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1.
《中南药学》2019,(2):294-298
目的调查维生素K环氧化物还原酶复合物亚基1(VKORC1)、细胞色素P450(CYP)2C9和CYP2C19的等位基因分布,不同等位基因变异的贡献和可能的基因-基因相互作用对华法林治疗的影响。方法共纳入492名患者,并对VKORC1、CYP2C9和CYP2C19的单核苷酸多态性进行基因分型。结果 CYP2C9*1等位基因与CYP2C19*2和CYP2C19*17(D'=1)完全连锁不平衡。表达为VKORC1 GA、VKORC1 AA、CYP2C9*2和CYP2C9*3的等位基因变异患者需要比表达为VKORC1 GG或CYP2C9*1的野生型患者更低的华法林剂量。华法林稳定剂量和INR> 5事件的CYP2C19等位基因各种变异之间差异无统计学意义。表达为CYP2C19*2/*2、CYP2C19*2/*17和CYP2C19*17/*17基因型患者倾向于比CYP2C19*1/*1基因型患者需要更高的华法林剂量。逐步回归分析显示,年龄和性别是华法林剂量的显著影响因素。在单变量一般线性模型分析中检测到CYP2C9和VKORC1对华法林剂量和INR> 5事件没有统计学意义上的相互作用。结论 VKORC1和CYP2C9的基因多态变体独立影响华法林剂量,而CYP2C19不影响华法林治疗。  相似文献   

2.
《中国药房》2017,(11):1581-1584
目的:了解基因多态性对华法林剂量的影响以及其在临床的应用研究,以期为华法林的精准用药提供参考。方法:查阅近年来国内外相关文献,对华法林基因多态性以及其在临床的应用研究进行归纳和总结。结果与结论:影响华法林剂量的主要基因为细胞色素P450(CYP)2C9和维生素K氧化物还原酶复合体1(VKORC1)。华法林主要由CYP2C9酶完成代谢,与其代谢最密切的突变型为CYP2C9*2和CYP2C9*3。携带CYP2C9*2、CYP2C9*3等位基因的患者比野生型CYP2C9*1/*1患者有更高的过度抗凝和出血风险,提示携带CYP2C9*2、CYP2C9*3等位基因的患者所需华法林的剂量低于野生型CYP2C9*1/*1患者。VKORC1的酶活性直接影响华法林的抗凝效果,VKORC1基因与华法林早期治疗的影响较大。CYP4F2、γ-谷氨酰基羟化酶(GGCX)、载体蛋白E(APOE)、微粒体环氧化物水纤酶编码基因(EPHX1)等基因与华法林的剂量均呈现一定的相关性。华法林基因检测的临床应用主要依据FDA建议的基因多态性与华法林初始剂量对照表和剂量计算公式,但与华法林的给药剂量相关的两项临床研究结果并不一致,检测基因并结合计算公式将华法林应用于临床是否具有意义仍存在争议。  相似文献   

3.
目的 研究细胞色素P450酶2C9(CYP2C9)及维生素K环氧化物还原酶复合体亚单位1(VKORCl)基因多态性对中国肺栓塞患者华法林维持剂量的影响.方法 对108例INR已稳定达标的中国肺栓塞患者,采用TaqMan MGB探针法,检测CYP2C9*2、*3位点和VKORCl-1639A>G位点基因型.记录患者的年龄、性别、体重、身高及华法林日平均剂量.结果 VKORCl -1639AG或GG基因型患者华法林稳定日均剂量明显高于AA基因型患者(5.81±1.93vs 3.33±1.11mg,P <0.001);CYP2C9*2或*3变异的患者华法林稳定日均剂量低于无变异的患者(2.57±1.31 vs 3.97±1.67mg,P<0.001);包括患者性别、年龄、身高、体重、CYP2C9和VKORC1基因型等因素在内的华法林稳定剂量预测模型可解释51.1%左右的华法林稳定剂量个体差异(R2=0.511,P<0.001).结论 CYP2C9和VKORC1基因型检测对指导中国肺栓塞患者个体化应用华法林有一定的临床意义.  相似文献   

