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Chiba K, Shimizu K, Kato M, Miyazaki T, Nishibayashi T, Terada K, Sugiyama Y. Estimation of Interindividual Variability of Pharmacokinetics of CYP2C9 Substrates in Humans. J Pharm Sci 2017; 106:2695-2703. [DOI: 10.1016/j.xphs.2017.04.021] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/07/2017] [Revised: 04/05/2017] [Accepted: 04/10/2017] [Indexed: 01/10/2023]
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Genetic markers in the EET metabolic pathway are associated with outcomes in patients with aneurysmal subarachnoid hemorrhage. J Cereb Blood Flow Metab 2015; 35:267-76. [PMID: 25388680 PMCID: PMC4426743 DOI: 10.1038/jcbfm.2014.195] [Citation(s) in RCA: 18] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 06/10/2014] [Revised: 10/10/2014] [Accepted: 10/14/2014] [Indexed: 12/25/2022]
Abstract
Preclinical studies show that epoxyeicosatrienoic acids (EETs) regulate cerebrovascular tone and protect against cerebral ischemia. We investigated the relationship between polymorphic genes involved in EET biosynthesis/metabolism, cytochrome P450 (CYP) eicosanoid levels, and outcomes in 363 patients with aneurysmal subarachnoid hemorrhage (aSAH). Epoxyeicosatrienoic acids and dihydroxyeicosatetraenoic acid (DHET) cerebrospinal fluid (CSF) levels, as well as acute outcomes defined by delayed cerebral ischemia (DCI) or clinical neurologic deterioration (CND), were assessed over 14 days. Long-term outcomes were defined by Modified Rankin Scale (MRS) at 3 and 12 months. CYP2C8*4 allele carriers had 44% and 36% lower mean EET and DHET CSF levels (P=0.003 and P=0.007) and were 2.2- and 2.5-fold more likely to develop DCI and CND (P=0.039 and P=0.041), respectively. EPHX2 55Arg, CYP2J2*7, CYP2C8*1B, and CYP2C8 g.36785A allele carriers had lower EET and DHET CSF levels. CYP2C8 g.25369T and CYP2C8 g.36755A allele carriers had higher EET levels. Patients with CYP2C8*2C and EPHX2 404del variants had worse long-term outcomes while those with EPHX2 287Gln, CYP2J2*7, and CYP2C9 g.816G variants had favorable outcomes. Epoxyeicosatrienoic acid levels were associated with Fisher grade and unfavorable 3-month outcomes. Dihydroxyeicosatetraenoic acids were not associated with outcomes. No associations passed Bonferroni multiple testing correction. These are the first clinical data demonstrating the association between the EET biosynthesis/metabolic pathway and the pathophysiology of aSAH.
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Abstract
Since the introduction in the 1950s, warfarin has become the commonly used oral anticoagulant for the prevention of thromboembolism in patients with deep vein thrombosis, atrial fibrillation or prosthetic heart valve replacement. Warfarin is highly efficacious; however, achieving the desired anticoagulation is difficult because of its narrow therapeutic window and highly variable dose response among individuals. Bleeding is often associated with overdose of warfarin. There is overwhelming evidence that an individual's warfarin maintenance is associated with clinical factors and genetic variations, most notably polymorphisms in cytochrome P450 2C9 and vitamin K epoxide reductase subunit 1. Numerous dose-prediction algorithms incorporating both genetic and clinical factors have been developed and tested clinically. However, results from major clinical trials are not available yet. This review aims to provide an overview of the field of warfarin which includes information about the drug, genetics of warfarin dose requirements, dosing algorithms developed and the challenges for the clinical implementation of warfarin pharmacogenetics.
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Flora DR, Tracy TS. Development of an in vitro system with human liver microsomes for phenotyping of CYP2C9 genetic polymorphisms with a mechanism-based inactivator. Drug Metab Dispos 2011; 40:836-42. [PMID: 22205778 DOI: 10.1124/dmd.111.043372] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/13/2022] Open
Abstract
Polymorphisms in cytochrome P450 enzymes can significantly alter the rate of drug metabolism, as well as the extent of drug-drug interactions. Individuals who homozygotically express the CYP2C9*3 allele (I359L) of CYP2C9 exhibit ∼70 to 80% reductions in the oral clearance of drugs metabolized through this pathway; the reduction in clearance is ∼40 to 50% for heterozygotic individuals. Although these polymorphisms result in a decrease in the activity of individual enzyme molecules, we hypothesized that decreasing the total number of active enzyme molecules in an in vitro system (CYP2C9*1/*1 human liver microsomes) by an equivalent percentage could produce the same net change in overall metabolic capacity. To this end, the selective CYP2C9 mechanism-based inactivator tienilic acid was used to reduce irreversibly the total CYP2C9 activity in human liver microsomes. Tienilic acid concentrations were effectively titrated to produce microsomal preparations with 43 and 73% less activity, mimicking the CYP2C9*1/*3 and CYP2C9*3/*3 genotypes, respectively. With probe substrates specific for other major cytochrome P450 enzymes (CYP1A2, CYP2B6, CYP2C8, CYP2C19, CYP2D6, CYP2E1, and CYP3A4), no apparent changes in the rate of metabolism were noted for these enzymes after the addition of tienilic acid, which suggests that this model is selective for CYP2C9. In lieu of using rare human liver microsomes from CYP2C9*1/*3 and CYP2C9*3/*3 individuals, a tienilic acid-created knockdown in human liver microsomes may be an appropriate in vitro model to determine CYP2C9-mediated metabolism of a given substrate, to determine whether other drug-metabolizing enzymes may compensate for reduced CYP2C9 activity, and to predict the extent of genotype-dependent drug-drug interactions.
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Affiliation(s)
- Darcy R Flora
- Department of Experimental and Clinical Pharmacology, College of Pharmacy, University of Minnesota, Minneapolis, Minnesota, USA
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Arun Kumar AS, Chakradhara Rao US, Umamaheswaran G, Ramu P, Kesavan R, Shewade DG, Balachandar J, Adithan C. Haplotype Structures of Common Variants of CYP2C8, CYP2C9, and ADRB1 Genes in a South Indian Population. Genet Test Mol Biomarkers 2011; 15:407-13. [DOI: 10.1089/gtmb.2010.0170] [Citation(s) in RCA: 10] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/12/2022] Open
Affiliation(s)
- Annan Sudarsan Arun Kumar
- Pharmacogenomics Laboratory, Department of Pharmacology, Jawaharlal Institute of Postgraduate Medical Education and Research, Pondicherry, India
| | | | - Gurusamy Umamaheswaran
- Pharmacogenomics Laboratory, Department of Pharmacology, Jawaharlal Institute of Postgraduate Medical Education and Research, Pondicherry, India
| | - Periyasamy Ramu
- Pharmacogenomics Laboratory, Department of Pharmacology, Jawaharlal Institute of Postgraduate Medical Education and Research, Pondicherry, India
| | - Ramasamy Kesavan
- Pharmacogenomics Laboratory, Department of Pharmacology, Jawaharlal Institute of Postgraduate Medical Education and Research, Pondicherry, India
| | - Deepak Gopal Shewade
- Pharmacogenomics Laboratory, Department of Pharmacology, Jawaharlal Institute of Postgraduate Medical Education and Research, Pondicherry, India
| | - Jayaraman Balachandar
- Department of Cardiology, Jawaharlal Institute of Postgraduate Medical Education and Research, Pondicherry, India
| | - Chandrasekaran Adithan
- Pharmacogenomics Laboratory, Department of Pharmacology, Jawaharlal Institute of Postgraduate Medical Education and Research, Pondicherry, India
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Piatkov I, Rochester C, Jones T, Boyages S. Warfarin toxicity and individual variability-clinical case. Toxins (Basel) 2010; 2:2584-92. [PMID: 22069565 PMCID: PMC3153177 DOI: 10.3390/toxins2112584] [Citation(s) in RCA: 17] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/19/2010] [Revised: 10/21/2010] [Accepted: 10/27/2010] [Indexed: 11/16/2022] Open
Abstract
Warfarin is a widely used anticoagulant in the treatment and prevention of thrombosis, in the treatment for chronic atrial fibrillation, mechanical valves, pulmonary embolism, and dilated cardiomyopathy. It is tasteless and colorless, was used as a poison, and is still marketed as a pesticide against rats and mice. Several long-acting warfarin derivatives-superwarfarin anticoagulants-such as brodifacoum, diphenadione, chlorophacinone, bromadiolone, are used as pesticides and can produce profound and prolonged anticoagulation. Several factors increase the risk of warfarin toxicity. However, polymorphisms in cytochrome P450 genes and drug interactions account for most of the risk for toxicity complications. Each person is unique in their degree of susceptibility to toxic agents. The toxicity interpretation and the health risk of most toxic substances are a subject of uncertainty. Genetically determined low metabolic capacity in an individual can dramatically alter the toxin and metabolite levels from those normally expected, which is crucial for drugs with a narrow therapeutic index, like warfarin. Personalized approaches in interpretation have the potential to remove some of the scientific uncertainties in toxicity cases.
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Affiliation(s)
- Irina Piatkov
- Diversity Health Institute, DHI Laboratory, ICPMR level 2, Sydney-West Area Health Service, Westmead Hospital, Westmead, NSW 2145, Australia.
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Muszkat M, Bialer O, Blotnick S, Adar L, Xie HG, Ufer M, Cascorbi I, Caraco Y. Effects of folic acid supplementation on the pharmacokinetics and anticoagulant effect of warfarin: an open-label, prospective study of long-term administration in adults. Clin Ther 2010; 32:347-56. [PMID: 20206792 DOI: 10.1016/j.clinthera.2010.02.008] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Accepted: 11/23/2009] [Indexed: 02/06/2023]
Abstract
BACKGROUND Folic acid supplementation in patients with folic acid deficiency has been associated with increased clearance of phenytoin to its cytochrome P450 (CYP) 2C9-mediated metabolite, 5-(4'-hydroxyphenyl)-5-phenylhydantoin. OBJECTIVE The aim of this study was to determine whether folic acid supplementation increases the dosage requirement of the CYP2C9 substrate warfarin, and the formation clearance of the CYP2C9-mediated product, (S)-7-hydroxywarfarin. METHODS Patients aged >or=18 years with folic acid deficiency who were receiving long-term treatment with a stable dosage of warfarin were studied prospectively, before and 30 to 60 days after the initiation of supplementation with folic acid. Warfarin dosage and international normalized ratio (INR) were documented, and the formation clearance of (S)- and (R)-7-hydroxywarfarin and the oral clearance of (S)- and (R)-warfarin were determined. RESULTS Twenty-four white patients (14 males; mean (SD) age, 55.0 [19.7] years; body mass index, 30.64 [6.8] kg/m(2)) were enrolled. Treatment with folic acid was associated with a significantly increased mean (SD) formation clearance of (S)-7-hydroxywarfarin (1.096 [0.816] vs 1.608 [1.302] mL/min; P = 0.048). Before folic acid supplementation, the mean (SD) warfarin dosage was 5.98 (2.12) mg/d, and the INR was 2.51 (0.55). During supplementation, the warfarin dosage was 6.17 (2.31) mg/d and the INR was 2.63 (0.65) (both, P = NS vs before supplementation). CONCLUSIONS Folic acid supplementation was associated with significantly increased formation clearance of (S)-7-hydroxywarfarin. Changes in warfarin dosage requirements and INR were nonsignificant.
