by H-OATP4C1 cells. Bupropion administration significantly increased digoxin renal clearance in rats. Surprisingly, bupropion significantly inhibited r-Oatp4c1 mediated transport of [(3) H]-DIG at clinically relevant unbound plasma concentrations of BUP or those observed in the rat study, while HBUP or TBUP did not. These data support our hypothesis that at clinically relevant plasma concentrations, bupropion and its metabolites activate H-OATP4C1 mediated DIG tubular secretion, and could possibly explain the increase in digoxin renal clearance produced by bupropion. While bupropion increased digoxin renal clearance in the rat, it appeared to do so by inhibiting r-Oatp4c1-mediated digoxin renal reabsorption., (Copyright © 2014 John Wiley & Sons, Ltd.)

Bupropion, introduced as an antidepressant in the 1980s, is also effective as a smoking cessation aid and is beneficial in the treatment of methamphetamine addiction, cocaine dependence, addictive behaviors such as pathological gambling, and attention deficit hyperactivity disorder. (2S,3S)-hydroxybupropion is an active metabolite of bupropion produced in humans that contributes to antidepressant and smoking cessation efficacy and perhaps benefits in other CNS disorders. Mechanisms underlying its antidepressant and smoking abstinence remain elusive. However, it seems likely that efficacy is due to a combination of the effects of bupropion and/or its active metabolite (2S,3S)-hydroxybupropion involving the inhibition of reuptake of dopamine (DA) and NE in reward centers of the brain and the noncompetitive antagonism of α4β2- and α3β4*-nAChRs. These combined effects of bupropion and its active metabolite may be responsible for its ability to decrease nicotine reward and withdrawal. Studies directed toward development of a bupropion analog for treatment of cocaine addiction led to compounds, typified by 2-(N-cyclopropylamino)-3'-chloropropiophenone (RTI-6037-39), thought to act as indirect DA agonists. In addition, (2S,3S)-hydroxybupropion analogs were developed, which had varying degrees of DA and NE uptake inhibition and antagonism of nAChRs. These compounds will be valuable tools for animal behavioral studies and as clinical candidates. Here, we review the (1) early studies leading to the development of bupropion, (2) bupropion metabolism and the identification of (2S,3R)-hydroxybupropion as an active metabolite, (3) mechanisms of bupropion and metabolite action, (4) effects in animal behavioral studies, (5) results of clinical studies, and (6) development of bupropion analogs as potential pharmacotherapies for treating nicotine and cocaine addiction., (© 2014 Elsevier Inc. All rights reserved.)

Bupropion is widely used as an antidepressant drug and also as a smoking cessation aid. In humans, this drug is extensively metabolized to form several metabolites. Oxidised hydroxybupropion and two reduced metabolites, threohydrobupropion and erythrohydrobupropion, are major metabolites. All of these metabolites are considered to be active. Although the oxidative metabolic pathway and the central role of CYP2B6 are known, the enzymes that participate in the reduction have not been identified to date. The aim of this study was to confirm the role of human liver subcellular fractions in the metabolism of bupropion and elucidate the contribution of particular carbonyl-reducing enzymes. An HPLC method for the determination of bupropion metabolites was utilised. Bupropion is reduced to threohydrobupropion and less to erythrohydrobupropion in human liver cytosol, microsomes and also mitochondria. Surprisingly, intrinsic clearance for formation of both metabolites is the highest in mitochondrial fraction. Moreover this study provides the first direct evidence that 11β-hydroxysteroid dehydrogenase 1, AKR1C1, AKR1C2, AKR1C3 and CBR1 participate in the reducing biotransformation of bupropion in vitro. The enzyme kinetics of all of these reductases was investigated and kinetic parameters were calculated.

Context: Bupropion overdose commonly causes generalized seizures and central nervous system depression. Less commonly, cardiotoxicity has been reported. The toxicity of the parent drug compared to its active metabolite hydroxybupropion is uncertain., Case Details: A 31-year-old man presented to the emergency department with altered mental status after an intentional overdose of bupropion. Three hours after admission he developed status epilepticus requiring intubation, and 13 h after admission he developed marked widening of the QRS complex and prolongation of the QTc interval. Serial serum bupropion levels peaked with the onset of cardiotoxicity (334 ng/mL) and fell into the therapeutic range within 24 h, which coincided with normalization of his ECG intervals. Levels of the metabolite hydroxybupropion peaked later (4302 ng/mL) and remained elevated even after neurological and cardiotoxic symptoms resolved., Discussion: Cardiotoxicity appears to be caused primarily by bupropion rather than its active metabolite hydroxybupropion.

