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Evan D Kharasch - One of the best experts on this subject based on the ideXlab platform.
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stereoselective bupropion hydroxylation by cytochrome p450 cyp2b6 and cytochrome p450 oxidoreductase genetic variants
Drug Metabolism and Disposition, 2020Co-Authors: Panfen Wang, Alicia Neiner, Evan D KharaschAbstract:Bioactivation of the antidepressant and smoking cessation drug bupropion is catalyzed predominantly by CYP2B6. The metabolite Hydroxybupropion derived from t-butylhydroxylation is considered to contribute to the antidepressant and smoking-cessation effects of the parent drug. Bupropion hydroxylation is the canonical in vitro and in vivo probe for CYP2B6 activity. P450 also requires obligate partnership with P450 oxidoreductase (POR). Human CYP2B6 and POR genes are highly polymorphic. Some CYP2B6 variants affect bupropion disposition. This investigation evaluated the influence of several human CYP2B6 and POR genetic variants on stereoselective bupropion metabolism, using an insect cell coexpression system containing CYP2B6, POR, and cytochrome b5. Based on intrinsic clearances (Clints), relative activities for S,S-Hydroxybupropion formation were in the order CYP2B6.4 > CYP2B6.1 > CYP2B6.17 > CYP2B6.5 > CYP2B6.6 ≈ CYP2B6.26 ≈ CYP2B6.19 > CYP2B6.7 > CYP2B6.9 > > CYP2B6.16 and CYP2B6.18; relative activities for R,R-Hydroxybupropion formation were in the order CYP2B6.17 > CYP2B6.4 > CYP2B6.1 > CYP2B6.5 ≈ CYP2B6.19 ≈ CYP2B6.26 > CYP2B6.6 > CYP2B6.7 ≈ CYP2B6.9 > > CYP2B6.16 and CYP2B6.18. Bupropion hydroxylation was not influenced by POR variants. CYP2B6-catalyzed bupropion hydroxylation is stereoselective. Though Vmax and Km varied widely among CYP2B6 variants, stereoselectivity was preserved, reflected by similar Clint(S,S-Hydroxybupropion)/Clint(R,R-Hydroxybupropion) ratios (1.8–2.9), except CYP2B6.17, which was less enantioselective. Established concordance between human bupropion hydroxylation in vitro and in vivo, together with these new results, suggests additional CYP2B6 variants may influence human bupropion disposition. SIGNIFICANCE STATEMENT Bupropion pharmacokinetics, metabolism, and clinical effects are affected by the CYP2B6*6 polymorphism. Other expressed CYP2B6 polymorphisms had diminished (*5, *6, *7, *9, *19, *26) or defective (*16, *18) in vitro bupropion hydroxylation. P450 oxidoreductase genetic variants had no effect on metabolism, suggesting no clinical consequence of this polymorphism. These CYP2B6 polymorphisms may portend diminished in vivo bupropion hydroxylation and predict additional clinically important variant alleles.
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common polymorphisms of cyp2b6 influence stereoselective bupropion disposition
Clinical Pharmacology & Therapeutics, 2019Co-Authors: Evan D Kharasch, Amanda CraffordAbstract:Bupropion hydroxylation is a bioactivation and metabolic pathway, and the standard clinical CYP2B6 probe. This investigation determined the influence of CYP2B6 allelic variants on clinical concentrations and metabolism of bupropion enantiomers. Secondary objectives evaluated the influence of CYP2C19 and P450 oxidoreductase variants. Healthy volunteers in specific cohorts (CYP2B6*1/*1, CYP2B6*1/*6, CYP2B6*6/*6, and also CYP2B6*4 carriers) received single-dose oral bupropion. Plasma and urine bupropion and Hydroxybupropion was quantified. Subjects were also genotyped for CYP2C19 and P450 oxidoreductase variants. Hydroxylation of both bupropion enantiomers, assessed by plasma Hydroxybupropion/bupropion AUC ratios and urine Hydroxybupropion formation clearances, was lower in CYP2B6*6/*6 but not CYP2B6*1/*6 compared with CYP2B6*1/*1 genotypes, and numerically greater in CYP2B6*4 carriers. CYP2C19 and P450 oxidoreductase variants did not influence bupropion enantiomers hydroxylation or plasma concentrations. The results show that clinical hydroxylation of both bupropion enantiomers was equivalently influenced by CYP2B6 allelic variation. CYP2B6 polymorphisms affect S-bupropion bioactivation, which may affect therapeutic outcomes.
