内蒙古地区蒙古族VKORC1-1639 G/A和CYP2C9基因多态性与华法林应用剂量关系的研究

目的探讨内蒙古地区蒙古族维生素K环氧化物还原酶复合物1(VKORC1)-1639 G/A及CYP2C9基因多态性分布特点及对华法林应用剂量的影响。方法选择300例蒙古族心房颤动病人(蒙古族组)和300例汉族心房颤动病人(对照组),PCRRFLP法检测两组VKORC1-1639 G/A及CYP2C9基因型分布,同时记录华法林剂量及国际标准化比值(INR)。计算不同VKORC1及CYP2C9基因型间平均校正华法林剂量。结果蒙古族组VKORC1-1639 AA、AG、GG基因型分布频率分别为78%、18%、4%;等位基因A和G频率分别为87%、13%。对照组VKORC1-1639 AA、AG、GG基因型分布频率分别为79%、19%、2%;等位基因A和G频率分别为86%、14%。蒙古族CYP2C9*1/*1型276例,CYP2C9*1/*3型24例。汉族CYP2C9*1/*1型279例,CYP2C9*1/*3型21例。不同VKORC1、CYP2C9基因型房颤病人华法林用量不同,VKORC1 AA型并CYP2C9*1/*1型和VKORC1 AG型并CYP2C9*1/*1型病人华法林日用量均高于VKORC1 AA型并CYP2C9*1/*3型病人;VKORC1 AG型并CYP2C9*1/*1型病人华法林用量高于VKORC1 AA型并CYP2C9*1/*1型病人,3组比较,差异有统计学意义(P0.05)。结论蒙古族与汉族基因型VKORC1-1639 G/A及CYP2C9一致,多态性均为VKORC1-1639 AA及CYP2C9*1/*1型均占多数,不同基因型影响个体间华法林的维持应用剂量。     

CYP2C9和VKORC1基因多态性对高龄非瓣膜性心房颤动病人华法林维持剂量的影响

目的探讨细胞色素P450(CYP)2C9与维生素K环氧化物还原酶复合物1(VKORC1)基因多态性对高龄非瓣膜性心房颤动病人华法林维持剂量的影响。方法选取40例≥80岁非瓣膜性心房颤动病人为研究对象,记录病人的性别、年龄及华法林稳定给药剂量。采用数字荧光分子杂交测序技术检测病人的CYP2C9及VKORC1基因型,根据国际华法林药物基因组联合会(IWPC)公式计算出病人的华法林服用理论剂量。结果男性病人与女性病人的华法林日均剂量差异无统计学意义[(2. 16±0. 75)mg比(2. 00±0. 47)mg,P 0. 05]。CYP2C9-1075 A/C基因型中,AA型33例,CA型7例;AA型病人的华法林理论剂量明显高于CA型病人(P 0. 01);但两者的实际用量差异无统计学意义(P=0. 601)。VKORC1-1639 A/G基因型中,AA型33例,GA型7例;GA型病人的华法林理论剂量和实际用量均明显高于AA型病人(P 0. 05)。CYP2C9-1075 AA+VKORC1-1639 GA基因型病人的华法林实际用量明显高于CYP2C9-1075 CA+VKORC1-1639 AA基因型病人(P 0. 05),但其他组合基因型的华法林实际用量差异均无统计学意义(P 0. 05)。结论 VKORC1基因多态性是影响高龄老人华法林维持剂量的重要遗传因素,可根据病人基因型的不同合理分配华法林剂量。     

细胞色素氧化酶P4502 C9以及维生素K环氧化物还原酶复合体1基因多态性对华法林抗凝疗效的影响

目的 研究年龄、体重、身高、体表面积、细胞色素氧化酶P450(CYP2C9)和维生素K环氧化物还原酶复合体1(VKORC1)基因型与华法林剂量的关系.方法 收集临床使用华法林的患者共191例,记录患者的年龄、性别、身高、体重等.利用聚合酶链反应(PCR)和限制性内切酶片段长度多态性(RFLP)技术检测CYP2C9以及VKORC1基因型.结果 VKORC1(-1639G＞A)基因型检测有159例患者为突变纯合子AA型,31例患者为杂合子GA型,1例患者为纯合子GG型.CYP2C9基因型检测有176例患者为*1/*1型,15例患者为杂合子*1/*3型.VKORC1(-1639G＞A)GA+GG组,华法林平均剂量明显高于AA组[(3.36±0.97)mg/d比(1.75±0.56)mg/d,P＜0.01].CYP2C9*1/*1型患者华法林平均剂量高于杂合子*1/*3型患者[(2.06±0.83)mg/d比(1.55±1.32)mg/d,P＜0.05].多元线形回归分析提示年龄、体重以及VKORC1基因型分别解释了约9.3％、7.4％、51.9％的个体间剂量差异,包括年龄、体重、VKORC1和CYP2C9基因型的多变量模型能解释个体间剂量差异约为64.1％.结论 年龄、体重、VKORC1和CYP2C9基因多态性明显影响了华法林剂量.用年龄、体重、VKORC1和CYP2C9基因型的多变量模型给药方法希望提高华法林使用的安全性.     