4.
目的:观察CYP2C9和VKORC1基因多态性对新疆少数民族患者华法林初始抗凝效果的影响。方法:选择行心脏瓣膜置换术并首次服用华法林的少数民族患者100例,于每日16:00时给予华法林,起始剂量2.5mg/d,3d后根据国际标准化比值(INR)调整剂量。应用基因芯片法检测其CYP2C9、VKORC1-1639AG、VKORC1+1173CT基因多态性,并记录患者使用华法林的初始剂量和INR达标时间,观察患者发生INR>3.0以及严重出血或栓塞等不良事件的发生率。结果:100例患者中,VKORC1-1639AA(VKORC1+1173TT)型患者39例,VKORC1-1639AG(VKORC1+1173CT)型患者51例,VKORC1-1639GG(VKORC1+1173CC)型患者10例;CYP2C9基因*1*1型74例,*1*2型9例,*1*3型14例,*3*3型3例。CYP2C9基因*1*1和*1*2型患者的INR首次达标时间与华法林剂量均显著多于CYP2C9基因*1*3和*3*3型患者,差异有统计学意义(P<0.05);VKORC1-1639AG和GG基因型患者的INR首次达标时间与华法林剂量均显著多于VKORC1-1639AA基因型患者(P<0.05);仅VKORC1基因变异的患者的INR首次达标时间和用药剂量显著多于两个基因均无变异和仅CYP2C9基因变异的患者,差异有统计学意义(P<0.05)。结论:CYP2C9和VKORC1基因多态性是影响华法林抗凝效果的重要因素,新疆维吾尔族和哈萨克族患者CYP2C9和VKORC1基因型变异率高,在服用华法林前进行基因检测具有重要意义。  相似文献   

5.
华法林为香豆素类抗凝血药,广泛用于防治血栓栓塞性疾病。华法林治疗窗窄,剂量个体差异大,临床应用中易出现出血合并症。近年研究表明,华法林个体剂量差异与影响华法林代谢和作用的多个基因多态性如CYP2C9、VKORC等有关。本文回顾华法林的药物基因组学研究进展,为临床合理应用华法林提供参考。  相似文献   

6.
目的评价细胞色素P450酶2C9(CYP2C9)及维生素K环氧化物还原酶复合体亚单位1(VKORC1)基因多态性对中国肺栓塞患者华法林初始抗凝疗效的影响。方法初次服用华法林抗凝的中国肺栓塞患者95例,用TaqMan MGB探针法,检测CYP2C9*2、*3位点和VKORC1-1639A>G位点基因型。记录患者的年龄、性别、体重、身高、服用华法林后每次INR值等指标,并记录患者从服用华法林开始到INR首次达标的时间、INR首次达标时华法林总剂量和日平均剂量等指标。结果 VKORC1-1639AG/GG基因型患者比VKORC1-1639AA基因型患者INR首次达标时间明显延长(P<0.001),且INR首次达标时所服用的华法林总剂量和日均剂量均高于后者(P<0.001);CYP2C9*2或*3变异的患者在初始抗凝阶段发生INR超过治疗窗(INR>3)的比例较高。患者性别、年龄、体重、CYP2C9和VKORC1基因型等因素在内的华法林初始剂量预测模型可解释54.6%左右的华法林剂量个体差异(R2=0.546,P<0.001)。结论 CYP2C9和VKORC1基因型检测对指导中国肺栓塞患者初始抗凝阶段个体化应用华法林有一定的临床意义。  相似文献   

7.
摘要:目的:探讨CYP2C9和VKORC1基因多态性对老年房颤患者华法林稳定剂量的影响,建立适合汉族人群老年房颤患者的华法林给药模型,指导华法林个体化抗凝治疗。方法:对195例口服华法林抗凝的老年患者进行CYP2C9和VKORC1基因分型,比较不同基因型房颤老年患者华法林日均稳定剂量差异。采用多重线性回归分析法依据CYP2C9和VKORC1基因型、年龄、体表面积(BSA)、胺碘酮建立华法林稳定剂量计算公式。结果:国际标准化比值(INR)稳定在2.0~3.0之间时,CYP2C9*1/*1基因型患者日均华法林剂量(3.10±0.91) mg,显著高于CYP2C9*1/*3与CYP2C9*3/*3基因型患者的(2.10±0.89) mg和(1.25±0.00) mg; VKORC1-1639AA基因型患者日均华法林剂量(2.86±0.88) mg,显著低于VKORC1-1639GA/GG基因型患者的(3.68±0.88) mg和(6.38±0.91) mg(P<0.05)。通过多元线性回归分析得出华法林稳定剂量公式,建立的回归模型中包含年龄、BSA、胺碘酮、CYP2C9和VKORC1-1639基因型,该模型能解释约60.4%个体间华法林剂量差异。结论:基于CYP2C9和VKORC1基因多态性建立的华法林稳定剂量预测公式,能帮助指导华法林在老年房颤患者中的抗凝治疗。  相似文献   