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stereoselective bupropion hydroxylation as an in vivo phenotypic probe for cytochrome p4502b6 cyp2b6 activity
The Journal of Clinical Pharmacology, 2008Co-Authors: Evan D Kharasch, Darain Mitchell, Rebecka ColesAbstract:The clearance of racemic bupropion, metabolized selectively by CYP2B6 in vitro, has been used clinically to phenotype CYP2B6 activity, polymorphisms, and drug interactions but has known limitations. Bupropion hydroxylation by CYP2B6 is stereoselective. This investigation assessed the stereoselectivity of bupropion pharmacokinetics and the influence of CYP2B6 induction. Ten healthy volunteers received immediate-release bupropion before and after 7 days of rifampin. Plasma and urine bupropion and Hydroxybupropion were analyzed using a stereoselective assay. Plasma area under the curve (AUC(0-infinity)) and maximum concentrations were 3-fold greater for R- than S-bupropion. Bupropion apparent oral clearance was 3- and 2-fold greater for S- than R- and R,S-bupropion, respectively. Hydroxybupropion plasma AUC(0-infinity) and elimination half-life were significantly less for (S,S)- than (R,R)- and the racemate. (S,S)-Hydroxybupropion was formation rate limited, whereas (R,R)-Hydroxybupropion and the racemate were elimination rate limited. Rifampin doubled both R- and S-bupropion clearance and caused 4-fold increases in both (R,R)- and (S,S)-Hydroxybupropion formation clearances. Increases in the plasma Hydroxybupropion/bupropion AUC(0-infinity) ratio were greater for (S,S)- than (R,R)-Hydroxybupropion. Simplified plasma and urine metrics of stereoselective bupropion metabolism and clearance were identified. Because metabolite formation clearance is the best in vivo metric of enzyme activity and due, therefore, to faster S-bupropion elimination and formation rate-limited (S,S)-Hydroxybupropion kinetics, stereoselective S-bupropion hydroxylation and (S,S)-Hydroxybupropion formation clearance may be a useful and improved phenotypic probe for CYP2B6.
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Rapid clinical induction of hepatic cytochrome P4502B6 activity by ritonavir.
Antimicrobial agents and chemotherapy, 2008Co-Authors: Evan D Kharasch, Darain Mitchell, Rebecka Coles, Roberto BlancoAbstract:Ritonavir is the most potent and efficacious inhibitor of cytochrome P4503A (CYP3A), and it is used accordingly for the pharmacoenhancement of other antiretrovirals. Paradoxically, ritonavir induces the clinical metabolism and clearance of many drugs. The mechanism by which ritonavir inhibits and induces clinical drug metabolism is unknown. Ritonavir induces CYP2B6 in human hepatocytes. This investigation tested the hypothesis that ritonavir induces human CYP2B6 in vivo. Thirteen healthy human immunodeficiency virus-negative volunteers underwent a three-way sequential crossover protocol, receiving racemic bupropion after nothing (control), 3 days of treatment with ritonavir, and 2.5 weeks of treatment with ritonavir (400 mg twice a day). Stereoselective bupropion hydroxylation was used as an in vivo probe for CYP2B6 activity. Plasma and urine (R)- and (S)-bupropion and (R,R)- and (S,S)-Hydroxybupropion concentrations were measured by liquid chromatography-mass spectrometry. Racemic, (R)-, and (S)-bupropion plasma ratios of the area under the concentration-time curve from 0 h to infinity (AUC0-∞) (ritonavir/control) were significantly reduced to 0.84, 0.86, and 0.80, respectively, after 3 days of ritonavir treatment and to 0.67, 0.69, and 0.60 after steady-state ritonavir treatment. Apparent oral clearances for racemic, (R)-, and (S)-bupropion all were significantly increased by 1.2-fold after 3 days of ritonavir treatment and by 1.4-, 1.7-, and 1.5-fold after steady-state ritonavir treatment. The plasma (S,S)-Hydroxybupropion/(S)-bupropion AUC0-72 ratio was significantly increased by ritonavir. Formation clearances of both (R,R)- and (S,S)-Hydroxybupropion were increased 1.8-fold after 3 days of ritonavir treatment and 2.1-fold after steady-state ritonavir treatment. These results show that ritonavir induces human CYP2B6 activity. Induction is rapid, occurring after only 3 days of ritonavir, and is sustained for at least 2 weeks. The ritonavir induction of CYP2B6 activity may have significant implications for drug interactions and clarify previously unexplained interactions.