Bupropion is widely used for treatment of depression and as a smoking-cessation drug. Despite more than 20 years of therapeutic use, its metabolism is not fully understood. While CYP2B6 is known to form hydroxybupropion, the enzyme(s) generating erythro- and threohydrobupropion have long remained unclear. Previous experiments using microsomal preparations and the nonspecific inhibitor glycyrrhetinic acid suggested a role for 11β-hydroxysteroid dehydrogenase 1 (11β-HSD1) in the formation of both erythro- and threohydrobupropion. 11β-HSD1 catalyzes the conversion of inactive glucocorticoids (cortisone, prednisone) to their active forms (cortisol, prednisolone). Moreover, it accepts several other substrates. Here, we used for the first time recombinant 11β-HSD1 to assess its role in the carbonyl reduction of bupropion. Furthermore, we applied human, rat, and mouse liver microsomes and a selective inhibitor to characterize species-specific differences and to estimate the relative contribution of 11β-HSD1 to bupropion metabolism. The results revealed 11β-HSD1 as the major enzyme responsible for threohydrobupropion formation. The reaction was stereoselective and no erythrohydrobupropion was formed. Human liver microsomes showed 10 and 80 times higher activity than rat and mouse liver microsomes, respectively. The formation of erythrohydrobupropion was not altered in experiments with microsomes from 11β-HSD1-deficient mice or upon incubation with 11β-HSD1 inhibitor, indicating the existence of another carbonyl reductase that generates erythrohydrobupropion. Molecular docking supported the experimental findings and suggested that 11β-HSD1 selectively converts R-bupropion to threohydrobupropion. Enzyme inhibition experiments suggested that exposure to bupropion is not likely to impair 11β-HSD1-dependent glucocorticoid activation but that pharmacological administration of cortisone or prednisone may inhibit 11β-HSD1-dependent bupropion metabolism.

Unlabelled: This study investigated the effects of pregnane X receptor (PXR/NR1I2) and CYP2B6 genetic variants on sodium ferulate (SF)-mediated induction of bupropion hydroxylation. The pharmacokinetics of bupropion and hydroxybupropion were evaluated after an oral dose of bupropion (150 mg) administered with and without SF pretreatment for 14 days in 33 healthy subjects. The area under the time-concentration curve (AUC) ratio of AUC&#95;hyd (AUC(0-∞) of hydroxybupropion)/AUC&#95;bup (AUC(0-∞) of bupropion) represents the CYP2B6 hydroxylation activity, which was significantly lower in CYP2B6*6 carriers (NR1I2 TGT noncarriers or carriers) than in noncarriers in both the basal and SF-induced states (p-value<0.05). AUC ratio and AUC&#95;hyd of NR1I2 -24113AA variant were markedly lower than GA and GG genotypes (7.5±2.1 versus 14.5±3.3 and 20.6±1.1, and 8873±1431 versus 14,504±2218 and 17,586±1046) in the induced states. However, -24020(-)/(-) variant didn't show significant difference in the induction of CYP2B6 hydroxylation activity by SF compared with other -24020[GAGAAG]/(-) genotypes. NR1I2 TGT haplotype (-25385T+g.7635G+g.8055T) carriers exhibited a significantly decreased AUC ratio, compared with TGT noncarriers, in the basal states (7.6±1.0 versus 9.7±1.0), while this result wasn't observed in CYP2B6*6 noncarriers. Moreover, individuals with complete mutation-type [CYP2B6*6/*6+NR1I2 TGT+ -24113AA+ -24020 (-)/(-)] showed even lower percent difference of AUC ratio (8.7±1.2 versus 39.5±8.2) than those with complete wild-type. In conclusion, it is suggested that NR1I2 variants decrease the bupropion hydroxylation induced by SF treatment, particularly in CYP2B6*6 carriers., Trial Registration: ChiCTR.org ChiCTR-TRC-11001285.