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Affiliation(s)
- Mordechai Muszkat
- Division of Medicine, Hadassah-Hebrew University Medical Center, Jerusalem, Israel
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Chaudhry AS, Urban TJ, Lamba JK, Birnbaum AK, Remmel RP, Subramanian M, Strom S, You JH, Kasperaviciute D, Catarino CB, Radtke RA, Sisodiya SM, Goldstein DB, Schuetz EG. CYP2C9*1B promoter polymorphisms, in linkage with CYP2C19*2, affect phenytoin autoinduction of clearance and maintenance dose. J Pharmacol Exp Ther 2009; 332:599-611. [PMID: 19855097 DOI: 10.1124/jpet.109.161026] [Citation(s) in RCA: 44] [Impact Index Per Article: 2.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022] Open
Abstract
The commonly prescribed antiepileptic drug phenytoin has a narrow therapeutic range and wide interindividual variability in clearance explained in part by CYP2C9 and CYP2C19 coding variants. After finding a paradoxically low urinary phenytoin metabolite (S)/(R) ratio in subjects receiving phenytoin maintenance therapy with a CYP2C9*1/*1 and CYP2C19*1/*2 genotype, we hypothesized that CYP2C9 regulatory polymorphisms (rPMs), G-3089A and -2663delTG, in linkage disequilibrium with CYP2C19*2 were responsible. These rPMs explained as much as 10% of the variation in phenytoin maintenance dose in epileptic patients, but were not correlated with other patients' warfarin dose requirements or with phenytoin metabolite ratio in human liver microsomes. We hypothesized the rPMs affected CYP2C9 induction by phenytoin, a pregnane X receptor (PXR), and constitutive androstane receptor (CAR) activator. Transfection studies showed that CYP2C9 reporters with wild-type versus variant alleles had similar basal activity but significantly greater phenytoin induction by cotransfected PXR, CAR, and Nrf2 and less Yin Yang 1 transcription factor repression. Phenytoin induction of CYP2C9 was greater in human hepatocytes with the CYP2C9 wild type versus variant haplotype. Therefore, CYP2C9 rPMs affect phenytoin-dependent induction of CYP2C9 and phenytoin metabolism in humans, with an effect size comparable with that for CYP2C9*2 and 2C9*3. These findings may also be relevant to the clinical use of other PXR, CAR, and Nrf2 activators.
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Affiliation(s)
- Amarjit S Chaudhry
- Department of Pharmaceutical Sciences, St. Jude Children's Research Hospital, Memphis, TN 38105, USA
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Ghadam P, Sharifian R, Farsangi ZJ, Kianmehr Z, Lak M. CYP2C9 gene analysis of some Iranian hypersensitive patients to warfarin. Pak J Biol Sci 2009; 12:1160-1163. [PMID: 19899329 DOI: 10.3923/pjbs.2009.1160.1163] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 05/28/2023]
Abstract
For the first time in this study, the pharmacogenetic effects of CYP2C9 polymorphism on warfarin sensitivity in some Iranian patients who are on warfarin treatment were shown. The study group consisted of clinically sensitive patients (21 patients) and the control group (37 adult patients). For detection of CYP2C9*2 and CYP2C9*3 variants, a protocol based on restriction fragment length polymorphism based polymerase chain reaction with Eco47I and KpnI was used. In clinically sensitive patients about 81% and in normal response patients about 24.3% carried variant genotypes.
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Affiliation(s)
- P Ghadam
- Department of Biology, Faculty of Basic Sciences, Alzahra University, Tehran, Iran
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Prediction of the Effects of Genetic Polymorphism on the Pharmacokinetics of CYP2C9 Substrates from In Vitro Data. Pharm Res 2008; 26:822-35. [DOI: 10.1007/s11095-008-9781-2] [Citation(s) in RCA: 35] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/02/2008] [Accepted: 11/04/2008] [Indexed: 11/25/2022]
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Chialda L, Griffith LS, Heinig A, Pahl A. Prospective use of CYP pharmacogenetics and medication analysis to facilitate improved therapy - a pilot study. Per Med 2008; 5:37-45. [PMID: 29783392 DOI: 10.2217/17410541.5.1.37] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022]
Abstract
OBJECTIVES To assess the efficacy of cytochrome P450 (CYP) pharmacogenetic testing and medication interaction analysis in a controlled environment for reduction of events, stays in hospital, extra care and required extra doctors visits to the patients. METHODS A prospective cohort study of 28 patients in a geriatric care facility with multimedication and at least one report of an event was performed over a period of 7 months. In the first phase of the study the patients were closely monitored twice a day by the care staff, recording all potential events, regardless of association with the indication or not, requirement for extra care, requirement for an unplanned site visit from a physician and days in hospital. In a 1-month period, the patients were genotyped for the cytochromes CYP2C9, CYP2C19 and CYP2D6, and their medication analyzed for interactions, using a proprietary computer program. Recommendations for medication change based upon genetics and/or medication interaction analysis were made to the care physicians. In a second 3-month phase the patients were monitored as in Phase I. The data comparing Phase I with Phase II was analyzed using two way ANOVA. RESULTS Of the 28 patients in the study in both phases, 16 (55%) had genetic and/or medication interaction problems that required change of medication. A total of 11 out of 16 (69%) of the patients did have their medication altered by the care physician. Of the 11 patients, five (45%) demonstrated some betterment in the number of reported events after alteration of their medication. Of these five patients, three had improvements when their medication was altered for their genetics. A further three (one patient had improvements due to both effects) had improvements when their medication was altered after a medication interaction analysis. CONCLUSION Although an exploratory pilot study, this cohort study shows the possibilities and potential of pharmacogenetic testing for CYP alterations combined with medication interaction analysis of patients in a geriatric care facility.
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Affiliation(s)
- Ligia Chialda
- University of Erlangen-Nürnberg, Department of Experimental Pharmacology, Fahrstrasse 17, D-91054 Erlangen, Germany.
| | - Lee S Griffith
- Awenydd Gene Diagnostic, Engesserstrasse 4b, 79108 Freiburg, Germany.
| | - Antoinette Heinig
- Evangelical Hospital Düsseldorf, Kirchfeldstrasse 40, Düsseldorf, Germany
| | - Andreas Pahl
- University of Erlangen-Nürnberg, Department of Experimental Pharmacology, Fahrstrasse 17, D-91054 Erlangen, Germany.
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Muszkat M, Blotnik S, Elami A, Krasilnikov I, Caraco Y. Warfarin metabolism and anticoagulant effect: a prospective, observational study of the impact of CYP2C9 genetic polymorphism in the presence of drug-disease and drug-drug interactions. Clin Ther 2007; 29:427-37. [PMID: 17577464 DOI: 10.1016/s0149-2918(07)80081-6] [Citation(s) in RCA: 35] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Accepted: 01/22/2007] [Indexed: 11/20/2022]
Abstract
BACKGROUND Cytocbrome P450 (CYP) 2C9 polymorphism affects the warfarin dosage requirement in stable outpatients. However, it is not known whether the CYP2C9 genotype contributes to the variability in warfarin dosage in the presence of drug-disease and drug-drug interactions. OBJECTIVE The aim of this study was to examine the effects of CYP2C9 genetic polymorphism on warfarin dosage requirements in patients with severe comorbid conditions and those treated with medications that potentially interact with warfarin. METHODS This prospective, observational study was conducted at Hadassah University Hospital, Jerusalem, Israel. Data from consecutive patients treated with warfarin for at least 3 months and admitted to the internal medicine ward were eligible for inclusion. Clinical data, international normalized ratio (INR), and warfarin dosage were recorded from medical records. The CYP2C9 genotype was determined using polymerase chain reaction restriction fragment length polymorphism, and plasma concentrations of (S)- and (R)-warfarin were determined by high-performance liquid chromatography using chiral methods. RESULTS One hundred nineteen subjects (52% women) were studied. Mean age was 65.8 years (95% CI, 63.1-68.4), and weight was 74.9 kg (95% CI, 72.1-77.7). The mean warfarin dosage was 33% lower in patients with the CYP2C9-*1/*3 genotype (mean [SEM], 0.045 [0.006] mg/kg x d(-1)) compared with the CYP2C9-*1/*1 genotype (0.067 [0.004] mg/kg x d(-1)) (P=0.008); an intermediate value was found for the CYP2C9-*1/*2 genotype (0.062 [0.008] mg/kg x d(-1)). However, despite the lower dosage, INR was significantly higher in patients with the *1/*3 genotype (mean [95% CI], 3.29 [2.44-4.14]) (n=18) compared with the *1/*1 genotype (2.52 [2.34-2.71]) (n=64) (P=0.029). In addition to genotype, older age, congestive heart failure (CHF), and treatment with antibiotics were associated with lower warfarin dosages, whereas treatment with drug-metabolism inducers was associated with higher warfarin dosages. In addition, the ratios of (S)- to (R)-warfarin concentrations were significantly higher in patients with *1/*3 compared with those in patients with the *1/*1 genotype. CONCLUSIONS In this study population of patients with severe comorbid conditions and those treated with medications that potentially interact with warfarin, CYP2C9 *1/*3 genotype, older age, CHF, and the use of antibiotics were associated with lower warfarin dosage requirements. The CYP2C9*1/*3 genotype, compared with CYP2C9 *1/*1, was associated with 33% lower mean warfarin dosage requirements and higher INR values, which were higher than the upper therapeutic range of INR (ie, 3). Genetic CYP2C9 polymorphism contributed to the variability in warfarin dosage requirements in the presence of drug-disease and drug-drug interactions.
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Affiliation(s)
- Mordechai Muszkat
- Division o f Medicine, Hadassah University Hospital, Jerusalem, Israel
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Lee SY, Nam MH, Kim JS, Kim JW. A case report of a patient carrying CYP2C9*3/4 genotype with extremely low warfarin dose requirement. J Korean Med Sci 2007; 22:557-9. [PMID: 17596671 PMCID: PMC2693655 DOI: 10.3346/jkms.2007.22.3.557] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 11/20/2022] Open
Abstract
We report a case of intolerance to warfarin dosing due to impaired drug metabolism in a patient with CYP2C9*3/*4. A 73-yr-old woman with atrial fibrilation was taking warfarin. She attained a high prothrombin time international normalized ratio (INR) at the standard doses during the induction of anticoagulation and extremely low dose of warfarin (6.5 mg/week) was finally chosen to reach the target INR. Genotyping for CYP2C9 revealed that this patient had a genotype CYP2C9*3/*4. This is the first Korean compound heterozygote for CYP2C9*3 and *4. This case suggests the clinical usefulness of pharmacogenetic testing for individualized dosage adjustments of warfarin.
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Affiliation(s)
- Soo-Youn Lee
- Department of Laboratory Medicine, Samsung Medical Center, Sungkyunkwan University School of Medicine, Seoul, Korea
| | - Myung-Hyun Nam
- Department of Laboratory Medicine, Samsung Medical Center, Sungkyunkwan University School of Medicine, Seoul, Korea
| | - June Soo Kim
- Department of Internal Medicine, Samsung Medical Center, Sungkyunkwan University School of Medicine, Seoul, Korea
| | - Jong-Won Kim
- Department of Laboratory Medicine, Samsung Medical Center, Sungkyunkwan University School of Medicine, Seoul, Korea
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Elliot DJ, Suharjono, Lewis BC, Gillam EMJ, Birkett DJ, Gross AS, Miners JO. Identification of the human cytochromes P450 catalysing the rate-limiting pathways of gliclazide elimination. Br J Clin Pharmacol 2007; 64:450-7. [PMID: 17517049 DOI: 10.1111/j.1365-2125.2007.02943.x] [Citation(s) in RCA: 38] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/01/2023] Open
Abstract
AIMS To identify the human cytochrome P450 (CYP) enzymes responsible for the formation of the 6beta-hydroxy (6beta-OHGz), 7beta-hydroxy (7beta-OHGz) and hydroxymethyl (MeOH-Gz) metabolites of gliclizide (Gz). METHODS 6beta-OHGz, 7beta-OHGz and MeOH-Gz formation by human liver microsomes and a panel of recombinant human P450s was measured using a high-performance liquid chromatography procedure, and the kinetics of metabolite formation was determined for each pathway. Effects of prototypic CYP enzyme selective inhibitors were characterized for each of the microsomal metabolic pathways. RESULTS Microsomes from six human livers converted Gz to its 6beta-OHGz, 7beta-OHGz, and MeOH-Gz metabolites, with respective mean (+/- SD) K(m) values of 461 +/- 139, 404 +/- 143 and 334 +/- 75 microm and mean V(max) values of 130 +/- 55, 82 +/- 31 and 268 +/- 115 pmol min(-1) mg(-1), respectively. V(max)/K(m) ratios for the microsomal reactions parallelled relative metabolite formation in vivo. Sulfaphenazole inhibited microsomal 6beta-OHGz, 7beta-OHGz and MeOH-Gz formation by 87, 83 and 64%, respectively, whereas S-mephenytoin caused significant inhibition (48%) of only MeOH-Gz formation. Recombinant CYP2C9, CYP2C18 and CYP2C19 catalysed all hydroxylation pathways, whereas CYP2C8 formed only 6beta-OHGz and 7beta-OHGz. CONCLUSION Taken together, the results indicate that CYP2C9 is the major contributor to Gz metabolic clearance, although CYP2C19 may also be involved in MeOH-Gz formation (the major metabolic pathway). Factors known to influence CYP2C9 activity will provide the main source of variability in Gz pharmacokinetics.