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stereoselective analysis of bupropion and Hydroxybupropion in human plasma and urine by lc ms ms
Journal of Chromatography B, 2007Co-Authors: Rebecka Coles, Evan D KharaschAbstract:A sensitive, stereoselective assay using solid phase extraction and LC-MS-MS was developed and validated for the analysis of (R)- and (S)-bupropion and its major metabolite (R,R)- and (S,S)-Hydroxybupropion in human plasma and urine. Plasma or glucuronidase-hydrolyzed urine was acidified, then extracted using a Waters Oasis MCX solid phase 96-well plate. HPLC separation used an alpha(1)-acid glycoprotein column, a gradient mobile phase of methanol and aqueous ammonium formate, and analytes were detected by electrospray ionization and multiple reaction monitoring with an API 4000 Qtrap. The assay was linear in plasma from 0.5 to 200 ng/ml and 2.5 to 1000 ng/ml in each bupropion and Hydroxybupropion enantiomer, respectively. The assay was linear in urine from 5 to 2000 ng/ml and 25 to 10,000 ng/ml in each bupropion and Hydroxybupropion enantiomer, respectively. Intra- and inter-day accuracy was >98% and intra- and inter-day coefficients of variations were less than 10% for all analytes and concentrations. The assay was applied to a subject dosed with racemic bupropion. The predominant enantiomers in both urine and plasma were (R)-bupropion and (R,R)-Hydroxybupropion. This is the first LC-MS/MS assay to analyze the enantiomers of both bupropion and Hydroxybupropion in plasma and urine.
Rebecka Coles - One of the best experts on this subject based on the ideXlab platform.
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stereoselective bupropion hydroxylation as an in vivo phenotypic probe for cytochrome p4502b6 cyp2b6 activity
The Journal of Clinical Pharmacology, 2008Co-Authors: Evan D Kharasch, Darain Mitchell, Rebecka ColesAbstract:The clearance of racemic bupropion, metabolized selectively by CYP2B6 in vitro, has been used clinically to phenotype CYP2B6 activity, polymorphisms, and drug interactions but has known limitations. Bupropion hydroxylation by CYP2B6 is stereoselective. This investigation assessed the stereoselectivity of bupropion pharmacokinetics and the influence of CYP2B6 induction. Ten healthy volunteers received immediate-release bupropion before and after 7 days of rifampin. Plasma and urine bupropion and Hydroxybupropion were analyzed using a stereoselective assay. Plasma area under the curve (AUC(0-infinity)) and maximum concentrations were 3-fold greater for R- than S-bupropion. Bupropion apparent oral clearance was 3- and 2-fold greater for S- than R- and R,S-bupropion, respectively. Hydroxybupropion plasma AUC(0-infinity) and elimination half-life were significantly less for (S,S)- than (R,R)- and the racemate. (S,S)-Hydroxybupropion was formation rate limited, whereas (R,R)-Hydroxybupropion and the racemate were elimination rate limited. Rifampin doubled both R- and S-bupropion clearance and caused 4-fold increases in both (R,R)- and (S,S)-Hydroxybupropion formation clearances. Increases in the plasma Hydroxybupropion/bupropion AUC(0-infinity) ratio were greater for (S,S)- than (R,R)-Hydroxybupropion. Simplified plasma and urine metrics of stereoselective bupropion metabolism and clearance were identified. Because metabolite formation clearance is the best in vivo metric of enzyme activity and due, therefore, to faster S-bupropion elimination and formation rate-limited (S,S)-Hydroxybupropion kinetics, stereoselective S-bupropion hydroxylation and (S,S)-Hydroxybupropion formation clearance may be a useful and improved phenotypic probe for CYP2B6.