The pharmacological properties of (±)-2-(N-tert-butylamino)-3'-iodo-4'-azidopropiophenone [(±)-SADU-3-72], a photoreactive analog of bupropion (BP), were characterized at different muscle nicotinic acetylcholine receptors (AChRs) by functional and structural approaches. Ca²⁺ influx results indicate that (±)-SADU-3-72 is 17- and 6-fold more potent than BP in inhibiting human (h) embryonic (hα1β1γδ) and adult (hα1β1εδ) muscle AChRs, respectively. (±)-SADU-3-72 binds with high affinity to the [³H]TCP site within the resting or desensitized Torpedo AChR ion channel, whereas BP has higher affinity for desensitized AChRs. Molecular docking results indicate that both SADU-3-72 enantiomers interact with the valine (position 13') and serine (position 6') rings. However, an additional domain, between the outer (position 20') and valine rings, is observed in Torpedo AChR ion channels. Our results indicate that the azido group of (±)-SADU-3-72 may enhance its interaction with polar groups and the formation of hydrogen bonds at AChRs, thus supporting the observed higher potency and affinity of (±)-SADU-3-72 compared to BP. Collectively our results are consistent with a model where BP/SADU-3-72 and TCP bind to overlapping sites within the lumen of muscle AChR ion channels. Based on these results, we believe that (±)-SADU-3-72 is a promising photoprobe for mapping the BP binding site, especially within the resting AChR ion channel., (Copyright © 2012 Elsevier Ltd. All rights reserved.)

Bupropion is indicated to promote smoking cessation. Animal studies suggest that the pharmacologic activity of bupropion can be mediated by its major metabolite, hydroxybupropion. We measured plasma bupropion and its metabolite levels in a double-blind, placebo controlled, randomized smoking-cessation trial. Among the treatment-adherent individuals, higher hydroxybupropion concentrations (per μg/ml) resulted in better smoking-cessation outcomes (week 3, 7, and 26 odds ratio (OR) = 2.82, 2.96, and 2.37, respectively, P = 0.005-0.040); this was not observed with bupropion levels (OR = 1.00-1.03, P = 0.59-0.90). Genetic variation in CYP2B6, the enzyme that metabolizes bupropion to hydroxybupropion, was identified as a significant source of variability in hydroxybupropion formation. Our data indicate that hydroxybupropion contributes to the pharmacologic effects of bupropion for smoking cessation, and that variability in response to bupropion treatment is related to variability in CYP2B6-mediated hydroxybupropion formation. These findings suggest that dosing of bupropion to achieve a hydroxybupropion level of 0.7 μg/ml or increasing bupropion dose for CYP2B6 slow metabolizers could improve bupropion's cessation outcomes.

A liquid chromatography in tandem with electro-spray ionization mass spectrometry method has been developed and validated for the quantitative determination of bupropion and its major metabolites (hydroxybupropion, threo- and erythrohydrobupropion) in human umbilical cord plasma and placental tissue. The samples were acidified with trichloroacetic acid, and protein precipitated by adding acetonitrile. Chromatographic separation of drug and metabolites was achieved by using a Waters Symmetry C(18) column, with an isocratic elution of 31% methanol and 69% formic acid (0.04%, v/v) aqueous solution at a flow rate of 1.0 mL/min. Detection was carried out by mass spectrometry using positive electro-spray ionization mode, and the compounds were monitored using multiple reactions monitoring method. Deuterium-labeled isotopes of the compounds were used as internal standards. Calibration curves were linear (r(2)>0.99) in the tested ranges. The lower limit of quantification of analytes in umbilical cord plasma samples is <0.72 ng/mL and 0.92 ng/g in placental tissue samples. The relative deviation of this method was <15% for intra- and inter-day assays, and the accuracy ranged between 88% and 105%. The extraction recovery of the four analytes ranged between 89% and 96% in umbilical cord plasma, and 64% and 80% in placental tissue. No significant matrix effect was observed in the presented method., (Copyright © 2012 Elsevier B.V. All rights reserved.)