8.
高菲  宋洪涛  曾志勇  冯英力 《中国药房》2010,(22):2053-2057
目的:探讨CYP2C9和VKORC1基因多态性对华法林稳定维持剂量和抗凝治疗的影响,为建立心脏机械瓣膜置换术后患者的华法林个体化给药模型提供依据。方法:应用聚合酶链式反应-限制性片段长度多态性(PCR-RFLP)方法检测福州地区119例心脏机械瓣膜置换术后患者CYP2C9*3、CYP2C9-65G/C和VKORC1-1639A/G基因多态性。收集性别、年龄、体质量信息,同时记录华法林的稳定维持剂量、达标天数,观察抗凝过量、不良反应等指标。结果:CYP2C9*3和CYP2C9-65G/C基因型与低华法林维持剂量相关,VKORC1-1639A/G基因型与高华法林维持剂量相关。CYP2C9杂合体组患者抗凝过量危险性增加,但出血的危险性没有增加;携带CYP2C9和VKORC1突变等位基因的患者,抗凝达稳态时间延长。结论:患者用药前进行CYP2C9和VKORC1基因型检查,预测华法林用药剂量,可减少抗凝过量的发生,缩短剂量调整的时间。  相似文献   

9.
朱晓静  周梁 《海峡药学》2020,32(1):99-102
目的分析心房颤动(AF)患者CYP2C9、VKORC1基因多态性与华法林药物敏感度的关系。方法根据华法林给药累计剂量,将27例AF患者分为低起效剂量组和高起效剂量组;根据达标时间,分为短起效时间组和长起效时间组。比较高、低起效剂量组和长、短起效时间组CYP2C9、VKORC1不同基因型华法林的起效剂量和起效时间。结果高、低起效剂量组rs1057910(CYP2C9*3)及长、短起效时间组VKORC1 rs9923231基因构成差异有统计学意义(P<0.05)。与AA基因型比较,CYP2C9 rs1057910 AC基因型华法林起效剂量降低,VKORC1 rs9923231 GA基因型华法林起效时间缩短(P<0.05)。华法林药物敏感度可分为低度敏感、中度敏感和高度敏感3种。结论应结合临床实际对口服华法林行抗凝治疗的AF患者进行CYP2C9、VKORC1基因多态性检测,以便从基因类型角度合理分配华法林剂量。  相似文献   

10.
目的 探讨VKORC1(-1639G/A)、CYP2C9*3、CYP4F2(rs2108622) 和CYP2C19*2 基因多态性在中国心房颤动群体中的表达,分析其对房颤患者华法林谷浓度及维持剂量的影响。 方法 收集75例房颤患者的华法林血样,采用HPLC-UV法测定其谷浓度,PCR-RFLP法检测VKORC1(-1639G/A)、CYP2C9*3、CYP4F2(rs2108622)和CYP2C19*2基因分型。明确基因多态性对华法林谷浓度及维持剂量的影响。结果 华法林稳态谷浓度在0.5~<1.0μg?mL-1 、1.0~2.0μg?mL-1 及超过2.0μg?mL-1范围时,其临床有效率(69.23%,82.6%,63.41%)显著高于0. 5μg?mL-1以下浓度范围(48.39%)(P<0.05),且0.5~<1.0μg?mL-1 及超过2.0μg?mL-1浓度范围华法林的临床有效率相近(P>0.05)。VKORC1(-1639G/A)、CYP2C9*3、CYP4F2(rs2108622) 和CYP2C19*2等位基因频率分别为8.65%、7.35%、20%、30%。VKORC1位点AA型、CYP4F2位点CC型患者华法林稳态谷浓度分别低于AG/GG及 CT/TT型患者(P<0.01),而CYP2C9*3、CYP2C19*2各基因型间对华法林稳态谷浓度无显著差异(P>0.05)。携带AG/GG、CT/ TT型和野生型(*1/*1)基因型的患者,华法林维持剂量分别高于携带AA型、CC型和杂合型(*1/*3)的患者(P <0.01),而CYP2C19*2各基因型间与华法林维持剂量无显著差异(P >0.05)。结论 VKORC1(-1639G/A)、CYP2C9*3、CYP4F2(rs2108622) 和CYP2C19*2基因多态性显著影响房颤患者华法林的维持剂量,且VKORC1(-1639G/A)、CYP4F2(rs2108622)基因多态性与房颤患者华法林谷浓度密切相关。  相似文献   