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Rapid clinical induction of hepatic cytochrome P4502B6 activity by ritonavir.
Antimicrobial agents and chemotherapy, 2008Co-Authors: Evan D Kharasch, Darain Mitchell, Rebecka Coles, Roberto BlancoAbstract:Ritonavir is the most potent and efficacious inhibitor of cytochrome P4503A (CYP3A), and it is used accordingly for the pharmacoenhancement of other antiretrovirals. Paradoxically, ritonavir induces the clinical metabolism and clearance of many drugs. The mechanism by which ritonavir inhibits and induces clinical drug metabolism is unknown. Ritonavir induces CYP2B6 in human hepatocytes. This investigation tested the hypothesis that ritonavir induces human CYP2B6 in vivo. Thirteen healthy human immunodeficiency virus-negative volunteers underwent a three-way sequential crossover protocol, receiving racemic bupropion after nothing (control), 3 days of treatment with ritonavir, and 2.5 weeks of treatment with ritonavir (400 mg twice a day). Stereoselective bupropion hydroxylation was used as an in vivo probe for CYP2B6 activity. Plasma and urine (R)- and (S)-bupropion and (R,R)- and (S,S)-Hydroxybupropion concentrations were measured by liquid chromatography-mass spectrometry. Racemic, (R)-, and (S)-bupropion plasma ratios of the area under the concentration-time curve from 0 h to infinity (AUC0-∞) (ritonavir/control) were significantly reduced to 0.84, 0.86, and 0.80, respectively, after 3 days of ritonavir treatment and to 0.67, 0.69, and 0.60 after steady-state ritonavir treatment. Apparent oral clearances for racemic, (R)-, and (S)-bupropion all were significantly increased by 1.2-fold after 3 days of ritonavir treatment and by 1.4-, 1.7-, and 1.5-fold after steady-state ritonavir treatment. The plasma (S,S)-Hydroxybupropion/(S)-bupropion AUC0-72 ratio was significantly increased by ritonavir. Formation clearances of both (R,R)- and (S,S)-Hydroxybupropion were increased 1.8-fold after 3 days of ritonavir treatment and 2.1-fold after steady-state ritonavir treatment. These results show that ritonavir induces human CYP2B6 activity. Induction is rapid, occurring after only 3 days of ritonavir, and is sustained for at least 2 weeks. The ritonavir induction of CYP2B6 activity may have significant implications for drug interactions and clarify previously unexplained interactions.
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stereoselective analysis of bupropion and Hydroxybupropion in human plasma and urine by lc ms ms
Journal of Chromatography B, 2007Co-Authors: Rebecka Coles, Evan D KharaschAbstract:A sensitive, stereoselective assay using solid phase extraction and LC-MS-MS was developed and validated for the analysis of (R)- and (S)-bupropion and its major metabolite (R,R)- and (S,S)-Hydroxybupropion in human plasma and urine. Plasma or glucuronidase-hydrolyzed urine was acidified, then extracted using a Waters Oasis MCX solid phase 96-well plate. HPLC separation used an alpha(1)-acid glycoprotein column, a gradient mobile phase of methanol and aqueous ammonium formate, and analytes were detected by electrospray ionization and multiple reaction monitoring with an API 4000 Qtrap. The assay was linear in plasma from 0.5 to 200 ng/ml and 2.5 to 1000 ng/ml in each bupropion and Hydroxybupropion enantiomer, respectively. The assay was linear in urine from 5 to 2000 ng/ml and 25 to 10,000 ng/ml in each bupropion and Hydroxybupropion enantiomer, respectively. Intra- and inter-day accuracy was >98% and intra- and inter-day coefficients of variations were less than 10% for all analytes and concentrations. The assay was applied to a subject dosed with racemic bupropion. The predominant enantiomers in both urine and plasma were (R)-bupropion and (R,R)-Hydroxybupropion. This is the first LC-MS/MS assay to analyze the enantiomers of both bupropion and Hydroxybupropion in plasma and urine.