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Affiliation(s)
- David J Elliot
- Department of Clinical Pharmacology, Flinders University and Flinders Medical Centre, Bedford Park, Adelaide, Australia
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Argikar UA, Cloyd JC, Birnbaum AK, Leppik IE, Conway J, Kshirsagar S, Oetting WS, Klein EC, Remmel RP. Paradoxical urinary phenytoin metabolite (S)/(R) ratios in CYP2C19*1/*2 patients. Epilepsy Res 2006; 71:54-63. [PMID: 16815679 DOI: 10.1016/j.eplepsyres.2006.05.015] [Citation(s) in RCA: 17] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/14/2006] [Accepted: 05/22/2006] [Indexed: 11/18/2022]
Abstract
Phenytoin (PHT) is primarily metabolized to 5-(4'-hydroxyphenyl)-5-phenylhydantoin (p-HPPH), accounting for 67-88% of an administered dose in humans. p-HPPH is formed by the cytochrome (CYP) 450 enzymes CYP2C9 and CYP2C19, then glucuronidated and excreted into the urine. CYP2C9 catalyses the prochiral formation of (R) and (S)-p-HPPH, and is approximately 40 times more stereoselective towards the formation of the (S) isomer whereas CYP2C19 is not stereoselective. Because of differential stereoselectivity, polymorphisms in the genes can alter the (S)/(R)-p-HPPH ratios. Genotyping for CYP2C9 and CYP2C19 was accomplished by a Taqman based assay. Twelve and twenty-four hour urine samples were collected from 45 epilepsy patients taking PHT under steady-state conditions and (S)/(R) ratios of p-HPPH were determined by chiral HPLC separation. The mean urinary (S)/(R) ratio in the 12-24h urine collection in subjects homozygous for CYP2C9*1/*1, CYP2C19*1/*1 was 24.2+/-3.1(n=21), whereas ratios in CYP2C9*1/*2 and CYP2C9*1/*3 subjects, were 11.1+/-3.3(n=7) and 2.7+/-0.6(n=2), respectively. One CYP2C9*2/*3 patient had a ratio of 2.1. Unexpectedly, CYP2C9*1/*1, CYP2C19*1/*2 subjects had a mean (S)/(R) ratio as low as 12.9+/-1.7(n=12). Our results are generally consistent with single dose PHT studies. However, the (S)/(R)-p-HPPH ratios for the CYP2C9*1/*1, CYP2C19*1/*2 subjects, expected to be in the range of 30-40, were only 12.9, suggesting some undetected linkage disequilibrium between CYP2C9 and CYP2C19 genes that could affect PHT elimination. Furthermore, our study suggests that measurement of urine ratios cannot be used as a marker for genotype determination.
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Affiliation(s)
- Upendra A Argikar
- Department of Medicinal Chemistry, College of Pharmacy, University of Minnesota, Minneapolis, MN 55414, USA
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Gibbs JP, Hyland R, Youdim K. Minimizing Polymorphic Metabolism in Drug Discovery: Evaluation of the Utility of in Vitro Methods for Predicting Pharmacokinetic Consequences Associated with CYP2D6 Metabolism. Drug Metab Dispos 2006; 34:1516-22. [PMID: 16763018 DOI: 10.1124/dmd.105.008714] [Citation(s) in RCA: 31] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/16/2022] Open
Abstract
Minimizing interindividual variability in drug exposure is an important goal for drug discovery. The reliability of the selective CYP2D6 inhibitor quinidine was evaluated in a retrospective analysis using a standardized approach that avoids laboratory-to-laboratory variation. The goal was to evaluate the reliability of in vitro metabolism studies for predicting extensive metabolizer (EM)/poor metabolizer (PM) exposure differences. Using available literature, 18 CYP2D6 substrates were selected for further analysis. In vitro microsomal studies were conducted at 1 microM substrate and 0.5 microM P450 to monitor substrate depletion. An estimate of the fraction metabolized by CYP2D6 in microsomes was derived from the rate constant determined with and without 1 microM quinidine for 11 substrates. Clearance in EM and PM subjects and fractional recovery of metabolites were taken from the literature. A nonlinear relationship between the contribution of CYP2D6 and decreased oral clearance for PMs relative to EMs was evident. For drugs having <60% CYP2D6 involvement in vivo, a modest difference between EM and PM exposure was observed (<2.5-fold). For major CYP2D6 substrates (>60%), more dramatic exposure differences were observed (3.5- to 53-fold). For compounds primarily eliminated by hepatic P450 and with sufficient turnover to be evaluated in vitro, the fraction metabolized by CYP2D6 in vitro compared favorably with the in vivo data. The in vitro estimation of fraction metabolized using quinidine as a specific inhibitor provided an excellent predictive tool. Results from microsomal substrate depletion experiments can be used with confidence to select compounds in drug discovery using a cutoff of >60% metabolism by CYP2D6.
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Affiliation(s)
- John P Gibbs
- Pharmacokinetics, Dynamics, and Metabolism, Pfizer Inc, Groton, CT 06340, USA.
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Lee SY, Kim JS, Kim JW. A case of intolerance to warfarin dosing in an intermediate metabolizer of CYP2C9. Yonsei Med J 2005; 46:843-6. [PMID: 16385662 PMCID: PMC2810600 DOI: 10.3349/ymj.2005.46.6.843] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 07/12/2004] [Accepted: 08/23/2004] [Indexed: 11/27/2022] Open
Abstract
We report a case of intolerance to warfarin dosing due to impaired drug metabolism in a patient heterozygous for the CYP2C9*3 allele. A 30-year-old woman with an artificial cardiac pacemaker was taking warfarin to prevent thromboembolism. This patient had an extremely elevated international normalized ratio (INR) of prothrombin time (PT) following standard doses of warfarin and experienced difficulties during the induction of anticoagulation. Genotyping for CYP2C9 revealed that this patient was an intermediate metabolizer with genotype CYP2C9*1/*3. This case suggests the clinical usefulness of pharmacogenetic testing for individualized dosage adjustments of warfarin.
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Affiliation(s)
- Soo-Youn Lee
- Department of Laboratory Medicine, Samsung Medical Center, Sungkyunkwan University School of Medicine, Seoul, Korea
| | - June Soo Kim
- Department of Internal Medicine, Samsung Medical Center, Sungkyunkwan University School of Medicine, Seoul, Korea
| | - Jong-Won Kim
- Department of Laboratory Medicine, Samsung Medical Center, Sungkyunkwan University School of Medicine, Seoul, Korea
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18
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Hong X, Zhang S, Mao G, Jiang S, Zhang Y, Yu Y, Tang G, Xing H, Xu X. CYP2C9*3 allelic variant is associated with metabolism of irbesartan in Chinese population. Eur J Clin Pharmacol 2005; 61:627-34. [PMID: 16094537 DOI: 10.1007/s00228-005-0976-8] [Citation(s) in RCA: 29] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/18/2005] [Accepted: 06/28/2005] [Indexed: 11/29/2022]
Abstract
OBJECTIVE There is considerable variability in the individual pharmaceutical dosages required to achieve optimal therapeutic effects, which may be due to environmental or genetic factors. The objective of this study was to test the presence of the CYP2C9*3 allelic variant in the Chinese population and to investigate the association of this variant with both metabolism and therapeutic efficacy of irbesartan on essential hypertension. METHODS In this study, we enrolled 711 subjects from Taihu County and 376 subjects from Dongzhi County in Anhui Province, China. All subjects received a single oral dose of 150 mg irbesartan daily for 28 days. The plasma concentration of irbesartan at 24 h after dosing on the 27th day and at 6 h after dosing on the 28th day was detected using fluorescence-high-performance liquid chromatography. CYP2C9 genotypes were determined using polymerase chain reaction-restriction fragment length polymorphism. RESULTS No CYP2C9*2 allele was found in 235 Chinese samples and was removed from further study. The mean frequency of the CYP2C9*3 allele was 3.65%, while no CYP2C9*3/*3 genotype was detected. Multiple linear regression analyses revealed that the CYP2C9*3 allele carriers had significantly higher irbesartan concentrations in plasma at 6 h (Taihu: P < 0.0001; Dongzhi: P = 0.03) and 24 h (Taihu: P < 0.0001; Dongzhi: P = 0.00013) after dosing. No significant association was found between the CYP2C9*3 allelic variant and the therapeutic effect of irbesartan on essential hypertension. CONCLUSION Our study suggests that the CYP2C9*3 plays an important role in the metabolism of irbesartan and/or is in linkage disequilibrium with another potential CYP2C9 allele, both of which possibly modify the pharmacokinetics of irbesartan.
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Affiliation(s)
- Xiumei Hong
- Life Science School, University of Science and Technology of China, Huangshan Road, Hefei City, Anhui Province, China
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19
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Topić E, Stefanović M, Samardzija M. Association between the CYP2C9 polymorphism and the drug metabolism phenotype. Clin Chem Lab Med 2004; 42:72-8. [PMID: 15061384 DOI: 10.1515/cclm.2004.014] [Citation(s) in RCA: 21] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/15/2022]
Abstract
CYP2C9, an isoform of the cytochrome P450 enzyme, is involved in the metabolism of most of the drugs of choice for the treatment of thromboembolic disorders. Functional polymorphism is associated with two variant alleles (alleles *2 and *3) encoding CYP2C9 enzymes with a potentially different catalytic activity. The aim of the study was to determine the frequency of the CYP2C9 polymorphism in a representative sample of the Croatian population (n = 177) and to assess the association between the CYP2C9 polymorphism and the warfarin dose in patients with thromboembolism (n = 181). The CYP2C9 genotype was determined by polymerase chain reaction-restriction fragment length poymorphism (PCR-RFLP). According to the CYP2C9 genotype distribution, 31.2% of the healthy subjects were identified with a heterozygous or homozygous CYP2C9 variant genotype. The frequency of 2C9*2 and 2C9*3 alleles was 12.4% and 3.7%, respectively. There was no gender-related genotype or allele difference. In thromboembolism patients, the frequency of CYP2C9 alleles *2 and *3 was 17.4% and 6.6%, respectively, and did not differ significantly from the control group. Almost half (42.5%) of the patients carried at least one variant CYP2C9 genotype. The allele difference between patient subgroups receiving warfarin doses lower and higher than the optimal warfarin dose (4.1 mg/day) was significant (p = 0.027), especially for allele 2C9*3 (p = 0.019; OR 3.250, 95%, CI 1.263-8.413). Comparison of the warfarin dose between patients with different genotypes yielded a significant dose difference between the patients with wild-type genotype and those with variant genotypes (Kruskall-Wallis, chi2 = 9.745, p = 0.008). The results of the association of each of five genotype combinations with the warfarin maintenance dose revealed it to be significantly related to the genotype (Kruskall-Wallis, chi2 = 12.854, p = 0.025). Expressed as percentage of the mean dose in patients with wild-type alleles, the mean warfarin maintenance dose was 92% in 2C9*2 heterozygotes, 74% in 2C*3 heterozygotes, 61% in 2C9*2 homozygotes, 34% in 2C9*3 homozygotes and 63% in compound heterozygotes for 2C9*2 and 2C9*3. Although the mean maintenance dose in homozygous *2/*2 and compound *2/*3 genotype patients was markedly lower (mean 2.66 mg and 2.75 mg, respectively, vs. 4.37 mg), statistical analysis yielded no significance because of the small number of patients carrying these genotypes. A significantly lower maintenance dose was observed in the subgroup of heterozygous *1/*3 genotype patients (p = 0.022). These preliminary results suggest a significant association of the CYP2C9 polymorphism with the warfarin dose and underline the importance of pre-therapeutic genotyping to identify the subjects likely to develop undesirable drug effects.