11.
Pharmacogenetics of oral anticoagulants   总被引:12,自引:0,他引:12  
Daly AK  King BP 《Pharmacogenetics》2003,13(5):247-252
There is wide interindividual variation in oral anticoagulant dose requirement, which is partly genetically determined. Several cytochrome P450s contribute to oxidative metabolism of oral anticoagulants. The most important of these is CYP2C9, which hydroxylates the S-enantiomers of warfarin, acenocoumarol and phenprocoumon with high catalytic activity. In at least eight separate clinical studies, possession of the CYP2C9*2 or CYP2C9*3 variant alleles, which result in decreased enzyme activity, has been associated with a significant decrease in a mean warfarin dose requirement. Several studies also suggest that possession of a CYP2C9 variant allele is associated with an increased risk of adverse events, such as bleeding. Possession of the CYP2C9*3 variant also appears to be associated with a low acenocoumarol dose requirement. Other genetic factors, such as polymorphisms in the cytochromes P450 that metabolize the R-enantiomers of warfarin and acenocoumarol, may also be relevant to anticoagulant dose. The molecular basis of anticoagulant resistance where a higher than normal dose of anticoagulant is required remains unclear, but could be due to unusually high CYP2C9 activity (pharmacokinetic resistance) or to an abnormality in the target enzyme vitamin K epoxide reductase (pharmacodynamic resistance).  相似文献   

12.
Cytochrome P450 2C9 (CYP2C9) is the enzyme that terminates the anticoagulant effect of warfarin. The heterozygous carriers of the two allelic variants CYP2C9*2 and CYP2C9*3 have been associated with impaired warfarin metabolism and a higher risk of haemorrhage. Only three CYP2C9 poor metabolizers (CYP2C9*3/CYP2C9*3) initiating warfarin treatment have so far been identified, all of them with a dramatic overdose occurring a few days after treatment initiation. Acenocoumarol, another coumarinic anticoagulant, has recently been shown to be metabolized by CYP2C9. We report, for the first time, two cases of dramatic overanticoagulation occurring in patients starting acenocoumarol treatment while taking recommended doses (4 mg/day). In both cases, the overdose was discovered at the first INR control with values above 9. Genotyping revealed that the two patients were homozygous for the CYP2C9*3 allele. Our report highlights the need for CYP2C9 genotyping before starting oral anticoagulants in order to prevent early overanticoagulation episodes.  相似文献   

13.
The primary aim of the present study was to evaluate the effect of the genotype of vitamin K epoxide reductase complex 1 (VKORC1) on warfarin dose requirements in Japanese pediatric patients. Forty-eight pediatric patients (0.42-19.25 years old) in whom stable anticoagulation was achieved by warfarin were enrolled in this study, and the polymorphic alleles of VKORC1 and CYP2C9 were determined for each subject. The relative impact of covariates on the anticoagulant effect of warfarin was evaluated by multiple regression analysis. It was found that VKORC1 genotype and age were major factors affecting the relationship between the weight-normalized warfarin dose and the therapeutic prothrombin time-international normalized ratio (PT-INR). Because only one patient had the CYP2C9*3 allele, we could not evaluate the effect of CYP2C9 polymorphisms on the anticoagulant effect of warfarin. In contrast, the anticoagulant effect of warfarin in patients with the VKORC1 1173CT or 1173CC genotype was 52.3% of that in patients with the 1173TT genotype. In addition, the anticoagulant effect of warfarin was shown to increase by 10.5% per year in Japanese pediatric patients. In conclusion, genotyping of VKORC1 will be useful in establishing individual anticoagulant therapy with warfarin, and it should be noted that a higher weight-normalized dose of warfarin is required in younger pediatric patients.  相似文献   

