Chlorzoxazone, a selective probe for phenotyping CYP2E1 in humans

Lucas, Danièle; Ferrara, Roberta; González, Eva; Bodénez, Pierre; Albores, Arnulfo; Manno, Maurizio; Berthou, F.

doi:10.1097/00008571-199906000-00013

Cited by 100 publications

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“…In vitro CZN metabolism is mediated by CYP2E1 in humans (Lucas et al, 1999), rats (Kobayashi et al, 2002), and cynomolgus monkeys (Amato et al, 1998), consistent with the single-site kinetics observed in these African green monkeys and further supporting the role of CYP2E1 as the sole enzyme importantly involved in CZN metabolism.…”

Section: Discussionmentioning

confidence: 58%

“…Chlorzoxazone (CZN), a clinically used muscle relaxant, is metabolized by CYP2E1 to 6-hydroxychlorzoxazone (6OHCZN), and this reaction has been established as a phenotypic measure of CYP2E1 activity in vivo in humans (Lucas et al, 1999) and in vitro in rats (Kobayashi et al, 2002) and cynomolgus monkeys (Amato et al, 1998). No studies linking in vivo CZN disposition, in vitro hepatic CZN metabolism, and hepatic CYP2E1 protein levels have been published in any species.…”

Section: Introductionmentioning

confidence: 99%

“…Many low molecular weight compounds such as benzene and carbon tetrachloride are also CYP2E1 substrates (Caro and Cederbaum, 2004). CYP2E1 produces a high level of reactive oxygen species, without need of a ligand, that can result in cell damage from lipid peroxidation and DNA strand breaks (Caro and Cederbaum, 2004).Chlorzoxazone (CZN), a clinically used muscle relaxant, is metabolized by CYP2E1 to 6-hydroxychlorzoxazone (6OHCZN), and this reaction has been established as a phenotypic measure of CYP2E1 activity in vivo in humans (Lucas et al, 1999) and in vitro in rats (Kobayashi et al, 2002) and cynomolgus monkeys (Amato et al, 1998). No studies linking in vivo CZN disposition, in vitro hepatic CZN metabolism, and hepatic CYP2E1 protein levels have been published in any species.…”

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confidence: 99%

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In Vivo and in Vitro Characterization of Chlorzoxazone Metabolism and Hepatic CYP2E1 Levels in African Green Monkeys: Induction by Chronic Nicotine Treatment

Lee¹,

Yue²,

Tyndale³

2006

Drug Metab Dispos

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ABSTRACT:CYP2E1 metabolizes compounds, including clinical drugs, organic solvents, and tobacco-specific carcinogens. Chlorzoxazone (CZN) is a probe drug used to phenotype for CYP2E1 activity. Smokers have increased CZN clearance during smoking compared with nonsmoking periods; however, it is unclear which cigarette smoke component is causing the increased activity. The relationships between in vivo CZN disposition, in vitro CZN metabolism, and hepatic CYP2E1 have not been investigated in a within-animal design. In control-treated monkeys (Cercopithecus aethiops), the in vivo CZN area under the curve extrapolated to infinity (AUC inf ) was 19.7 ؎ 4.5 g ؋ h/ml, t 1/2 was 0.57 ؎ 0.07 h, and terminal disposition rate constant calculated from last three to four points on the log-linear end of the concentration versus time curve was 1.2 ؎ 0.2 /h. In vitro, the apparent V max was 3.48 ؎ 0.02 pmol/ min/g microsomal protein, and the K m was 95.4 ؎ 1.8 M. CYP2E1 is a drug-metabolizing enzyme that biotransforms many compounds, including clinical drugs such as acetaminophen and halothane (Caro and Cederbaum, 2004). CYP2E1 also metabolizes ethanol (Lieber, 1999) and can be induced by ethanol in rats (Howard et al., 2001), rabbits (Lieber, 1999), and humans (Oneta et al., 2002). CYP2E1 contributes to ethanol metabolism at high blood alcohol concentrations in humans (Salaspuro and Lieber, 1978) and rats (Matsumoto et al., 1996). Many low molecular weight compounds such as benzene and carbon tetrachloride are also CYP2E1 substrates (Caro and Cederbaum, 2004). CYP2E1 produces a high level of reactive oxygen species, without need of a ligand, that can result in cell damage from lipid peroxidation and DNA strand breaks (Caro and Cederbaum, 2004).Chlorzoxazone (CZN), a clinically used muscle relaxant, is metabolized by CYP2E1 to 6-hydroxychlorzoxazone (6OHCZN), and this reaction has been established as a phenotypic measure of CYP2E1 activity in vivo in humans (Lucas et al., 1999) and in vitro in rats (Kobayashi et al., 2002) and cynomolgus monkeys (Amato et al., 1998). No studies linking in vivo CZN disposition, in vitro hepatic CZN metabolism, and hepatic CYP2E1 protein levels have been published in any species. The in vivo CZN disposition, in vitro CZN metabolism, and hepatic CYP2E1 protein levels have not yet been investigated in African green monkeys (vervets, Cercopithecus aethiops). This monkey is a useful model of human metabolism; it has been established as a model of CYP2A6 (Schoedel et al., 2003) and CYP2B6 (Lee et al., 2006) isozyme metabolism. Our model provides an opportunity to investigate the relationship between these three variables in a nonhuman primate. African green monkey CYP2E1 has not yet been sequenced, but it is expected to have similar amino acid homology to that of human CYP2E1. Other monkeys such as the cynomolgus monkey (Macaca fascicularis) and the rhesus monkey (Macaca mulatta) have 92 and 95% amino acid homology to human Conflict of Interest Statement: R.F.T. is a shareholder in Nicogen, a company fo...