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Affiliation(s)
- Elizabeta Topić
- Clinical Institute of Chemistry, School of Medicine, Sestre milosrdnice University Hospital, Zagreb, Croatia.
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20
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Kerdpin O, Elliot DJ, Boye SL, Birkett DJ, Yoovathaworn K, Miners JO. Differential contribution of active site residues in substrate recognition sites 1 and 5 to cytochrome P450 2C8 substrate selectivity and regioselectivity. Biochemistry 2004; 43:7834-42. [PMID: 15196026 DOI: 10.1021/bi0496844] [Citation(s) in RCA: 22] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022]
Abstract
Selected active site residues in substrate recognition sites (SRS) 1 and 5 of cytochrome P450 2C8 (CYP2C8) were mutated to the corresponding amino acids present in CYP2C9 to investigate the contribution of these positions to the unique substrate selectivity and regioselectivity of CYP2C8. The effects of mutations, singly and in combination, were assessed from changes in the kinetics of paclitaxel 6alpha-hydroxylation, a CYP2C8-specific pathway, and the tolylmethyl and ring hydroxylations of torsemide, a mixed CYP2C9/CYP2C8 substrate. Within SRS1, the single mutation S114F abolished paclitaxel 6alpha-hydroxylation, while the I113V substitution resulted in modest parallel reductions in K(m) and V(max). Mutations in SRS5 (viz., V362L, G365S, and V366L) reduced paclitaxel intrinsic clearance (V(max)/K(m)) by 88-100%. Torsemide is preferentially metabolized by CYP2C9, and it was anticipated that the mutations in CYP2C8 might increase activity. However, methyl and ring hydroxylation intrinsic clearances were either unchanged or decreased by the mutations, although hydroxylation regioselectivity was often altered relative to wild-type CYP2C8. The mutations significantly increased (28-968%) K(m) values for both torsemide methyl and ring hydroxylation but had variable effects on V(max). The effects of the combined mutations in SRS1, SRS5, and SRS1 plus SRS5 were generally consistent with the changes produced by the separate mutations. Mutation of CYP2C8 at position 359 (S359I), a site of genetic polymorphism in CYP2C9, resulted in relatively minor changes in paclitaxel- and torsemide-hydroxylase activities. The results are consistent with multiple substrate binding orientations within the CYP2C8 active site and a differential contribution of active site residues to paclitaxel and torsemide binding and turnover.
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Affiliation(s)
- Oranun Kerdpin
- Department of Clinical Pharmacology, Flinders University and Flinders Medical Centre, Adelaide, SA 5042, Australia
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21
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Hummel MA, Dickmann LJ, Rettie AE, Haining RL, Tracy TS. Differential activation of CYP2C9 variants by dapsone. Biochem Pharmacol 2004; 67:1831-41. [PMID: 15130760 DOI: 10.1016/j.bcp.2004.01.017] [Citation(s) in RCA: 21] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/30/2003] [Accepted: 01/20/2004] [Indexed: 11/24/2022]
Abstract
Studies have shown that CYP2C9.1 mediated metabolism of flurbiprofen or naproxen is activated by co-incubation with dapsone. However, dapsone activation has not been examined in the known variant forms of CYP2C9. Six concentrations of flurbiprofen (2-300microM) or naproxen (10-1800 microM) were co-incubated with six concentrations of dapsone (0-100 microM) and with reconstituted, purified CYP2C9.1, CYP2C9.2 (R144C), CYP2C9.3 (I359L), or CYP2C9.5 (D360E), in order to assess degrees of activation. Dapsone increased the efficiency (V(m)/K(m)) of flurbiprofen 4'-hydroxylation by CYP2C9.1, CYP2C9.2, CYP2C9.3, and CYP2C9.5 by 8-, 31-, 47-, and 22-fold, respectively. In similar experiments using the substrate naproxen, dapsone increased the efficiency of naproxen demethylation 7-, 15-, 13-, and 22-fold, in CYP2C9.1, CYP2C9.2, CYP2C9.3, and CYP2C9.5, respectively. Also, dapsone normalized naproxen's kinetic profile from biphasic (CYP2C9.1 and CYP2C9.2) or linear (CYP2C9.3 and CYP2C9.5) to hyperbolic for all variant forms. Thus, amino acid substitutions of CYP2C9 variants affect the degree of dapsone activation in a genotype-dependent fashion. Furthermore, the degree of effect noted across variants appeared to be dependent on the substrate studied.
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Affiliation(s)
- Matthew A Hummel
- Department of Basic Pharmaceutical Sciences, School of Pharmacy, West Virginia University, Morgantown, WV, USA
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22
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Freeman BD, McLeod HL. Challenges of implementing pharmacogenetics in the critical care environment. Nat Rev Drug Discov 2004; 3:88-93. [PMID: 14708023 DOI: 10.1038/nrd1285] [Citation(s) in RCA: 13] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/09/2023]
Affiliation(s)
- Bradley D Freeman
- Department of Surgery, Washington University School of Medicine, 660 S. Euclid Avenue, Box 8109, St Louis, Missouri 63110, USA.
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23
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Iida I, Miyata A, Arai M, Hirota M, Akimoto M, Higuchi S, Kobayashi K, Chiba K. CATALYTIC ROLES OF CYP2C9 AND ITS VARIANTS (CYP2C9*2 AND CYP2C9*3) IN LORNOXICAM 5′-HYDROXYLATION. Drug Metab Dispos 2004; 32:7-9. [PMID: 14709614 DOI: 10.1124/dmd.32.1.7] [Citation(s) in RCA: 19] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022] Open
Abstract
The effects of allelic variants of CYP2C9 (CYP2C9*2 and CYP2C9*3) on lornoxicam 5'-hydroxylation were studied using the corresponding variant protein expressed in baculovirus-infected insect cells and human liver microsomes of known genotypes of CYP2C9. The results of the baculovirus expression system showed that CYP2C9.3 gives higher K(m) and lower V(max) values for lornoxicam 5'-hydroxylation than does CYP2C9.1. In contrast, K(m) and V(max) values of CYP2C9.1 and CYP2C9.2 for the reaction were comparable. Lornoxicam 5'-hydroxylation was also determined in liver microsomes of 12 humans genotyped for the CYP2C9 gene (*1/*1, n = 7; *1/*2, n = 2; *1/*3, n = 2; *3/*3, n = 1). A sample genotyped as *3/*3 exhibited 8- to 50-fold lower intrinsic clearance for lornoxicam 5'-hydroxylation than did samples genotyped as *1/*1. However, the values for intrinsic clearance for *1/*3 were within the range of values exhibited by samples of *1/*1. In addition, no appreciable differences were observed in kinetic parameters for lornoxicam 5'-hydroxylation between *1/*1 and *1/*2. In conclusion, this study showed that lornoxicam 5'-hydroxylation via CYP2C9 was markedly decreased by the substitution of Ile359Leu (CYP2C9.3), whereas the effect of the substitution of Arg144Cys (CYP2C9.2) was nonexistent or negligible. Additional in vivo studies are required to confirm that individuals with homologous CYP2C9*3 allele exhibit impaired lornoxicam clearance.
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Affiliation(s)
- Izumi Iida
- Department of Drug Metabolism, Research Center, Taisho Pharmaceutical Co., Ltd., 403, Yoshino-cho 1-chome, Saitama-shi, Saitama 330-8530, Japan.
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24
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Abstract
Cytochrome p450 (CYP) 2C9 hydroxylates about 16% of drugs in current clinical use. Of special interest are those with a narrow therapeutic index, such as S-warfarin, tolbutamide and phenytoin, where impairment in CYP2C9 metabolic activity might cause difficulties in dose adjustment as well as toxicity. Single-nucleotide polymorphisms (SNP) in the CYP2C9 gene have increasingly been recognized as determinants of the metabolic phenotype that underlies interindividual and ethnic differences. Apart from the wild-type protein CYP2C9*1 at least five allelic variants produce allozymes with reduced or deficient metabolic activity. Among white populations only CYP2C9*2 and CYP2C9*3 variants are of significance, with allelic frequencies of 0.08-0.14 and 0.04-0.16, respectively. In contrast, in Africans (African-Americans and Ethiopians) and Asians both variants are much less frequent (0.005-0.04), and CYP2C9*2 has not yet been detected in Asians. CYP2C9*4 has been exclusively identified in Japanese patients, and CYP2C9*5 and *6 were only found among African-Americans with a low allelic frequency of 0.017 and 0.006, respectively. Furthermore in Japanese a CYP2C9 promotor variant of four linked SNPs was correlated with reduced intrinsic clearance of phenytoin in vitro. Subjects who are carriers of one or more variant alleles may be at risk for adverse drug reactions/toxicities when prescribed drugs extensively metabolized by CYP2C9.
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Affiliation(s)
- U I Schwarz
- Institute of Clinical Pharmacology, Medical Faculty, Technical University, Dresden, Germany.
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25
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Dorado P, Berecz R, Cáceres MC, LLerena A. Analysis of diclofenac and its metabolites by high-performance liquid chromatography: relevance of CYP2C9 genotypes in diclofenac urinary metabolic ratios. J Chromatogr B Analyt Technol Biomed Life Sci 2003; 789:437-42. [PMID: 12742136 DOI: 10.1016/s1570-0232(03)00137-5] [Citation(s) in RCA: 18] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/01/2022]
Abstract
In humans, diclofenac is metabolised to 4'-hydroxy (OH), 3'-OH and 5-OH metabolites. The polymorphic CYP2C9 is involved in the metabolism of diclofenac to 4'-OH diclofenac and 3'-OH diclofenac. The aim of the present study was to develop a high-performance liquid chromatographic method to simultaneously measure diclofenac and its metabolites in urine, suitable for metabolic studies. After liquid-liquid extraction the compounds were separated in a reversed-phase column and measured by ultraviolet absorption at 282 nm. For all compounds intra-day and inter-day variations were less than 7%, and the limits of quantitation were 0.25 mg/l. No analytical interference with endogenous compounds was found. The relationship between diclofenac metabolic ratios among different CYP2C9 genotypes is reported. The CYP2C9*3/*3 subject had the highest diclofenac/4'-OH ratios. However no difference was found between CYP2C9*2/*2 and *1/*1 genotypes. The chromatographic method developed was sensitive and reliable for the measurement of diclofenac and its metabolites simultaneously in human urine, and is suitable for use in diclofenac metabolism studies.
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Affiliation(s)
- Pedro Dorado
- Department of Pharmacology and Psychiatry, Faculty of Medicine, University of Extremadura, Badajoz, Spain
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26
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Lee CR, Pieper JA, Hinderliter AL, Blaisdell JA, Goldstein JA. Losartan and E3174 pharmacokinetics in cytochrome P450 2C9*1/*1, *1/*2, and *1/*3 individuals. Pharmacotherapy 2003; 23:720-5. [PMID: 12820813 DOI: 10.1592/phco.23.6.720.32187] [Citation(s) in RCA: 24] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/23/2022]
Abstract
STUDY OBJECTIVE To determine if differences in the pharmacokinetics of losartan and its pharmacologically active E3174 metabolite exist among individuals expressing the cytochrome P450 (CYP) 2C9*1/*1, *1/*2, and *1/*3 genotypes. DESIGN Single-dose pharmacokinetic study. SETTING University general clinical research center. SUBJECTS Fifteen healthy volunteers, five from each genotype: CYP2C9*1/*1, *1/*2, and *1/*3. INTERVENTION A single oral dose of losartan 50 mg. MEASUREMENTS AND MAIN RESULTS Plasma and urine samples were collected for 24 hours, and losartan and E3174 pharmacokinetic data were compared across the three genotypes. Orthostatic blood pressure was measured over 12 hours after dosing. No significant differences were observed among the three groups in losartan or E3174 area under the plasma concentration-time curve, losartan or E3174 elimination half-life, or losartan oral clearance. A significant association between CYP2C9 genotype and losartan to E3174 formation clearance was observed, such that 50% of the variability was accounted for by the genotype. No significant relationship between that genotype and blood pressure was observed at any time. CONCLUSION Differences in the pharmacokinetics of losartan and its active E3174 metabolite were not observed in healthy subjects with the genotype of CYP2C9*1/*2 and *1/*3 compared with those expressing *1/*1. Alterations in losartan dosing in CYP2C9*1/*2 and *1/*3 individuals does not appear necessary.