14.
The authors assessed the impact of CYP2C9*2, CYP2C9*3, and/or VKORC1-1639G>A/1173C>T single-nucleotide polymorphisms on oral anticoagulants in a Lebanese population. This study recruited 231 Lebanese participants on long-term warfarin or acenocoumarol maintenance therapy with an international normalized ratio (INR) monitored at the American University of Beirut Medical Center. CYP2C9 and VKORC1 variant alleles were screened by real-time PCR. Plasma R- and S-warfarin and R- and S-acenocoumarol levels were assayed using high-performance liquid chromatography. The variant allele frequencies of CYP2C9*2, CYP2C9*3, and VKORC1 -1639G>A/1173C>T were 15.4%, 7.8%, and 52.4%, respectively. Fifty-five participants were excluded from analysis because of nontherapeutic INR values at recruitment, leaving 43 participants taking warfarin and 133 taking acenocoumarol. There was a significant decrease in the weekly maintenance dose of both drugs with CYP2C9 and VKORC1 variants when compared with wild-type patients. CYP2C9*2 had the least impact on the response to both drugs. The concentrations of R- and S-warfarin in plasma were significantly correlated with CYP2C9 genotypes. For acenocoumarol, time to reach target INR was more prolonged in patients carrying any CYP2C9 variant allele but failed to reach statistical significance because of low numbers of patients. There was no association between allelic variants and bleeding events. This is the first pharmacogenetic study of oral anticoagulants in Arabs. The authors showed that both CYP2C9 and VKORC1 polymorphisms are common in Lebanon and influence warfarin and acenocoumarol dose requirements, with the CYP2C9*2 polymorphism having less effect on acenocoumarol, the most commonly used oral anticoagulant in Lebanon.  相似文献   

15.
Coumarin derivatives, including warfarin, acenocoumarol and phenprocoumon, are the drugs of choice for long-term treatment and prevention of thromboembolic events. The management of oral anticoagulation is challenging because of a large variability in the dose-response relationship, which is in part caused by genetic polymorphisms. The narrow therapeutic range may result in bleeding complications or recurrent thrombosis, especially during the initial phase of treatment. The aim of this review is to systematically extract the published data reporting pharmacogenetic influences on oral anticoagulant therapy and to provide empirical doses for individual genotype combinations. To this end, we extracted all data from clinical studies of warfarin, phenprocoumon and acenocoumarol that reported genetic influences on either the dose demand or adverse drug effects, such as bleeding complications. Data were summarized for each substance, and the relative effect of each relevant gene was calculated across studies, assuming a linear gene-dose effect in Caucasians. Cytochrome P450 (CYP) 2C9, which is the main enzyme for rate-limiting metabolism of oral anticoagulants, had the largest impact on the dose demand. Compared with homozygous carriers of CYP2C9*1, patients homozygous for CYP2C9*3 were estimated to need 3.3-fold lower mean doses of warfarin to achieve the same international normalized ratio, with *2 carriers and heterozygous patients in between. Differences for acenocoumarol and phenprocoumon were 2.5-fold and 1.5-fold, respectively. Homozygosity of the vitamin K epoxide reductase complex subunit 1 (VKORC1) variant C1173T (*2) allele (VKORC1 is the molecular target of anticoagulant action) was related to 2.4-fold, 1.6-fold and 1.9-fold lower dose requirements compared with the wild-type for warfarin, acenocoumarol and phenprocoumon, respectively. Compared with CYP2C9 and VKORC1 homozygous wild-type individuals, patients with polymorphisms in these genes also more often experience severe overanticoagulation. An empirical dose table, which may be useful as a basis for dose individualization, is presented for the combined CYP2C9/VKORC1 genotypes. Genetic polymorphism in further enzymes and structures involved in the effect of anticoagulants such as gamma-glutamylcarboxylase, glutathione S-transferase A1, microsomal epoxide hydrolase and apolipoprotein E appear to be of negligible importance.Despite the clear effects of CYP2C9 and VKORC1 variants, these polymorphisms explain less than half of the interindividual variability in the dose response to oral anticoagulants. Thus, while individuals at the extremes of the dose requirements are likely to benefit, the overall clinical merits of a genotype-adapted anticoagulant treatment regimen in the entire patient populations remain to be determined in further prospective clinical studies.  相似文献   