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Section: Discussionmentioning

confidence: 58%

Section: Introductionmentioning

confidence: 99%

mentioning

confidence: 99%

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In Vivo and in Vitro Characterization of Chlorzoxazone Metabolism and Hepatic CYP2E1 Levels in African Green Monkeys: Induction by Chronic Nicotine Treatment

Lee¹,

Yue²,

Tyndale³

2006

Drug Metab Dispos

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“…However, had such an interaction occurred, it could not have been observed using the study design adopted. The speci®city of chlorzoxazone as a probe for CYP2E1 has also been the subject of some discussion, although current consensus appears to judge it as suf®ciently speci®c to be useful [13].…”

Section: Discussionmentioning

confidence: 99%

An interaction between the cytochrome P450 probe substrates chlorzoxazone (CYP2E1) and midazolam (CYP3A)

Palmer

Scott

Gibson³

et al. 2001

Brit J Clinical Pharma

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Aims The use of multiple probe substrates to evaluate the activity of drug metabolizing enzymes requires that there are no inter±substrate interactions. As part of a series of studies to develop a clinically useful collection of probe substrates that could be given alone or in any combination, we observed an interaction between midazolam (MDZ) and another component of the six-drug cocktail. Published data indicated that the interacting component was likely to be chlorzoxazone. This was investigated as part of a second study. The data relating to the interaction from both studies are reported here. Methods Both studies were performed in 16 healthy subjects. All treatments were given orally after an overnight fast. In study 1, which was performed to a four-period, open, crossover design, subjects received on separate occasions MDZ 5 mg, diclofenac 25 mg, a four drug cocktail (caffeine 100 mg, mephenytoin 100 mg, debrisoquine 10 mg and chlorzoxazone 250 mg) and a six drug cocktail (caffeine 100 mg, mephenytoin 100 mg, debrisoquine 10 mg, chlorzoxazone 250 mg, diclofenac 25 mg and MDZ 5 mg). In study 2, which was performed to a two-period, open, crossover design, subjects received a ®ve drug cocktail (as the six drug cocktail in the ®rst study, but without chlorzoxazone and with diclofenac dose increased to 50 mg) and a six drug cocktail (as ®ve drug cocktail, with chlorzoxazone 250 mg). In both studies, blood samples were taken for measurement of plasma MDZ and 1-hydroxy MDZ (1-OH MDZ) concentrations. In study 1, blood samples were taken up to 12 h post-dose while in study 2 a single sample was taken 2 h after dosing. In study 1, the potential interaction between MDZ and the other components of the six drug cocktail was assessed by comparing AUC last ratios (1-OH MDZ/MDZ) between the two treatments. Additionally, a single sampling timepoint of 2 h post-dose for determination of concentration, rather than AUC, ratios was established. The 2 h plasma concentration ratios from studies 1 and 2 were combined and a pooled analysis performed to compare ratios within each study (to determine the change in ratio when MDZ was dosed with and without chlorzoxazone) and between studies (to determine the consistency of the ratios when MDZ was given either as part of the two six drug cocktails or when given alone and as part of the ®ve drug cocktail). Results In study 1, both the AUC last ratio and the 2 h post-dose plasma concentration ratio were reduced when MDZ was given as part of the six drug cocktail in comparison with those for MDZ alone. This was the result of an increase in MDZ, rather than decrease in 1-OH MDZ, concentrations and was considered to result from a reduction in ®rst pass metabolism of MDZ. The geometric mean AUC last values (with 95% CI) for MDZ were 95.6 (79.0, 115.7) and 160.4 (133.6, 192.6) mg l x1 h when given alone and as part of the six drug cocktail, respectively. The corresponding values for 1-OH MDZ were 789.6 (697.6, 893.6) and 791.4 (701.7, 892.6) mg l x1 h. The ratio of adjusted geometric mean ...

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“…Low protein intake, as in Madras and Soweto, impairs CYP induction: thus, the rate of theophylline clearance in Madras controls was lower than in Manchester controls, but significantly increased in local non-alcoholic patients (44), alongside regular close exposure to kerosene fumes and little ascorbic acid (36,103). At the time of the studies at Soweto, it was not known that chlorzoxazone is a probe of CYP2E1 induction, as by ethanol (92): in these patients, with predominantly alcoholic disease, theophylline clearance was similar to that in healthy controls, but the impact of RXS evident from a fall in plasma GSH, increased oxidation of plasma ascorbic acid, decreased urinary inorganic sulphate and increased D-glucaric acid (138). A subnormal concentration of zinc in serum (5,138) and erythrocytes (62,116) correlates with reduced exocrine secretory capacity (62), rather than poor intake, and has no bearing on CYP function.…”

Section: Towards Treatment Clues For a Prescriptionmentioning

confidence: 99%

Micronutrient ('Antioxidant') Therapy for Chronic Pancreatitis: Basis and Clinical Experience

Braganza

The Pancreapedia: Exocrine Pancreas Knowledge Base

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Chlorzoxazone, a selective probe for phenotyping CYP2E1 in humans

Cited by 100 publications

References 0 publications

In Vivo and in Vitro Characterization of Chlorzoxazone Metabolism and Hepatic CYP2E1 Levels in African Green Monkeys: Induction by Chronic Nicotine Treatment

In Vivo and in Vitro Characterization of Chlorzoxazone Metabolism and Hepatic CYP2E1 Levels in African Green Monkeys: Induction by Chronic Nicotine Treatment

An interaction between the cytochrome P450 probe substrates chlorzoxazone (CYP2E1) and midazolam (CYP3A)

Micronutrient ('Antioxidant') Therapy for Chronic Pancreatitis: Basis and Clinical Experience

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