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Affiliation(s)
- Craig R Lee
- Division of Pharmacotherapy, University of North Carolina at Chapel Hill, 27599-7360, USA.
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Lee CR, Pieper JA, Frye RF, Hinderliter AL, Blaisdell JA, Goldstein JA. Differences in flurbiprofen pharmacokinetics between CYP2C9*1/*1, *1/*2, and *1/*3 genotypes. Eur J Clin Pharmacol 2003; 58:791-4. [PMID: 12698304 DOI: 10.1007/s00228-003-0574-6] [Citation(s) in RCA: 50] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/18/2002] [Accepted: 01/24/2003] [Indexed: 11/30/2022]
Abstract
OBJECTIVE This study was conducted to examine differences in flurbiprofen metabolism among individuals with the CYP2C9*1/*1, *1/*2, and *1/*3 genotypes. METHODS Fifteen individuals with the CYP2C9*1/*1 ( n=5), *1/*2 ( n=5), and *1/*3 ( n=5) genotypes received a single 50-mg oral dose of flurbiprofen. Plasma and urine samples were collected over 24 h, and flurbiprofen and 4'-hydroxyflurbiprofen pharmacokinetic data were compared across genotypes. RESULTS CYP2C9 genotype was a significant predictor of flurbiprofen metabolism and accounted for 59% of the variability in flurbiprofen AUC(0- infinity ), and approximately 50% of the variability in flurbiprofen oral clearance, formation clearance to 4'-hydroxyflurbiprofen, and the 0 to 24-h urinary metabolic ratio of flurbiprofen to 4'-hydroxyflurbiprofen. Flurbiprofen AUC(0- infinity )was significantly higher and all measures of flurbiprofen clearance were significantly lower in the CYP2C9*1/*3 individuals than in those with *1/*1. Significant differences in these parameters were not detected between *1/*2 subjects and *1/*1 subjects. CONCLUSIONS CYP2C9 genotype is a significant predictor of flurbiprofen disposition in humans by altering CYP2C9-mediated metabolism and reducing systemic clearance. The effects are most pronounced in individuals carrying the *3 allele.
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Affiliation(s)
- Craig R Lee
- Division of Pharmacotherapy, University of North Carolina at Chapel Hill, NC 27599-7360, Chapel Hill, USA.
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28
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Meisel C, Gerloff T, Kirchheiner J, Mrozikiewicz PM, Niewinski P, Brockmöller J, Roots I. Implications of pharmacogenetics for individualizing drug treatment and for study design. J Mol Med (Berl) 2003; 81:154-67. [PMID: 12682724 DOI: 10.1007/s00109-002-0417-4] [Citation(s) in RCA: 47] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/02/2002] [Accepted: 12/12/2002] [Indexed: 12/29/2022]
Abstract
Adverse drug reactions and ineffective drug treatment are responsible for a large health care burden. Considerable variability in drug response makes the prediction of the individual reaction difficult. Pharmacogenetics can help to individualize drug treatment in accordance with the genetic make-up of the patient. Drug response is best understood as a complex interplay between pharmacokinetics, pharmacodynamics, and other disease-associated factors. There are a large number of genetic variants in the enzymes of phase I and phase II drug metabolism, in drug transporters, and drug targets, all of which account for differences in drug response. The polymorphisms in the cytochrome P450 enzyme system have been investigated most extensively. Genotype-based dose adjustment which should ensure "bioequivalent" drug concentrations in all patients has been derived from pharmacokinetic parameters, but this approach will have to be verified in prospective studies. Drug transport has recently been recognized as a further crucial determinant in pharmacokinetics. The effect of genetics on disease susceptibility and drug treatment has been studied quite extensively; however, hardly any of this progress is at present reflected in routine health care. The integration of pharmacogenetic factors in clinical trials requires novel considerations for study design and data interpretation. It is to be hoped that the new science bioinformatics will (a) help us identify the contribution of genetics to disease and treatment response and will (b) create data-processing devices which help the physician in the face of the enormously expanding scientific knowledge in selecting the best individually adapted treatment for the patient.
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Affiliation(s)
- Christian Meisel
- Institute of Clinical Pharmacology, Berlin Center for Genome-Based Bioinformatics, University Hospital Charité, Humboldt University of Berlin, Schumannstrasse 20-21, 10098 Berlin, Germany.
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29
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Abstract
1. The application of a range of established and emerging technologies and experimental approaches has allowed investigation of cytochrome P450 (CYP) and uridine diphosphate-glucuronosyltransferase (UGT) at the functional, structural and molecular levels to address questions of therapeutic relevance, particularly the wide interindividual variability in metabolic clearance characteristic of drugs and chemicals metabolized by these enzymes. 2. Studies in vivo initially identified the various factors that contribute to interindividual variability. Subsequently, human liver microsomal kinetic approaches, together with the cloning and functional characterization of recombinant CYP and UGT isoforms, led to the development of in vitro strategies that allowed the qualitative prediction of those factors likely to alter the metabolic clearance of a given compound in vivo. More recently, computer (in silico) modelling has been used to complement the laboratory based procedures. 3. The application of molecular biological approaches additionally allowed identification of the mutations responsible for CYP and UGT genetic polymorphism and, in some instances, the domains and individual amino acids that confer isoform substrate and inhibitor selectivities. Homology models, developed using X-ray crystallographic data as the template, potentially enable prediction of the functional consequences of altered CYP structure. 4. The rapid advances occurring in genomics, proteomics, gene expression analysis and computer modelling will allow further unravelling of the complexities of drug metabolism and improved prospects for the individualization of drug therapy.
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Affiliation(s)
- John O Miners
- Department of Clinical Pharmacology, Flinders Medical Centre and Flinders University School of Medicine, Bedford Park, South Australia, Australia.
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30
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Burian M, Grösch S, Tegeder I, Geisslinger G. Validation of a new fluorogenic real-time PCR assay for detection of CYP2C9 allelic variants and CYP2C9 allelic distribution in a German population. Br J Clin Pharmacol 2002; 54:518-21. [PMID: 12445031 PMCID: PMC1874480 DOI: 10.1046/j.1365-2125.2002.01693.x] [Citation(s) in RCA: 45] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022] Open
Abstract
AIMS The aim was to develop a fast detection method for the polymorphic alleles related to impaired CYP2C9-mediated metabolism. METHODS CYP2C9 genotypes were identified in 118 DNA samples using real-time PCR (LightCycler) followed by melting curve analysis. All samples were re-tested by validated PCR-RFLP methodology. RESULTS The concordance between the two methods was 100% for two variant alleles. The frequencies of CYP2C9*1 (wild type), CYP2C9*2 and CYP2C9*3 (with 95% confidence intervals) were 0.81(0.05), 0.14(0.04) and 0.05(0.03), respectively, and are similar to those observed in other Caucasian populations. CONCLUSIONS This assay is simple and rapid and may be used for CYP2C9-genotyping in a clinical setting.
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Affiliation(s)
- Maria Burian
- Pharmazentrum Frankfurt, Institut für Klinische Pharmakologie, Klinikum der J.W. Goethe-Universität, Theodor-Stern-Kai 7, 60590 Frankfurt am Main, Germany
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Walles M, Thum T, Levsen K, Borlak J. Verapamil: new insight into the molecular mechanism of drug oxidation in the human heart. J Chromatogr A 2002; 970:117-30. [PMID: 12350087 DOI: 10.1016/s0021-9673(02)00641-6] [Citation(s) in RCA: 21] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/01/2022]
Abstract
Verapamil is a commonly prescribed cardiovascular drug, but surprisingly its metabolism in the target tissue of pharmacotherapy is basically unknown. We therefore investigated its biotransformation in human heart tissue and correlate the production of metabolites with the gene expression of major drug metabolising enzymes. Using electrospray LC-MS-MS and LC-MS3 experiments, a total of nine metabolites were observed in incubation experiments with verapamil and microsomes isolated from the human heart tissue, and this included a carbinolamine-, N-formyl-, ahemiacetale-, and formate-intermediate of N-demethyl- and O-demethylverapamil. We also observed a hydroxylation product at the benzylic position of atom C-7 (M9). Metabolites M5-M9 are novel and were not observed in previous studies with liver or other human tissues. A fine example of the considerable metabolic competence of human heart is the formation of M1-M4, e.g. dealkylverapamil, norverapamil and isomers of O-demethylverapamil, which were believed to be exclusively produced by the liver.
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Affiliation(s)
- Markus Walles
- Fraunhofer Institute of Toxicology and Aerosol Research, Center of Drug Research and Medical Biotechnology, Hannover, Germany
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Kerb R, Aynacioglu AS, Brockmöller J, Schlagenhaufer R, Bauer S, Szekeres T, Hamwi A, Fritzer-Szekeres M, Baumgartner C, Ongen HZ, Güzelbey P, Roots I, Brinkmann U. The predictive value of MDR1, CYP2C9, and CYP2C19 polymorphisms for phenytoin plasma levels. THE PHARMACOGENOMICS JOURNAL 2002; 1:204-10. [PMID: 11908757 DOI: 10.1038/sj.tpj.6500025] [Citation(s) in RCA: 111] [Impact Index Per Article: 5.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/09/2022]
Abstract
Phenytoin, an anticonvulsant, exhibits nonlinear pharmacokinetics with large interindividual differences. Because of its small therapeutic range with the risk of therapeutic failure or adverse drug effects in susceptible persons, therapeutic drug monitoring is frequently applied. The interindividual differences in dose response can partially be explained by known genetic polymorphisms in the metabolic enzyme CYP2C9 but a large deal of individual variability remains still unexplained. Part of this variability might be accounted for by variable uptake of phenytoin, which is a substrate of p-glycoprotein, encoded by the human MDR1 gene. We evaluated, whether phenytoin plasma levels correlate with a polymorphism in the MDR1 gene, C3435T, which is associated with intestinal PGP activity. Genotyping and analyses of plasma levels of phenytoin and metabolites in 96 healthy Turkish volunteers showed that the MDR1C > T3435 polymorphism affects phenytoin plasma levels (P = 0.064) and the metabolic ratio of p-HPPH vs phenytoin (MDR1*TT genotype, P = 0.026). The MDR1*CC genotype is more common in volunteers with low phenytoin levels (P < or = 0.001, chi2 test). A combined analysis of variable alleles of CYP2C9, 2C19 and MDR1 revealed that the number of mutant CYP2C9 alleles is a major determinant, the number of MDR1*T alleles further contributes to the prediction of phenytoin plasma levels and CYP2C19*2 does not explain individual variability. The regression equation that fitted the data best included the number of mutant CYP2C9 and MDR*T alleles as predictory variables and explained 15.4% of the variability of phenytoin data (r2 = 0.154, P = 0.0002). Furthermore, analysis of CYP2C9 and MDR1 genotypes in 35 phenytoin-treated patients recruited from therapeutic drug monitoring showed that combined CYP2C9 and MDR1 analysis has some predictive value not only in the controlled settings of a clinical trial, but also in the daily clinical practice.
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Affiliation(s)
- R Kerb
- Epidauros Biotechnology AG, Pharmacogenetics Laboratory, Bernried, Germany.