16.
We investigated the influence of genetic polymorphisms of CYP2C9 and VKORC1 genotypes on the pharmacokinetics and pharmacodynamics of warfarin and established an equation for predicting the maintenance dose of warfarin in the Thai population using genetic and non-genetic factors. The CYP2C9*2, CYP2C9*3, VKORC1 C1173T and VKORC1 G-1639A genotypes were detected by realtime PCR using fluorogenic hybridization probes. The associations between genetic and demographic factors with respect to warfarin dosage were analyzed. CYP2C9 polymorphisms affect warfarin metabolism as shown by a significant difference in warfarin clearance, whereas VKORC1 genotypes cause a significant difference in warfarin sensitivity index (INR:Cp). The mean weekly warfarin dose was significantly different among different VKORC1 and CYP2C9 genotypes. Patients with the VKORC1 BB haplotype and CYP2C9*1/*1 required about twice the warfarin dose compared to those with the VKORC1 AA haplotype and CYP2C9*1/*1. Using stepwise multiple linear regression, clinical factors (age and weight) and genetic factors (CYP2C9 and VKORC1) could explain about 53.8% of the variance of the warfarin maintenance dose. CYP2C9 and VKORC1 genotypes played an important role in the inter-individual variation in warfarin maintenance dose in a Thai population.  相似文献   

17.
Cytochrome P4502C9(CYP2C9) is largely responsible for terminating anticoagulant effect by hydroxylation of S-warfarin to inactive metabolites. Mutations in the CYP2C9 gene result in the expression of allelic variants, CYP2C9*2 and CYP2C9*3 with reduced enzyme activity compared to wild type CYP2C9*1. The aim of this study was to assess relationship between requirement of warfarin dose and polymorphism in CYP2C9 in Korean population. Patients on warfarin therapy for longer than 1 year were included from July 1999 to December 2000 and categorized as one of four groups; regular dose non-bleeding, regular dose bleeding, low dose non-bleeding and low dose bleeding. Low dose was defined as less than 10 mg/week for 3 consecutive monthly follow-ups. Bleeding complications included minor and major bleedings. Blood samples were processed for DNA extraction, genotyping and sequencing to detect polymorphism in CYP2C9. Demographic data, warfarin dose per week, prothrombin time (INR), indications and co-morbid diseases were assessed for each group. Total 90 patients on warfarin were evaluated; The low dose group has taken warfarin 7.6 +/- 1.7 mg/week, which was significantly lower than 31.4 +/- 0.9 mg/week in the regular dose group (p<0.0001). The measured INR in the low dose group was similar to that of the regular dose group (2.3 +/- 0.7 vs. 2.3 +/- 0.6, p=0.9). Even though there was a higher possibility of CYP2C9 variation in the low dose group, no polymorphism in CYP2C9 was detected. All patients were homozygous C416 in exon 3 for CYP2C9*2 and A1061 in exon 7 for CYP2C9*3. The DNA sequencing data confirmed the homozygous C416 and A1061 alleles. In conclusion, polymorphism in CYP2C9 is not a critical factor for assessing warfarin dose requirement and risk of bleeding complications in a Korean population.  相似文献   