Introduction: Although the antidepressant bupropion is prescribed to aid in smoking cessation, little is known concerning its mechanisms of action in this regard. One factor that might influence quit success is nicotine tolerance, which could promote high levels of nicotine intake in order to maintain nicotine's subjective effects (thereby making attempts to reduce smoking more difficult)., Methods: To explore whether bupropion and its active hydroxymetabolite modulate nicotine tolerance, mice were injected for 14 days with saline or nicotine. On Day 14, animals received saline, (2S,3S)-hydroxybupropion, or bupropion at different doses. On Day 15, mice were assayed on test day for nicotine-induced analgesia and hypothermia., Results: Animals chronically injected with saline + nicotine developed tolerance to nicotine's effects in both assays. Administration of bupropion and (2S,3S)-hydroxybupropion dose-dependently reversed chronic nicotine tolerance., Conclusions: These results indicate that bupropion's ability to promote smoking cessation may be partly due to its attenuation of nicotine tolerance since both measured responses of nicotine (antinociception and hypothermia) are mediated to a large extent by neuronal α4β2* nicotine receptors.

Crystal phase transition and isothermal crystallization kinetics of bupropion hydrobromide is studied by thermal analysis, X-ray powder diffractometry, and scanning electron microscopy. As well known, bupropion hydrobromide has two stable polymorphic forms, form I and form II, during the production. Here it is found that form II will convert into form I with thermal treatment. Avrami exponent n is evaluated to be around 2.0 in the range 170°C-190°C, which indicates that the phase transition is a process of one-dimensional nucleation growth. This viewpoint is also confirmed by microscope morphology study. In addition, phase-transition active energy is calculated to be 239.4 kJ/mol, which means that a high energy barrier needs to be overcome to start up the phase transition., (Copyright © 2011 Wiley Periodicals, Inc.)

Introduction: Despite the widespread use of mentholated cigarettes, lower cessation rates, and disproportionately high smoking-related morbidity among Blacks, the possible role of menthol in smokers' response to pharmacotherapy has not been well-studied. This study examined the effects of menthol on the pharmacokinetic (PK) profiles of bupropion and its principal metabolites, hydroxybupropion, threohydrobupropion, and erythrohydrobupropion among Black smokers., Methods: After a 7-day placebo run-in period, participants received 150 mg bid sustained-release bupropion for 20-25 days. Blood samples were drawn for PK analysis on 2 occasions, 10-15 days after the commencement of bupropion while participants were still smoking (smoking phase) and at days 20-25 when they were asked not to smoke (nonsmoking phase)., Results: 18 smokers of nonmenthol cigarettes and 23 smokers of menthol cigarettes were enrolled in this study. No differences were found by menthol smoking status in the Cmax and area under the plasma concentration versus time curve (AUC) of bupropion and its metabolites in the smoking or nonsmoking phases. However, among menthol smokers, the AUC ratios of metabolite/bupropion were lower in the nonsmoking phase compared with the smoking phase (hydro/bup = 31.49 ± 18.84 vs. 22.95 ± 13.27, p = .04; erythro/bup = 1.99 ± 1.02 vs. 1.76 ± 0.75, p = .016; threo/bup = 11.77 ± 8.90 vs. 10.44 ± 5.63, p = .034). No significant differences were found in the metabolite/bup ratios between smoking and nonsmoking conditions among nonmenthol smokers., Conclusions: We did not find a significant effect of menthol compared with nonmenthol cigarette smoking on the PKs of bupropion and metabolites at steady state. More research is needed to advance the understanding of mechanisms underlying disparities in smoking cessation outcomes related to smoking of menthol cigarettes.