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Tracy TS, Hutzler JM, Haining RL, Rettie AE, Hummel MA, Dickmann LJ. Polymorphic variants (CYP2C9*3 and CYP2C9*5) and the F114L active site mutation of CYP2C9: effect on atypical kinetic metabolism profiles. Drug Metab Dispos 2002; 30:385-90. [PMID: 11901091 DOI: 10.1124/dmd.30.4.385] [Citation(s) in RCA: 67] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022] Open
Abstract
CYP2C9 wild-type protein has been shown to exhibit atypical kinetic profiles of metabolism that may affect in vitro-in vivo predictions made during the drug development process. Previous work suggests a substrate-dependent effect of polymorphic variants of CYP2C9 on the rate of metabolism; however, it is hypothesized that these active site amino acid changes will affect the kinetic profile of a drug's metabolism as well. To this end, the kinetic profiles of three model CYP2C9 substrates (flurbiprofen, naproxen, and piroxicam) were studied using purified CYP2C9*1 (wild-type) and variants involving active site amino acid changes, including the naturally occurring variants CYP2C9*3 (Leu359) and CYP2C9*5 (Glu360) and the man-made mutant CYP2C9 F114L. CYP2C9*1 (wild-type) metabolized each of the three compounds with a distinctive profile reflective of typical hyperbolic (flurbiprofen), biphasic (naproxen), and substrate inhibition (piroxicam) kinetics. CYP2C9*3 metabolism was again hyperbolic for flurbiprofen, of a linear form for naproxen (no saturation noted), and exhibited substrate inhibition with piroxicam. CYP2C9*5-mediated metabolism was hyperbolic for flurbiprofen and piroxicam but linear with respect to naproxen turnover. The F114L mutant exhibited a hyperbolic kinetic profile for flurbiprofen metabolism, a linear profile for naproxen metabolism, and a substrate inhibition kinetic profile for piroxicam metabolism. In all cases except F114L-mediated piroxicam metabolism, turnover decreased and the K(m) generally increased for each allelic variant compared with wild-type enzyme. It seems that the kinetic profile of CYP2C9-mediated metabolism is dependent on both substrate and the CYP2C9 allelic variant, thus having potential ramifications on drug disposition predictions made during the development process.
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Affiliation(s)
- Timothy S Tracy
- Deparment of Basic Pharmaceutical Sciences, School of Pharmacy, West Virginia University, Morgantown, West Virginia 26506, USA.
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Lee CR, Goldstein JA, Pieper JA. Cytochrome P450 2C9 polymorphisms: a comprehensive review of the in-vitro and human data. PHARMACOGENETICS 2002; 12:251-63. [PMID: 11927841 DOI: 10.1097/00008571-200204000-00010] [Citation(s) in RCA: 515] [Impact Index Per Article: 23.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/26/2022]
Abstract
The discovery of six distinct polymorphisms in the genetic sequence encoding for the cytochrome P450 2C9 (CYP2C9) protein has stimulated numerous investigations in an attempt to characterize their population distribution and metabolic activity. Since the CYP2C9*1, *2 and *3 alleles were discovered first, they have undergone more thorough investigation than the recently identified *4, *5 and *6 alleles. Population distribution data suggest that the variant *2 and *3 alleles are present in approximately 35% of Caucasian individuals; however, these alleles are significantly less prevalent in African-American and Asian populations. In-vitro data have consistently demonstrated that the CYP2C9*2 and *3 alleles are associated with significant reductions in intrinsic clearance of a variety of 2C9 substrates compared with CYP2C9*1; however, the degree of these reductions appear to be highly substrate-dependent. In addition, multiple in-vivo investigations and clinical case reports have associated genotypes expressing the CYP2C9*2 and *3 alleles with significant reductions in both the metabolism and daily dose requirements of selected CYP2C9 substrates. Individuals expressing these variant genotypes also appear to be significantly more susceptible to adverse events with the narrow therapeutic index agents warfarin and phenytoin, particularly during the initiation of therapy. These findings have subsequently raised numerous questions regarding the potential clinical utility of genotyping for CYP2C9 prior to initiation of therapy with these agents. However, further clinical investigations evaluating the metabolic consequences in individuals expressing the CYP2C9*2, *3, *4, *5, or *6 alleles are required before large-scale clinical genotyping can be recommended.
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Affiliation(s)
- Craig R Lee
- Division of Pharmacotherapy, University of North Carolina at Chapel Hill, 27599-7360, USA
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35
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Abstract
Genetic variability in drug response occurs as a result of molecular alterations at the level of drug-metabolising enzymes, drug targets/receptors, and drug transport proteins. In this paper, we discuss the possibility that therapeutic drug monitoring (TDM) in the future will involve not the mere measurement and interpretation of drug concentrations but will include both traditional TDM and pharmacogenetics-oriented TDM. In contrast to traditional TDM, which cannot be performed until after a drug is administered to the patient. pharmacogenetics-oriented TDM can be conducted even before treatment begins. Other advantages of genotyping over traditional TDM include, but are not limited to, the following: (i) it does not require the assumption of steady-state conditions (or patient compliance) for the interpretation of results; (ii) it can often be performed less invasively (with saliva, hair root or buccal swab samples); (iii) it can provide predictive value for multiple drugs [e.g. a number of cytochrome P450 (CYP) 2D6, CYP2C 19 or CYP2C9 substrates] rather than a single drug; (iv) it provides mechanistic, instead of merely descriptive, information; and (v) it is constant over an individual's lifetime (and not influenced by concurrent drug administration, alteration in hormonal levels or disease states). Pharmacogenetic information can be applied a priori for initial dose stratification and identification of cases where certain drugs are simply not effective. However, traditional TDM will still be required for all of the reasons that we use it now. In current clinical practice, pharmacogenetic testing is performed for only a few drugs (e.g. mercaptopurine, thioguanine, azathioprine, trastuzumab and tacrine) and in a limited number of teaching hospitals and specialist academic centres. We propose that other drugs (e.g. warfarin, phenytoin, codeine, oral hypoglycaemics, tricyclic antidepressants, aminoglycosides, digoxin, cyclosporin, cyclophosphamide, ifosfamide, theophylline and clozapine) are potential candidates for pharmacogenetics-oriented TDM. However, prospective studies of phaymacogenetics-oriented TDM must be performed to determine its efficacy and cost effectiveness in optimising therapeutic effects while minimising toxicity. In the future, in addition to targeting a patient's drug concentrations within a therapeutic range, pharmacists are likely to be making dosage recommendations for individual drugs on the basis of the individual patient's genotype. As we enter the era of personalised drug therapy, we will be able to identify not only the best drug to be administered to a particular patient, but also the most effective and safest dosage from the outset of therapy.
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Affiliation(s)
- M H Ensom
- Faculty of Pharmaceutical Sciences, The University of British Columbia, Vancouver, Canada.
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Kirchheiner J, Bauer S, Meineke I, Rohde W, Prang V, Meisel C, Roots I, Brockmöller J. Impact of CYP2C9 and CYP2C19 polymorphisms on tolbutamide kinetics and the insulin and glucose response in healthy volunteers. PHARMACOGENETICS 2002; 12:101-9. [PMID: 11875364 DOI: 10.1097/00008571-200203000-00004] [Citation(s) in RCA: 140] [Impact Index Per Article: 6.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 12/13/2022]
Abstract
Tolbutamide is known to be metabolized by cytochrome P450 2C9 (CYP2C9), and the effects of the CYP2C9 amino acid polymorphisms *2 (Arg144Cys) and *3 (Ile359Leu) could be important for drug treatment with tolbutamide and for use of tolbutamide as a CYP2C9 test drug. Tolbutamide pharmacokinetics and plasma insulin and glucose concentrations were studied in 23 healthy volunteers with all six combinations of the CYP2C9 alleles *1, *2 and *3, including two subjects with the combined CYP2C9*1/*1 and CYP2C19*2/*2 genotype. Volunteers received a single oral dose of 500 mg tolbutamide, followed by 75 g oral glucose at 1, 4.5 and 8 h after tolbutamide administration. Pharmacokinetic analysis was performed using a computer program for regression analysis of nonlinear mixed effects models. The mean oral clearances of tolbutamide were 0.97 (95% confidence interval [CI] 0.89-1.05), 0.86 (95% CI 0.79-0.93), 0.75 (95% CI 0.69-0.81), 0.56 (95% CI 0.51-0.61), 0.45 (95% CI 0.41-0.49) and 0.15 (95% CI 0.14-0.16) l/h in carriers of CYP2C9 genotypes 1/*1, *1/*2, *2/*2, *1/*3, *2/*3 and *3/*3, respectively. Tolbutamide pharmacokinetics in carriers of the functionally deficient CYP2C19*2/*2 genotype were not different from those in the CYP2C19 highly active genotype. Elimination in the six CYP2C9 genotype groups could be expressed as the linear combination of three constants (0.05, 0.04, 0.01 h(-1), which were specific to the respective CYP2C9 alleles *1, *2 and *3, thus indicating a co-dominant mode of inheritance. Insulin and glucose concentration-time curves did not change with differing CYP2C9 genotypes. Tolbutamide was confirmed as a substrate of the genetically polymorphic enzyme CYP2C9. The pronounced differences in pharmacokinetics due to the amino acid variants did not significantly affect plasma insulin and glucose concentrations in healthy volunteers.
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Affiliation(s)
- Julia Kirchheiner
- Institute of Clinical Pharmacology, University Medical Center Charité, Humboldt University, Berlin, Germany
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Tabrizi AR, Zehnbauer BA, Borecki IB, McGrath SD, Buchman TG, Freeman BD. The frequency and effects of cytochrome P450 (CYP) 2C9 polymorphisms in patients receiving warfarin. J Am Coll Surg 2002; 194:267-73. [PMID: 11893129 DOI: 10.1016/s1072-7515(01)01163-2] [Citation(s) in RCA: 65] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022]
Abstract
BACKGROUND Warfarin sodium (warfarin) is commonly prescribed in surgical practice. Warfarin use is complicated by an unpredictable dose response that may be due in part to genetically determined differences in metabolic capacity. To better understand the interaction between genotype and response to warfarin therapy, we determined the frequency and functional effects of polymorphisms of the predominant cytochrome P450 subfamily responsible for warfarin metabolism (eg, CYP2C9) in an ethnically defined U.S. patient population. DESIGN Patients requiring chronic anticoagulation with warfarin sodium (warfarin) were recruited over an 11-month period (June 1999 through May 2000) from the inpatient and outpatient divisions of a tertiary care medical center in this prospective observational study. Clinical and demographic information was collected and CYP2C9 genotype was determined. RESULTS One hundred fifty-three patients receiving warfarin therapy for at least four weeks and comprising two ethnic groups [33 African Americans (22%) and 120 Caucasians (78%)] were genotyped. The mean weekly warfarin dose (+/-SEM) for all patients [36.9 (+/- 1.5) mg] was not influenced by gender [85 males (56%), 68 females (44%)] or ethnicity (p>0.05 for both), but was significantly affected by age (p = 0.006 for weight adjusted warfarin dose). The frequencies of CYP polymorphisms were as follows: 2C9*2 (24/153) 15.7%, 2C9*3 (23/153) 15.0%. There were no gender differences in polymorphism frequency (CYP2C9*2 frequency = (13/ 85) 15.3% in males, (12/68) 17.6% in females, p=0.74; CYP2C9*3 frequency = (15/85) 17.6% in males and (8/68) 11.8% in females, p = 0.38). CYP polymorphisms were much less common in African Americans than Caucasians [(5/33) 15.2% versus (47/120) 39.2%, respectively p = 0.05)]. Patients with CYP polymorphisms (2C9*2, 2C9*3) had significantly lower warfarin doses compared to patients with wild-type genotypes [30.6 (+/- 2.5) mg versus 40.1 (+/- 1.7) mg, p = 0.0021] . Stepwise backward regression analysis suggested a moderate ability to predict warfarin dose based on CYP genotype (r2 = 0.26), p < 0.01). CONCLUSIONS CYP2C9 polymorphisms are common, associated with significant reductions in warfarin dose, and partly account for interpatient variability in warfarin sensitivity. As interactions between genetic factors and other variables that influence warfarin effect are more completely understood, CYP analysis may prove a useful adjunct for increasing the safety and efficacy of this agent.