Honghao Zhou - One of the best experts on this subject based on the ideXlab platform.
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genetic variants of pregnane x receptor pxr and cyp2b6 affect the induction of bupropion hydroxylation by sodium ferulate
PLOS ONE, 2013Co-Authors: Lichen Gao, Xiaoping Chen, Jie Tang, Jiye Yin, Zhengyu Huang, Fangqun Liu, Dongsheng Ouyang, Wei Zhang, Zhaoqian Liu, Honghao ZhouAbstract: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_hyd (AUC(0-∞) of Hydroxybupropion)/AUC_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_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.
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rapid clinical induction of bupropion hydroxylation by metamizole in healthy chinese men
British Journal of Clinical Pharmacology, 2012Co-Authors: Xiaoping Chen, Dongli Hu, Dan Wang, Honghao ZhouAbstract:WHAT IS ALREADY KNOWN ABOUT THIS SUBJECT • Bupropion, an antidepressant and smoking cessation drug, is metabolized to its active metabolite, 4-Hydroxybupropion, almost exclusively by CYP2B6. • Metamizole, a pyrazolone derivative with analgesic properties, was shown in an in vitro study to increase significantly the expression of CYP2B6 and bupropion hydroxylase activity. • The effect of metamizole on bupropion hydroxylation has not been investigated and drug interactions may occur between metamizole and bupropion. WHAT THIS PAPER ADDS • Oral administration of metamizole for 4 days significantly altered the pharmacokinetics of both bupropion and its active metabolite, 4-Hydroxybupropion, and significantly increased the CYP2B6-catalyzed bupropion hydroxylation in all of the subjects. • Dosage adjustment of bupropion may be needed in patients when metamizole is concomitantly administered. AIMS This study aimed to investigate the effect of metamizole on bupropion hydroxylation related to different CYP2B6 genotype groups in healthy volunteers. METHODS Sixteen healthy male volunteers (6 CYP2B6*1/*1, 6 CYP2B6*1/*6 and 4 CYP2B6*6/*6) received orally administered bupropion alone and during daily treatment with metamizole 1500 mg day–1 (500 mg tablet taken three times daily) for 4 days. Serial blood samples were obtained up to 48 h after each bupropion dose. RESULTS After metamizole treatment relative to bupropion alone, the geometric mean ratios (GMRs) and 90% confidence interval (CI) of the AUC(0,∞) ratio of 4-Hydroxybupropion over bupropion were 1.99 (1.57, 2.55) for the CYP2B6*1/*1 group, 2.15 (1.53, 3.05) for the CYP2B6*1/*6 group and 1.86 (1.36, 2.57) for the CYP2B6*6/*6 group. The GMRs and 90% CI of bupropion were 0.695 (0.622, 0.774) for AUC(0,∞) and 0.400 (0.353, 0.449) for Cmax, respectively. The corresponding values for 4-Hydroxybupropion were 1.43 (1.28, 1.53) and 2.63 (2.07, 2.92). The t1/2 value was significantly increased for bupropion and decreased for 4-Hydroxybupropion. The tmax values of bupropion and 4-Hydroxybupropion were both significantly decreased. The mean percentage changes in pharmacokinetic parameters among the CYP2B6 genotype groups were not significantly different. CONCLUSIONS Oral administration of metamizole for 4 days significantly altered the pharmacokinetics of both bupropion and its active metabolite, 4-Hydroxybupropion, and significantly increased the CYP2B6-catalyzed bupropion hydroxylation in all of the subjects. Cautions should be taken when metamizole is co-administered with CYP2B6 substrate drugs.