Bupropion, a clinically used antidepressant and smoking-cessation drug, acts as a noncompetitive antagonist of nicotinic acetylcholine receptors (nAChRs). To identify its binding site(s) in nAChRs, we developed a photoreactive bupropion analogue, (±)-2-(N-tert-butylamino)-3'-[(125)I]-iodo-4'-azidopropiophenone (SADU-3-72). Based on inhibition of [(125)I]SADU-3-72 binding, SADU-3-72 binds with high affinity (IC(50) = 0.8 μM) to the Torpedo nAChR in the resting (closed channel) state and in the agonist-induced desensitized state, and bupropion binds to that site with 3-fold higher affinity in the desensitized (IC(50) = 1.2 μM) than in the resting state. Photolabeling of Torpedo nAChRs with [(125)I]SADU-3-72 followed by limited in-gel digestion of nAChR subunits with endoproteinase Glu-C established the presence of [(125)I]SADU-3-72 photoincorporation within nAChR subunit fragments containing M1-M2-M3 helices (αV8-20K, βV8-22/23K, and γV8-24K) or M1-M2 helices (δV8-14). Photolabeling within βV8-22/23K, γV8-24K, and δV8-14 was reduced in the desensitized state and inhibited by ion channel blockers selective for the resting (tetracaine) or desensitized (thienycyclohexylpiperidine (TCP)) state, and this pharmacologically specific photolabeling was localized to the M2-9 leucine ring (δLeu(265), βLeu(257)) within the ion channel. In contrast, photolabeling within the αV8-20K was enhanced in the desensitized state and not inhibited by TCP but was inhibited by bupropion. This agonist-enhanced photolabeling was localized to αTyr(213) in αM1. These results establish the presence of two distinct bupropion binding sites within the Torpedo nAChR transmembrane domain: a high affinity site at the middle (M2-9) of the ion channel and a second site near the extracellular end of αM1 within a previously described halothane (general anesthetic) binding pocket.

A sensitive, selective and rapid liquid chromatography tandem mass spectrometry (LC-MS/MS) method was developed for the simultaneous determination of bupropion (BUP) and its major active metabolite hydroxybupropion (HBUP) in human plasma. Separation of both the analytes and venlafaxine as internal standard (IS) from 50 μL human plasma was carried out by solid-phase extraction. The chromatographic separation of the analytes was achieved on a Zorbax Eclipse XDB C(18) (150 × 4.6 mm, 5 µm) analytical column using isocratic mobile phase consisting of 20 mm ammonium acetate-methanol (10:90, v/v), with a resolution factor of 3.5. The method was validated over a wide dynamic concentration range of 0.1-350 ng/mL for BUP and 0.1-600 ng/mL for HBUP. The matrix effect was assessed by post-column infusion and the mean process efficiency was 96.08 and 94.40% for BUP and HBUP, respectively. The method was successfully applied to a bioequivalence study of 150 mg BUP (test and reference) extended release tablet formulation in 12 healthy Indian male subjects under fed conditions., (Copyright © 2011 John Wiley & Sons, Ltd.)

Sertraline potently inhibits cytochrome P450 2B6 (CYP2B6) in vitro. Bupropion is commonly co-prescribed with sertraline and is exclusively metabolized by CYP2B6 to its major active metabolite hydroxybupropion. Putatively the co-administration of bupropion and sertraline could lead to a significant pharmacokinetic drug-drug interaction. The aim of this study was to evaluate a possible drug interaction between these drugs in mice. To study this male CF-1 mice were administered sertraline 5 mg/kg once daily for 6 days, followed by a single dose of bupropion 50 mg/kg on the seventh study day. Plasma and brain samples were collected post-bupropion dose for measurement of bupropion and hydroxybupropion levels on HPLC. Pharmacokinetic parameters for bupropion and hydroxybupropion were calculated using noncompartmental analysis and the variance in AUC of each was computed using Bailer's analysis. We found that mice pretreated with sertraline exhibited a small elevation in bupropion metabolism. This was substantiated by Bailer's analysis which indicated that in the presence of sertraline, both plasma and brain bupropion exposure were significantly (p < 0.05) decreased, while plasma hydroxybupropion exposure was significantly (p < 0.05) increased. Also the plasma hydroxybupropion-to-bupropion ratio of AUC was increased by 27% in sertraline treated mice, indicative of increased CYP2B activity. This is the first study, to our knowledge, that reports a mild pharmacokinetic drug-drug interaction between bupropion and sertraline in mice. However, it is unknown whether these quantitative changes in enzyme activity and consequent drug exposure would equate to significant pharmacodynamic changes (e.g., perturbations in brain neurotransmitter levels) observed in the clinic.