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Affiliation(s)
- Arash Rafii Tabrizi
- Department of Surgery, Washington University School of Medicine, St Louis, MO, 63110, USA
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38
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Abstract
Warfarin is one of the most widely prescribed oral anticoagulants. However, optimal use of the drug has been hampered by its >10-fold interpatient variability in the doses required to attain therapeutic responses. Pharmacogenetic polymorphism of cytochrome P450 (CYP) may be associated with impaired elimination of warfarin and exaggerated anticoagulatory responses to the drug in certain patients. Clinically available warfarin is a racemic mixture of (R)- and (S)-warfarin, and the (S)-enantiomer has 3 to 5 times greater anticoagulation potency than its optical congener. Both enantiomers are eliminated extensively via hepatic metabolism with low clearance relative to hepatic blood flow. CYP2C9 is almost exclusively responsible for the metabolism of the pharmacologically more active (S)-enantiomer. Several human allelic variants of CYP2C9 have been cloned, designated as CYP2C9*1 (reference sequence or wild-type allele), CYP2C9*2, CYP2C9*3 and CYP2C9*4, respectively. The allelic frequencies for these variants differ considerably among different ethnic populations. Caucasians appear to carry the CYP 2C9*2 (8 to 20%) and CYP2C9*3 (6 to 10%) variants more frequently than do Asians (0% and 2 to 5%, respectively). The metabolic activities of the CYP2C9 variants have been investigated in vitro. The catalytic activity of CYP2C9*3 expressed from cDNA was significantly less than that of CYP2C9*1. Human liver microsomes obtained from individuals heterozygous for CYP2C9*3 showed significantly reduced (S)-warfarin 7-hydroxylation as compared with those obtained from individuals genotyped as CYP2C9*1. The influence of the CYP2C9*3 allele on the in vivo pharmacokinetics of (S)-warfarin has been studied in Japanese patients. Patients with the homozygous CYP2C9*3 genotype, as well as those with the heterozygous CYP2C9*1/*3 genotype, had significantly reduced clearance of (S)-warfarin (by 90 and 60%, respectively) compared with those with homozygous CYP2C9*1. The maintenance dosages of warfarin required in Japanese patients with heterozygous and homozygous CYP2C9*3 mutations were significantly lower than those in patients with CYP2C9*1/*1. In addition, 86% of British patients exhibiting adequate therapeutic responses with lower maintenance dosages of warfarin (<1.5 mg/day) had either the CYP2C9*2 or CYP2C9*3 mutation singly or in combination, whereas only 38% of randomly selected patients receiving warfarin carried the corresponding mutations. Furthermore, the former group showed more frequent episodes of major bleeding associated with warfarin therapy. These data indicate that the CYP2C9*3 allele may be associated with retarded elimination of (S)-warfarin and the resulting clinical effects. However, relationships between CYP2C9 genotype, enzyme activity, metabolism of probe substrates, dosage requirements and bleeding complications should be interpreted with caution, and further studies are required.
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Affiliation(s)
- H Takahashi
- Department of Pharmacotherapy, Meiji Pharmaceutical University, Kiyose, Tokyo, Japan.
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Bloch A, Ben-Chetrit E, Muszkat M, Caraco Y. Major bleeding caused by warfarin in a genetically susceptible patient. Pharmacotherapy 2002; 22:97-101. [PMID: 11794436 DOI: 10.1592/phco.22.1.97.33491] [Citation(s) in RCA: 11] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/23/2022]
Abstract
A 90-year-old woman was hospitalized for gastrointestinal bleeding. Although she had been receiving only warfarin 5 mg/day, her international normalized ratio (INR) was 66. Warfarin was discontinued, and her INR fell to 3.7 after transfusion of fresh-frozen plasma. However, it rose again spontaneously to 7.5. Eleven days after the last dose of warfarin had been administered, it was still detectable in the patient's plasma, indicating that impaired warfarin clearance may have caused an enhanced anticoagulation effect. Genetic analysis of the cytochrome P450 (CYP) isoenzyme 2C9, which mediates the major deactivating pathway of S-warfarin, revealed that the patient was a compound heterozygote carrying two variant alleles: CYP2C9*2 and CYP2C9*3. The patient's enhanced sensitivity to warfarin 5 mg/day can be ascribed to decreased clearance of S-warfarin secondary to genetic alteration of the gene encoding CYP2C9, resulting in a life-threatening complication.
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Affiliation(s)
- Aharon Bloch
- Division of Medicine, Hadassah University Hospital, Jerusalem, Israel
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Lin JH, Lu AY. Interindividual variability in inhibition and induction of cytochrome P450 enzymes. Annu Rev Pharmacol Toxicol 2001; 41:535-67. [PMID: 11264468 DOI: 10.1146/annurev.pharmtox.41.1.535] [Citation(s) in RCA: 162] [Impact Index Per Article: 7.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/09/2022]
Abstract
Drug interactions have always been a major concern in medicine for clinicians and patients. Inhibition and induction of cytochrome P450 (CYP) enzymes are probably the most common causes for documented drug interactions. Today, many pharmaceutical companies are predicting potential interactions of new drug candidates. Can in vivo drug interactions be predicted accurately from in vitro metabolic studies? Should the prediction be qualitative or quantitative? Although some scientists believe that quantitative prediction of drug interactions is possible, others are less optimistic and believe that quantitative prediction would be very difficult. There are many factors that contribute to our inability to quantitatively predict drug interactions. One of the major complicating factors is the large interindividual variability in response to enzyme inhibition and induction. This review examines the sources that are responsible for the interindividual variability in inhibition and induction of cytochrome P450 enzymes.
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Affiliation(s)
- J H Lin
- Department of Drug Metabolism, Merck Research Laboratories, West Point, Pennsylvania 19486, USA
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Xie HG, Kim RB, Wood AJ, Stein CM. Molecular basis of ethnic differences in drug disposition and response. Annu Rev Pharmacol Toxicol 2001; 41:815-50. [PMID: 11264478 DOI: 10.1146/annurev.pharmtox.41.1.815] [Citation(s) in RCA: 391] [Impact Index Per Article: 17.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/09/2022]
Abstract
Ethnicity is an important demographic variable contributing to interindividual variability in drug metabolism and response. In this rapidly expanding research area many genetic factors that account for the effects of ethnicity on pharmacokinetics, pharmacodynamics, and drug safety have been identified. This review focuses on recent developments that have improved understanding of the molecular mechanisms responsible for such interethnic differences. Genetic variations that may provide a molecular basis for ethnic differences in drug metabolizing enzymes (CYP 2C9, 2C19, 2D6, and 3A4), drug transporter (P-glycoprotein), drug receptors (adrenoceptors), and other functionally important proteins (eNOS and G proteins) are discussed. A better understanding of the molecular basis underlying ethnic differences in drug metabolism, transport, and response will contribute to improved individualization of drug therapy.
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Affiliation(s)
- H G Xie
- Division of Clinical Pharmacology, Department of Medicine, Vanderbilt University School of Medicine, Nashville, Tennessee 37232-6602, USA.
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Abstract
This article introduces pharmacogenetics and pharmacogenomics in the context of pharmacotherapy in the pediatric ICU setting. As an independent discipline (if it can be considered as such), pediatric or developmental pharmacogenetics is essentially at a neonatal stage. Available pharmacokinetic data derived from studies of drugs that are largely dependent on a single CYP pathway for their elimination provide initial assessments of the developmental profile of that particular CYP isoform. Essentially then, pharmacogenetics in a pediatric context refers to the changes in phenotype that occur as a child grows and develops. Furthermore, the apparent drug biotransformation "phenotype" may be influenced by disease (infection), environmental factors (diet and environmental contaminants) and concurrent medications; however, drug response is a function of the complex interplay among genes involved in drug transport, drug biotransformation, receptors, and signal transduction processes, among others. Therefore, optimization of pediatric pharmacotherapy necessarily requires that developmental changes in each of these areas and not just drug biotransformation be investigated thoroughly before the promise of pharmacogenetics and pharmacogenomics for rational therapeutics can be realized in children.
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Affiliation(s)
- J S Leeder
- Section of Developmental Pharmacology and Experimental Therapeutics, Division of Clinical Pharmacology and Toxicology, Children's Mercy Hospital and Clinics, University of Kansas Medical Center, Kansas City, Kansas, USA.
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Martin JH, Begg EJ, Kennedy MA, Roberts R, Barclay ML. Is cytochrome P450 2C9 genotype associated with NSAID gastric ulceration? Br J Clin Pharmacol 2001; 51:627-30. [PMID: 11422024 PMCID: PMC2014482 DOI: 10.1046/j.0306-5251.2001.01398.x] [Citation(s) in RCA: 42] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022] Open
Abstract
AIMS The aim of this study was to explore whether genetic variation of cytochrome P450 2C9 (CYP2C9) contributes to NSAID-associated gastric ulceration. The hypothesis tested was that CYP2C9 poor metabolizer genotype would predict higher risk of gastric ulceration in patients on NSAIDs that are metabolized by CYP2C9, due to higher plasma NSAID concentrations. METHODS Peripheral blood DNA samples from 23 people with a history of gastric ulceration attributed to NSAIDs metabolized by CYP2C9, and from 32 people on NSAIDs without gastropathy, were analysed to determine CYP2C9 genotype. RESULTS The following genotypes were found: *1/*1 (wild type) in 70% of cases and 58% of controls, *1/*2 in 17% of cases and 29% of controls, *1/*3 in 13% of cases and 13% of controls. The difference between case and control nonwild-type genotype frequency was 11.5% (95% CI -14,37%), with the direction of the difference being against the hypothesis. No individuals with homozygote poor metaboliser genotype were identified. The differences in genotype frequencies between the two groups were not significant and the frequencies were similar to those in a large published population study. Ninety-five percent binomial confidence interval analysis confirms that there is no apparent clinically significant relationship between CYP2C9 genotype and risk of gastric ulceration although a small difference in risk in poor metabolizers cannot be excluded. CONCLUSIONS These results do not support the hypothesis that gastric ulceration resulting from NSAID usage is linked to the poor metabolizing genotypes of CYP2C9.
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Affiliation(s)
- J H Martin
- Department of Clinical Pharmacology, Christchurch Hospital, New Zealand
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44
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Nelson MH, Birnbaum AK, Remmel RP. Inhibition of phenytoin hydroxylation in human liver microsomes by several selective serotonin re-uptake inhibitors. Epilepsy Res 2001; 44:71-82. [PMID: 11255075 DOI: 10.1016/s0920-1211(00)00203-5] [Citation(s) in RCA: 33] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/19/2022]
Abstract
Several case reports have indicated that the selective serotonin re-uptake inhibitor (SSRI) fluoxetine increases phenytoin blood levels when given concurrently. The mechanism of this drug-drug interaction has been attributed to inhibition of CYP2C9-catalyzed hydroxylation of phenytoin to its major oxidative metabolite in humans, para-hydroxyphenyl phenyl hydantoin (HPPH). With a bank of human liver microsomes (HLM), four SSRIs (fluoxetine, norfluoxetine, sertraline, and paroxetine) were tested for inhibition of HPPH formation. Initially, the K(m) and V(max) values of phenytoin hydroxylation to HPPH were determined in the individual HLM samples. The average K(m) (n=8) was 9.7+/-2.9 microM. The V(max) varied fivefold, with an average value of 113+/-53 pmol HPPH/min/nmol CYP450. All of the SSRIs inhibited HPPH formation; resulting Ki values were 31.1+/-10.1 microM (fluoxetine) (n=5), 51.1+/-9.4 microM (norfluoxetine) (n=3), 52.2+/-21.5 microM (sertraline) (n=3), and 80.0+/-7.2 microM (paroxetine) (n=3). Sulfaphenazole (10 microM), utilized as a positive control for inhibition of HPPH formation, inhibited phenytoin hydroxylation (>95%) in all HLM samples. Diclofenac hydroxylation to 4'-OH diclofenac, a specific marker for CYP2C9 activity, was determined in HLM1-HLM6 and was highly correlated with HPPH formation in HLM1-HLM6, indicating that phenytoin hydroxylation in human liver microsomes is largely due to CYP2C9. This work presents direct evidence that the effect of fluoxetine on phenytoin blood levels may be explained by inhibition of CYP2C9-catalyzed phenytoin hydroxylation. In light of typical SSRI blood levels observed in patients, this study also suggests that the risk of a SSRI-phenytoin interaction is highest with fluoxetine and norfluoxetine, and less likely with sertraline and paroxetine.