Olavi Pelkonen - One of the best experts on this subject based on the ideXlab platform.
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effect of clopidogrel and ticlopidine on cytochrome p450 2b6 activity as measured by bupropion hydroxylation
Clinical Pharmacology & Therapeutics, 2005Co-Authors: Miia Turpeinen, Olavi Pelkonen, Jouko Uusitalo, Ari Tolonen, Jorma JalonenAbstract:Objective Our objective was to study the effect of the antiplatelet agents clopidogrel and ticlopidine on bupropion (INN, amfebutamone) hydroxylation, a probe reaction for cytochrome P450 (CYP) 2B6 activity. Methods Twelve healthy male volunteers took a single 150-mg oral dose of bupropion either alone or after pretreatment with 75 mg clopidogrel once daily or 250 mg ticlopidine twice daily for 4 days. On day 4, a single 150-mg oral dose of bupropion was administered. Plasma concentrations of bupropion and its CYP2B6-catalyzed metabolite, Hydroxybupropion, were measured for up to 72 hours. Results The mean area under the plasma concentration-time curve (AUC) of Hydroxybupropion calculated from time 0 to infinity was reduced by 52% (P = .001; 95% confidence interval [CI], 39% to 66%) by clopidogrel and by 84% (P < .0001; 95% CI, 73% to 94%) by ticlopidine. Clopidogrel reduced the AUC ratio of Hydroxybupropion over bupropion by 68% (P = .002; 95% CI, 58% to 77%) and ticlopidine by 90% (P = .001; 95% CI, 85% to 96%). The AUC of bupropion was increased by 60% (P = .02; 95% CI, 21% to 98%) and by 85% (P < .0001; 95% CI, 48% to 85%) with clopidogrel and ticlopidine, respectively. Conclusions Both clopidogrel and ticlopidine significantly inhibited the CYP2B6-catalyzed bupropion hydroxylation. Patients receiving either clopidogrel or ticlopidine are likely to require dose adjustments when treated with drugs primarily metabolized by CYP2B6. Clinical Pharmacology & Therapeutics (2005) 77, 553–559; doi: 10.1016/j.clpt.2005.02.010
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inhibition of cytochrome p450 2b6 activity by hormone replacement therapy and oral contraceptive as measured by bupropion hydroxylation
Clinical Pharmacology & Therapeutics, 2003Co-Authors: Olavi Pelkonen, Jouko Uusitalo, Sanna Palovaara, Stephan LundgrenAbstract:Aim Our objective was to study the effect of hormone replacement therapy and a combination oral contraceptive on the cytochrome P450 (CYP) 2B6 activity with bupropion (INN, amfebutamone) hydroxylation used as a probe reaction. Methods This was a 3-way crossover study with 12 healthy female volunteers. The first phase was a control phase, in which all subjects received a single 150-mg dose of bupropion (sustained release) without pretreatment. In the second and third phases, in randomized balanced crossover order, subjects received a 10-day pretreatment with either hormone replacement therapy, containing 2 mg estradiol valerate and 250 μg levonorgestrel, or an oral contraceptive, containing 30 μg ethinyl estradiol (INN, ethinylestradiol) and 150 μg desogestrel, and the bupropion dose was given 1 hour after the last hormone dose. The bupropion, Hydroxybupropion, and hydrobupropion plasma concentrations were determined for up to 72 hours. Results The 10-day hormone replacement therapy pretreatment reduced the Hydroxybupropion/bupropion area under the plasma concentration–time curve (AUC) ratio by 49% (P < .001; 95% confidence interval [CI], −58% to −40%) as a result of a marked 47% decrease (P < .001; 95% CI, −54% to −41%) in the AUC of Hydroxybupropion. Moreover, the AUC of hydrobupropion was significantly (64%; P = .003; 95% CI, 22% to 106%) increased. The AUC of Hydroxybupropion was also reduced after the oral contraceptive treatment but to a lesser extent (−31%; P < .001; 95% CI, −37% to −26%). However, the Hydroxybupropion/bupropion AUC ratio was not significantly affected. Conclusions Hormone replacement therapy markedly inhibited the CYP2B6-catalyzed hydroxylation of bupropion, whereas a combination oral contraceptive had only a modest effect on CYP2B6 activity. Patients receiving hormone replacement therapy or oral contraceptives may need dose adjustment when treated with drugs metabolized by CYP2B6. Clinical Pharmacology & Therapeutics (2003) 74, 326–333; doi: 10.1016/S0009-9236(03)00202-9
Zeruesenay Desta - One of the best experts on this subject based on the ideXlab platform.