Towards addressing the knowledge gap of how bupropion interacts with the dopamine transporter (DAT) and nicotinic acetylcholine receptors (nAChRs), a ligand was synthesized in which the chlorine of bupropion was isosterically replaced with an iodine and a photoreactive azide was added to the 4'-position of the aromatic ring. Analog (±)-3 (SADU-3-72) demonstrated modest DAT and α4β2 nAChR affinity. A radioiodinated version was shown to bind covalently to hDAT expressed in cultured cells and affinity-purified, lipid-reincorporated human α4β2 neuronal nAChRs. Co-incubation of (±)-[(125)I]-3 with non-radioactive (±)-bupropion or (-)-cocaine blocked labeling of these proteins. Compound (±)-[(125)I]-3 represents the first successful example of a DAT and nAChR photoaffinity ligand based on the bupropion scaffold. Such ligands are expected to assist in mapping bupropion-binding pockets within plasma membrane monoamine transporters and ligand-gated nAChR ion channels., (Copyright © 2011 Elsevier Ltd. All rights reserved.)

A sensitive and selective liquid chromatograpy-mass spectrometry method for the determination of bupropion and its main metabolite, hydroxubupropion, in rat plasma was developed and validated. After addition of carbamazepine as internal standard (IS) and precipitation of protein with acetonitrile, the plasma samples were analyzed on an Agilent Zorbax SB-C18 (2.1 mm x 50 mm, 3.5 microm) column at 30 degrees C, with acetonitrile-0.1% formic acid as mobile phase at a flow rate of 0.4 mL min(-1). The detection was carried out in the selective ion monitoring mode with a positive electrospray ionization interface. The calibration curve was linear over the 10-2000 ng mL(-1) for bupropion and 5-1000 ng mL(-1) for hydroxybupropion in plasma. RSD of inter-day and intra-day precision was less than 7% for bupropion, 9% for hydroxybupropion. The developed method was successfully applied to pharmacokinetic studies after single intragastric administration of bupropion 15 mg kg(-1) to rats.

Intravenous fat emulsion (IFE) is emerging as a novel antidote in clinical toxicology. Its current usage is extending beyond local anaesthetic toxicity into management of severe toxicity from some lipophilic drugs. We present a 51-year-old woman with severe bupropion toxicity whose haemodynamic status transiently improved after IFE. Serum analysis demonstrated an increase in serum concentration of hydroxybupropion, an active metabolite of bupropion, after IFE administration, lending support to one of the proposed mechanisms of IFE. A 51-year-old woman presented to the emergency department with generalised tonic-clonic convulsions lasting approximately 30 sec., and a wide complex rhythm on her ECG that was suggestive of myocardial sodium channel blockade. Despite sodium bicarbonate therapy, the patient developed profound hypotension refractory to high-dose norepinephrine. IFE was administered with haemodynamic improvement over the course of 30 min., followed by a significant decrease in norepinephrine requirement. The patient had an episode of ventricular tachycardia 24 hr after presentation, and received a second infusion of IFE. Analysis of serum for a panel of myocardial sodium channel blocking drugs revealed that significant bupropion ingestion had occurred. Bupropion poisoning may produce life-threatening clinical effects, and IFE may be considered in cases of severe haemodynamic instability. Further studies would be instrumental in determining the optimal clinical situations for utilisation of IFE., (© 2011 The Authors. Basic & Clinical Pharmacology & Toxicology © 2011 Nordic Pharmacological Society.)

The atypical antidepressant, bupropion, causes a partial reversal of motor deficits in 1-methyl-4-phenyl-1,2,3,6-tetrahydropyridine-treated primates. However, its monoamine uptake blocking actions are believed to be mediated by the major metabolites, racemic (-)-(2R,3R)-2-(3-chlorophenyl-3,5,5-trimethyl-2-morphinol) (R,R-hydroxybupropion) and (+)-(2S,3S)-2-(3-chlorophenyl-3,5,5-trimethyl-2-morphinol) (S,S-hydroxybupropion). Therefore, we have evaluated the ability of enantiomers to improve locomotor activity and motor disability in 1-methyl-4-phenyl-1,2,3,6-tetrahydropyridine-treated common marmosets. Bupropion produced a little increase in locomotor activity and a more pronounced improvement in motor disability. The S,S-hydroxybupropion, but not the R,R-hydroxybupropion, enantiomer dose-dependently increased both locomotor activity and reversed motor disability. Combined administration of S,S-hydroxybupropion and R,R-hydroxybupropion at the same dose (analogous to the racemate) again improved motor function and to the same extent as produced by S,S-hydroxybupropion alone. The data suggest that the S,S-enantiomer of hydroxybupropion may possess potential antiparkinsonian activity.