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Affiliation(s)
- M H Nelson
- Department of Medicinal Chemistry, College of Pharmacy, University of Minnesota, 8-101 WDH, 308 Harvard Street, S.E., Minneapolis, MN 55455, USA
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45
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Tang C, Shou M, Rushmore TH, Mei Q, Sandhu P, Woolf EJ, Rose MJ, Gelmann A, Greenberg HE, De Lepeleire I, Van Hecken A, De Schepper PJ, Ebel DL, Schwartz JI, Rodrigues AD. In-vitro metabolism of celecoxib, a cyclooxygenase-2 inhibitor, by allelic variant forms of human liver microsomal cytochrome P450 2C9: correlation with CYP2C9 genotype and in-vivo pharmacokinetics. PHARMACOGENETICS 2001; 11:223-35. [PMID: 11337938 DOI: 10.1097/00008571-200104000-00006] [Citation(s) in RCA: 82] [Impact Index Per Article: 3.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/26/2022]
Abstract
In-vitro studies were conducted to assess the impact of CYP2C9 genotype on the metabolism (methyl hydroxylation) and pharmacokinetics of celecoxib, a novel cyclooxygenase-2 inhibitor and CYP2C9 substrate. When compared to cDNA-expressed wild-type CYP2C9 (CYP2C9*1), the Vmax/Km ratio for celecoxib methyl hydroxylation was reduced by 34% and 90% in the presence of recombinant CYP2C9*2 and CYP2C9*3, respectively. These data indicated that the amino acid substitution at position 359 (Ile to Leu) elicited a more pronounced effect on the metabolism of celecoxib than did a substitution at position 144 (Arg to Cys). The Vmax/Km ratio was also decreased in microsomes of livers genotyped CYP2C9*1/*2 (47% decrease, mean of two livers), or CYP2C9*1/*3 (59% decrease, one liver). In all cases, these changes were largely reflective of a decrease in Vmax, with a minimal change in Km. Based on simulations of the in-vitro data obtained with the recombinant CYP2C9 proteins, it was anticipated that the pharmacokinetics of celecoxib (as a much as a five-fold increase in plasma AUC) would be altered (versus CYP2C9*1/*1 subjects) in subjects genotyped heterozygous or homozygous for the CYP2C9*2 (Cys144) or CYP2C9*3 (Leu359) allele. In a subsequent clinical study, the AUC of celecoxib was increased (versus CYP2C9*1/*1 subjects) approximately 2.2-fold (range, 1.6-3-fold) in two CYP2C9*1/*3 subjects and one CYP2C9*3/*3 subject receiving a single oral dose (200 mg) of the drug. In contrast, there was no significant change in celecoxib AUC in two subjects genotyped CYP2C9*1/*2.
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Affiliation(s)
- C Tang
- Drug Metabolism, Merck Research Laboratories, West Point, PA, USA.
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46
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Bhasker CR, McKinnon W, Stone A, Lo AC, Kubota T, Ishizaki T, Miners JO. Genetic polymorphism of UDP-glucuronosyltransferase 2B7 (UGT2B7) at amino acid 268: ethnic diversity of alleles and potential clinical significance. PHARMACOGENETICS 2000; 10:679-85. [PMID: 11186130 DOI: 10.1097/00008571-200011000-00002] [Citation(s) in RCA: 202] [Impact Index Per Article: 8.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/25/2022]
Abstract
UGT2B7 catalyses the glucuronidation of a diverse range of drugs, environmental chemicals and endogenous compounds. Hence, coding region polymorphisms of UGT2B7 are potentially of pharmacological, toxicological and physiological significance. Two variant UGT2B7 cDNAs encoding enzymes with either His or Tyr at residue 268 have been isolated. The variants, referred to as UGT2B7*1 and UGT2B7*2, respectively, arise from a C to T transversion at nucleotide 802 of the UGT2B7 coding region. Analysis of genomic DNA from 91 unrelated Caucasians and 84 unrelated Japanese demonstrated the presence of the variant alleles encoding UGT2B7*1 and UGT2B7*2 in both populations. However, while there was an approximately equal distribution of subjects homozygous for each allele in the Caucasian population, subjects homozygous for the UGT2B7*1 allele were over 10-fold more prevalent than UGT2B7*2 homozygotes in Japanese. The frequencies of the UGT2B7*1 and UGT2B7*2 alleles were 0.511 and 0.489, respectively, in Caucasians, and 0.732 and 0.268, respectively, in Japanese. The 95% confidence intervals for the two alleles did not overlap between Caucasians and Japanese. Rates of microsomal androsterone, menthol and morphine (3-position) glucuronidation were determined for genotyped livers from Caucasian donors. Statistically significant inter-genotypic differences were not apparent for any of the three substrates. Although the UGT2B7 polymorphism characterized here is probably not associated with altered enzyme activity, the results highlight the need to consider ethnic variability in assessing the consequences of UGT polymorphisms.
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Affiliation(s)
- C R Bhasker
- Department of Clinical Pharmacology, Flinders Medical Centre and Flinders University of SA, Adelaide, Australia
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47
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Freeman BD, Zehnbauer BA, McGrath S, Borecki I, Buchman TG. Cytochrome P450 polymorphisms are associated with reduced warfarin dose. Surgery 2000; 128:281-5. [PMID: 10923005 DOI: 10.1067/msy.2000.107283] [Citation(s) in RCA: 57] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022]
Abstract
BACKGROUND Warfarin use is complicated by an erratic dose response. Interpatient variability associated with warfarin therapy may be partly attributable to polymorphisms of the cytochrome P450 (CYP) complex. The purpose of this study was to ascertain the frequency and influence of CYP polymorphisms on warfarin dosing in our patient population. METHODS Patients receiving warfarin therapy were recruited from the inpatient divisions of our hospital. Genotyping for known polymorphic alleles of the CYP subfamilies CYP2C9 (CYP2C9*1, CYP2C9*2, and CYP2C9*3) and CYP2A6 (CYP2A6*1, CYP2A6*2) with the use of standard methods of polymerase chain reaction amplification was performed. An unpaired t test was used to statistically compare genotypes. RESULTS Genotype frequency in 38 patients is as follows: CYP2C9*1/CYP2C9*1, 71%; CYP2C9*1/CYP2C9*2, 21%; CYP2C9*2/CYP2C9*2, 3%; CYP2C9*1/CYP2C9*3, 5%; CYP2A6*1/CYP2A6*1, 95%; CYP2A6*1/CYP2A6*2, 5%. Compared to a wild-type genotype, the presence of the CYP2C9*2, CYP2C9*3, or CYP2A6*2 allele was associated with a significant reduction in weekly warfarin dose (mean weekly warfarin dose [+/- SE] for wild-type genotype was 0.397 +/- 0.024 mg/kg/wk vs 0.307 +/- 0.03 mg/kg/wk for carriers of CYP2C9*2, CYP2C9*3, or CYP2A6*2 polymorphism; P =.03). CONCLUSIONS Polymorphisms that impair warfarin metabolism are common, occurring in 34% of patients, and are associated with increased warfarin sensitivity. The use of genotypic information to prescribe more accurate doses of warfarin may increase the safety and efficacy of this medication.
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Affiliation(s)
- B D Freeman
- Departments of Surgery, Pathology, and Biostatistics, Washington University School of Medicine, St Louis, MO 63110, USA
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Ieiri I, Tainaka H, Morita T, Hadama A, Mamiya K, Hayashibara M, Ninomiya H, Ohmori S, Kitada M, Tashiro N, Higuchi S, Otsubo K. Catalytic activity of three variants (Ile, Leu, and Thr) at amino acid residue 359 in human CYP2C9 gene and simultaneous detection using single-strand conformation polymorphism analysis. Ther Drug Monit 2000; 22:237-44. [PMID: 10850388 DOI: 10.1097/00007691-200006000-00001] [Citation(s) in RCA: 59] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/26/2022]
Abstract
This study evaluated the catalytic activity of three variants (Ile, Leu, and Thr) at codon 359 of CYP2C9 enzymes expressed in a yeast cDNA expression system, and then established single-strand conformation polymorphism (PCR-SSCP) analysis for simultaneous detection as a screening method. Diclofenac was used for the in vitro experiment, and its hydroxy metabolite (4'-hydroxydiclofenac) was measured by HPLC. To discuss the in vivo effect of the Thr359 variant on the pharmacokinetics of phenytoin, a case report is presented. The efficiency of the SSCP method was evaluated by analyzing DNA samples from a homozygote for Ile359 and a heterozygote for Leu359 or Thr359. To evaluate the interaction between the P450 level and reductase activity, two batches of the Thr359 variant with a different P450:reductase activity ratio (1:4.0 and 1:1.4) were used. The in vitro study revealed that recombinant Ile359, Leu359, and Thr359 (2 batches) possessed a mean Km of 2.0, 16.5 and (3.8 and 2.9) micromol and Vmax of 12.4, 17.9 and (4.4 and 5.1) nmol/min/nmol P450, respectively. Although the magnitude of the change in catalytic efficiency for the Thr359 variant was close to that of the Leu359 variant, the effect of the two variants on diclofenac 4'-hydroxylation appears to be different because Leu359 variant was associated with a high Km, and Thr359 with a low Vmax. No significant differences in the kinetic data were observed between the two Thr359 enzymes, suggesting that low reductase activity in the Thr359 enzyme was not a major determinant in the present in vitro experiment. Estimated pharmacokinetic parameters of phenytoin obtained by the Bayesian method in an epileptic patient who was a heterozygote carrier for Thr359 variant were: Km = 6.45 microg/mL, Vmax = 5.77 mg/kg/d, and Vmax/Km = 0.89 L/kg/day. The Vmax/Km value in this patient was similar to the population mean value (0.90 L/kg/day) in Japanese heterozygotes for the Leu359 variant. Results for PCR-SSCP were in complete agreement with those obtained using established methods. Thus, the PCR-SSCP approach is useful for identifying these three variants of the CYP2C9 gene.
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Affiliation(s)
- I Ieiri
- Department of Hospital Pharmacy, Faculty of Medicine, Tottori University, Yonago, Japan
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Miners JO, Coulter S, Birkett DJ, Goldstein JA. Torsemide metabolism by CYP2C9 variants and other human CYP2C subfamily enzymes. PHARMACOGENETICS 2000; 10:267-70. [PMID: 10803683 DOI: 10.1097/00008571-200004000-00008] [Citation(s) in RCA: 44] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/25/2022]
Affiliation(s)
- J O Miners
- Department of Clinical Pharmacology, Flinders Medical Centre and Flinders University School of Medicine, Adelaide, Australia.
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50
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Takanashi K, Tainaka H, Kobayashi K, Yasumori T, Hosakawa M, Chiba K. CYP2C9 Ile359 and Leu359 variants: enzyme kinetic study with seven substrates. PHARMACOGENETICS 2000; 10:95-104. [PMID: 10761997 DOI: 10.1097/00008571-200003000-00001] [Citation(s) in RCA: 205] [Impact Index Per Article: 8.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 12/12/2022]
Abstract
To assess the effects of Ile359 to Leu359 change on CYP2C9-mediated metabolism, we performed site-directed mutagenesis and cDNA expression in yeast for CYP2C9 and examined in detail the kinetics of seven metabolic reactions by wild-type CYP2C9 (Ile359) and its Leu359 variant. For the metabolism of all the substrates studied, the Leu359 variant exhibited smaller Vmax/Km values than did the wild-type. The differences in the Vmax/Km values between the wild-type and the Leu359 variant varied from 3.4-fold to 26.9-fold. The Leu359 variant had higher Km values than did the wild-type for all the reactions studied. Among the seven reactions studied, the greatest difference in the Vmax values between the wild-type and the Leu359 variant was for piroxicam 5'-hydroxylation (408 versus 19 pmol/min/nmol P450), whereas there were no differences in the Vmax values between the wild-type and the Leu359 variant for diclofenac 4'-hydroxylation and tolbutamide methylhydroxylation. These results indicate that the Ile359 to Leu359 change significantly decreases the catalytic activity of all the CYP2C9-mediated metabolisms studied, whereas the extent of the reduction in activity and changes of the kinetic parameters varies between substrates. Moreover, the amino acid substitution decreased the enantiomeric excess in the formation of 5-(4-hydroxyphenyl)-5-phenylhydantoin from phenytoin.
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Affiliation(s)
- K Takanashi
- Laboratory of Biochemical Pharmacology and Toxicology, Faculty of Pharmaceutical Sciences, Chiba University, Japan
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