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chiral plasma pharmacokinetics and urinary excretion of bupropion and metabolites in healthy volunteers
Journal of Pharmacology and Experimental Therapeutics, 2016Co-Authors: Andrea R Masters, Brandon T Gufford, Ingrid F Metzger, David R Jones, Zeruesenay DestaAbstract:Bupropion, widely used as an antidepressant and smoking cessation aid, undergoes complex metabolism to yield numerous metabolites with unique disposition, effect, and drug-drug interactions (DDIs) in humans. The stereoselective plasma and urinary pharmacokinetics of bupropion and its metabolites were evaluated to understand their potential contributions to bupropion effects. Healthy human volunteers (n = 15) were administered a single oral dose of racemic bupropion (100 mg), which was followed by collection of plasma and urine samples and determination of bupropion and metabolite concentrations using novel liquid chromatography-tandem mass spectrometry assays. Time-dependent, elimination rate-limited, stereoselective pharmacokinetics were observed for all bupropion metabolites. Area under the plasma concentration-time curve from zero to infinity ratios were on average approximately 65, 6, 6, and 4 and Cmax ratios were approximately 35, 6, 3, and 0.5 for (2R,3R)-/(2S,3S)-Hydroxybupropion, R-/S-bupropion, (1S,2R)-/(1R,2S)-erythrohydrobupropion, and (1R,2R)-/(1S,2S)-threohydrobupropion, respectively. The R-/S-bupropion and (1R,2R)-/(1S,2S)-threohydrobupropion ratios are likely indicative of higher presystemic metabolism of S- versus R-bupropion by carbonyl reductases. Interestingly, the apparent renal clearance of (2S,3S)-Hydroxybupropion was almost 10-fold higher than that of (2R,3R)-Hydroxybupropion. The prediction of steady-state pharmacokinetics demonstrated differential stereospecific accumulation [partial area under the plasma concentration-time curve after the final simulated bupropion dose (300-312 hours) from 185 to 37,447 nM⋅h] and elimination [terminal half-life of approximately 7-46 hours] of bupropion metabolites, which may explain observed stereoselective differences in bupropion effect and DDI risk with CYP2D6 at steady state. Further elucidation of bupropion and metabolite disposition suggests that bupropion is not a reliable in vivo marker of CYP2B6 activity. In summary, to our knowledge, this is the first comprehensive report to provide novel insight into mechanisms underlying bupropion disposition by detailing the stereoselective pharmacokinetics of individual bupropion metabolites, which will enhance clinical understanding of bupropion's effects and DDIs with CYP2D6.