A specific and highly sensitive liquid chromatography-electrospray mass spectrometry (LC-ESI-MS) method for the direct determination of bupropion (BUP) and its main metabolite hydroxybupropion (HBUP) in rat plasma and brain microdialysate has been developed and validated. The analysis was performed on a Bonus RP C18 (100 mm × 2.1mm i.d., 3.5 μm particles) column using gradient elution with the mobile phase consisting of acetonitrile and ammonium formate buffer (10mM, pH 4). Plasma samples were analyzed after a simple, one-step protein precipitation clean-up with trichloroacetic acid (TCA), however clean-up for microdialysis samples was not necessary, enabling direct injection of the samples into the LC-ESI-MS system. Signals of the compounds were monitored under the multiple reaction monitoring (MRM) mode of the LC-ESI-MS (ion trap) for quantification. The precursor to product ion transitions of m/z 240-184 and m/z 256-238 were used to measure BUP and HBUP, respectively. The method was validated in both plasma and microdialysate samples, and the obtained lower limit of quantification (LLOQ) was 1.5 ng mL(-1) for BUP and HBUP in both matrices. The intra- and inter-day assay variability was less than 15% for both analytes. This LC-ESI-MS method provided simple sampling, rapid clean-up and short analysis time (<9 min), applicable to the routine therapeutic monitoring and pharmacokinetic studies of BUP and HBUP., (Copyright © 2010 Elsevier B.V. All rights reserved.)

We investigated genetic polymorphisms in the pregnane X receptor (NR1I2) in Korean individuals (n = 83) and the effects of NR1I2 genotypes on rifampin-mediated induction of bupropion hydroxylation. The pharmacokinetics of bupropion and hydroxybupropion were evaluated after an oral dose of bupropion (150 mg) administered before and after rifampin treatment for 7 days in 35 healthy subjects. The area under the time-concentration curve (AUC) ratio of hydroxybupropion to bupropion in CYP2B6*6 carriers was significantly lower than that in CYP2B6*6 noncarriers in both the basal and rifampin-induced states (p = 0.012). Among the CYP2B6*6 carriers (n = 13), the NR1I2 TGT (-25385T + g.7635G + g.8055T) carriers exhibited a significantly lower AUC ratio, representing the CYP2B6 hydroxylation activity, compared with the TGT noncarriers, in the induced state (11.9 versus 20.3, p = 0.045). The percent difference in the AUC ratio between the basal and induced states was also significantly different (212% versus 58.8%, p = 0.006). However, no significant difference was observed among the NR1I2 TGT genotypes for the CYP2B6*6 noncarriers (n = 22). In conclusion, it is suggested the NR1I2 TGT genotype decreases the bupropion hydroxylation induced by treatment with rifampin, particularly in CYP2B6*6 carriers.

Bupropion is an atypical antidepressant that also has utility as a smoking cessation aid. Hydroxybupropions are major metabolites of bupropion and are believed to contribute to antidepressant and perhaps smoking cessation activities. Because bupropion metabolism is more similar in humans and mice than in humans and rats, the present study investigated effects of hydroxybupropion enantiomers in mouse behavioral models measuring various aspects of nicotine dependence. Bupropion and (2S,3S)-hydroxybupropion, but not (2R,3R)-hydroxybupropion, significantly decreased the development of nicotine reward as measured in the conditioned place preference and withdrawal paradigm in mice. Bupropion and both of its metabolites reversed affective and somatic withdrawal signs in nicotine-dependent mice, but the (2S,3S)-hydroxymetabolite had higher potency. Bupropion and (2S,3S)-, but not (2R,3R)-hydroxybupropion, produced partial substitution for nicotine in drug discrimination tests. Our findings support the hypothesis that the effects of bupropion on measures of nicotine dependence reflect actions of bupropion itself, its hydroxymetabolites, or a combination and suggest that the (2S,3S)-hydroxy isomer is the most active principle, making it a potentially better drug candidate for smoking cessation than bupropion.