18.
Vitamin K antagonists belong to the group of most frequently used drugs worldwide. They are used for long-term anticoagulation therapy, and exhibit their anticoagulant effect by inhibition of vitamin K epoxide reductase. Each drug exists in two different enantiomeric forms and is administered orally as a racemate. The use of vitamin K antagonists is complicated by a narrow therapeutic index and an unpredictable dose-response relationship, giving rise to frequent bleeding complications or insufficient anticoagulation. These large dose response variations are markedly influenced by pharmacokinetic aspects that are determined by genetic, environmental and possibly other yet unknown factors. Previous knowledge in this regard principally referred to warfarin. Cytochrome P450 (CYP) 2C9 has clearly been established as the predominant catalyst responsible for the metabolism of its more potent S-enantiomer. More recently, CYP2C9 has also been reported to catalyse the hydroxylation of phenprocoumon and acenocoumarol. However, the relative importance of CYP2C9 for the clearance of each anticoagulant substantially differs. Overall, the CYP2C9 isoenzyme appears to be most important for the clearance of warfarin, followed by acenocoumarol and, lastly, phenprocoumon. The less important role of CYP2C9 for the clearance of phenprocoumon is due to the involvement of CYP3A4 as an additional catalyst of phenprocoumon hydroxylation and significant excretion of unchanged drug in bile and urine, while the elimination of warfarin and acenocoumarol is almost completely by metabolism. Consequently, the effects of CYP2C9 polymorphisms on the pharmacokinetics and anticoagulant response are also least pronounced in the case of phenprocoumon; this drug seems preferable for therapeutic anticoagulation in poor metabolisers of CYP2C9. In addition to these vitamin K antagonists, oral thrombin inhibitors are currently under clinical development for the prevention and treatment of thromboembolism. Of these, ximelagatran has recently gained marketing authorisation in Europe. These novel drugs all feature some major advantages over traditional anticoagulants, including a wide therapeutic interval, the lack of anticoagulant effect monitoring and a low drug-drug interaction potential. However, they are also characterised by some pitfalls. Amendments of traditional anticoagulant therapy, including self-monitoring of international normalised ratio values or prospective genotyping for individual dose-tailoring may contribute to the continuous use of warfarin, phenprocoumon and acenocoumarol in the future.  相似文献   

19.
The effect of glimepiride on metabolism of S-warfarin to 7-hydroxywarfarin was studied using human liver microsomes and recombinant cytochrome P450 2C9 microsomes (CYP2C9.1 and CYP2C9.3), and was compared with the results from the experiments using glibenclamide as an inhibitor. S-Warfarin 7-hydroxylation by recombinant CYP2C9.1 and CYP2C9.3 was inhibited by glimepiride competitively. The apparent K(i) value of glimepiride was lower at CYP2C9.3 than at CYP2C9.1. Glimepiride also inhibited 7-hydroxylation of S-warfarin in a competitive manner by microsomes from human liver which showed the genotypes of CYP2C9, as CYP2C9*1/*1 or CYP2C9*1/*3. The apparent K(i) value of glimepiride was lower than that of glibenclamide. These results may provide valuable information for optimizing the anticoagulant activity of warfarin when glimepiride is co-administered to patients.  相似文献   

20.
CYP2C9 is involved in metabolism of nearly 25% of clinically used drugs. Coding region polymorphisms CYP2C9*2 and *3 contribute to interperson variability in drug dosage and clinical outcomes, whereas the role of a regulatory polymorphism remains uncertain. Measuring allelic RNA expression in 87 human liver samples, combined with genotyping, sequencing, and reporter gene assays, we identified a promoter variable number tandem repeat polymorphism (pVNTR) that fully accounted for allelic CYP2C9 mRNA expression differences. Present in three different variant forms [short (pVNTR-S), medium (pVNTR-M), and long (pVNTR-L)], only the pVNTR-S allele reduced the CYP2C9 mRNA level compared with the pVNTR-M (reference) allele. pVNTR-S is in linkage disequilibrium with *3, with linkage disequilibrium r(2) of 0.53 to 0.75 in different populations. In patients who were taking a maintenance dose of warfarin, the mean warfarin dose was associated with the copies of pVNTR-S (p = 0.0001). However, in multivariate regression models that included the CYP2C9*3, pVNTR-S was no longer a significant predictor of the warfarin dose (p = 0.60). These results indicate that although pVNTR-S reduced CYP2C9 mRNA expression, the in vivo effects of pVNTR-S on warfarin metabolism cannot be separated from the effects of *3. Therefore, it is not necessary to consider pVNTR-S as an additional biomarker for warfarin dosing. Larger clinical studies are needed to define whether the pVNTR-S has a minimal effect in vivo, or whether the effect attributed to *3 is really a combination of effects on expression by the pVNTR-S along with effects on catalytic activity from the nonsynonymous *3 variant.  相似文献   

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