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stereoselective glucuronidation of bupropion metabolites in vitro and in vivo
Drug Metabolism and Disposition, 2016Co-Authors: Brandon T Gufford, Ingrid F Metzger, David R Jones, Zeruesenay DestaAbstract:Bupropion is a widely used antidepressant and smoking cessation aid in addition to being one of two US Food and Drug Administration–recommended probe substrates for evaluation of cytochrome P450 2B6 activity. Racemic bupropion undergoes oxidative and reductive metabolism, producing a complex profile of pharmacologically active metabolites with relatively little known about the mechanisms underlying their elimination. A liquid chromatography-tandem mass spectrometry assay was developed to simultaneously separate and detect glucuronide metabolites of (R,R)- and (S,S)-Hydroxybupropion, (R,R)- and (S,S)-hydrobupropion (threo) and (S,R)- and (R,S)-hydrobupropion (erythro), in human urine and liver subcellular fractions to begin exploring mechanisms underlying enantioselective metabolism and elimination of bupropion metabolites. Human liver microsomal data revealed marked glucuronidation stereoselectivity [Clint, 11.4 versus 4.3 µl/min per milligram for the formation of (R,R)- and (S,S)-Hydroxybupropion glucuronide; and Clmax, 7.7 versus 1.1 µl/min per milligram for the formation of (R,R)- and (S,S)-hydrobupropion glucuronide], in concurrence with observed enantioselective urinary elimination of bupropion glucuronide conjugates. Approximately 10% of the administered bupropion dose was recovered in the urine as metabolites with glucuronide metabolites, accounting for approximately 40%, 15%, and 7% of the total excreted Hydroxybupropion, erythro-hydrobupropion, and threo-hydrobupropion, respectively. Elimination pathways were further characterized using an expressed UDP-glucuronosyl transferase (UGT) panel with bupropion enantiomers (both individual and racemic) as substrates. UGT2B7 catalyzed the stereoselective formation of glucuronides of Hydroxybupropion, (S,S)-hydrobupropion, (S,R)- and (R,S)-hydrobupropion; UGT1A9 catalyzed the formation of (R,R)-hydrobupropion glucuronide. These data systematically describe the metabolic pathways underlying bupropion metabolite disposition and significantly expand our knowledge of potential contributors to the interindividual and intraindividual variability in therapeutic and toxic effects of bupropion in humans.
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effects of the cyp2b6 6 allele on catalytic properties and inhibition of cyp2b6 in vitro implication for the mechanism of reduced efavirenz metabolism and other cyp2b6 substrates in vivo
Drug Metabolism and Disposition, 2012Co-Authors: Evan T Ogburn, Yingying Guo, Zeruesenay DestaAbstract:The mechanism by which CYP2B6*6 allele alters drug metabolism in vitro and in vivo is not fully understood. To test the hypothesis that altered substrate binding and/or catalytic properties contribute to its functional consequences, efavirenz 8-hydroxylation and bupropion 4-hydroxylation were determined in CYP2B6.1 and CYP2B6.6 proteins expressed without and with cytochrome b5 (Cyt b5) and in human liver microsomes (HLMs) obtained from liver tissues genotyped for the CYP2B6*6 allele. The susceptibility of the variant protein to inhibition was also tested in HLMs. Significantly higher V(max) and K(m) values for 8-hydroxyefavirenz formation and ∼2-fold lower intrinsic clearance (Cl(int)) were noted in expressed CYP2B6.6 protein (-b5) compared with that of CYP2B6.1 protein (-b5); this effect was abolished by Cyt b5. The V(max) and Cl(int) values for 4-Hydroxybupropion formation were significantly higher in CYP2B6.6 than in CYP2B6.1 protein, with no difference in K(m), whereas coexpression with Cyt b5 reversed the genetic effect on these kinetic parameters. In HLMs, CYP2B6*6/*6 genotype was associated with markedly lower V(max) (and moderate increase in K(m)) and thus lower Cl(int) values for efavirenz and bupropion metabolism, but no difference in catalytic properties was noted between CYP2B6*1/*1 and CYP2B6*1/*6 genotypes. Inhibition of efavirenz 8-hydroxylation by voriconazole was significantly greater in HLMs with the CYP2B6*6 allele (K(i) = 1.6 ± 0.8 μM) than HLMs with CYP2B6*1/*1 genotype (K(i) = 3.0 ± 1.1 μM). In conclusion, our data suggest the CYP2B6*6 allele influences metabolic activity by altering substrate binding and catalytic activity in a substrate- and Cyt b5-dependent manner. It may also confer susceptibility to inhibition.