VKORC1-1639G＞A、CYP2C9*3基因多态性及年龄、体质量对汉族肺血栓栓塞症患者华法林稳定剂量的影响

目的 探讨细胞色素P450酶2C9基因(CYP2C9)、维生素K环氧化物还原酶复合体亚单位1基因(VKORC1)多态性及非遗传因素对汉族肺血栓栓塞症患者华法林个体化用药的影响.方法 连续纳入北京安贞医院185例确诊为肺血栓栓塞症服用华法林治疗的汉族患者,且PT-INR值范围在2.0～3.0,服药时间至少3个月.采用聚合酶链反应-限制性片段长度多态性(PCR-RFLP)技术检测VKORC1-1639G＞A和CYP2C9*3基因型,通过多元逐步回归分析得出华法林稳定剂量的预测公式.结果 185例患者中,所需华法林稳定剂量差异较大,最小者为1.50 mg/d,最大者为7.50 mg/d.Spearman双变量秩相关分析显示:华法林稳定剂量与VKORC1-1639G＞A基因型(rs=0.482,P=0.000) 、CYP2C9*3基因型(rs=-0.244,P=0.001)及年龄(rs=-0.409,P=0.000)显著相关;性别(P=0.153)、身高(P=0.526)、体质量(P=0.075)、体表面积(P=0.085)及平均INR值(P=0.135)与华法林稳定剂量相关不明显.采用多元逐步回归分析得出华法林稳定剂量方程:D=5.802-1.780×(VKORC1-1639AG)-3.395×(VKORC1-1639AA)-0.027×Age+1.36×(CYP2C9*1/*1)+0.018×Weight.该方程可解释华法林稳定剂量个体差异总变异中的的51.7％.结论 VKORC1-1639G＞A和CYP2C9*3基因多态性及年龄、体质量是引起汉族肺血栓栓塞症患者个体间华法林剂量差异的因素.     

细胞色素P450亚型基因多态性分析及对华法林用药剂量的影响

目的探讨细胞色素P450亚型(CYP2C9)基因多态性与华法林抗凝治疗维持剂量的相关性。方法选择服用华法林的汉族患者200例,男性和女性各100例。患者均为心脏瓣膜置换术后。通过CAPS技术及常规DNA测序方法对CYP2C9基因的3个候选位点(CYP2C9*2、CYP2C9*3、CYP2C9*c65)进行测定。并分析携带不同基因患者华法林应用剂量差异。结果 200例患者中,并未检测到CYP2C9*2位点发生突变,仅检测到1种等位基因C,基因型全部为C/C野生型。检测到CYP2C9*3A和C位点,其中A/A野生型为171例,占85.5%;A/C杂合子突变型为18例,占9.0%;C/C纯合子突变型为11例,占5.5%。等位基因A频率为94.3%,等位基因C频率为5.7%。CYP2C9*3基因突变与服用华法林剂量存在显著差异(P0.05),A/C型患者服药剂量较A/A型患者降低了18.5%,C/C型患者服药剂量较A/A型降低了76.0%。CYP2C9*c65位点检测出G和C位点2种等位基因,G/G野生型182例,占91.0%;G/C杂合子突变型为18例,占9.0%;这2种基因突变患者的华法林维持剂量之间不存在明显相关性。结论 CYP2C9基因多态性与华法林抗凝治疗维持剂量有一定相关性。     

细胞色素P450酶和维生素K环氧化物还原酶复合体亚单位1基因多态性指导心房颤动患者华法林初始抗凝

目的:评价细胞色素P450酶(CYP2C9)和维生素K环氧化物还原酶复合体亚单位1(VKORC1)基因多态性,对阵发性心房颤动(房颤)射频消融术后患者华法林初始抗凝疗效的影响。方法:200例初次服用华法林的阵发性房颤射频消融术后患者,随机分成基因组和对照组(非基因对照组),基因组根据CYP2C9和VKORC1基因检测结果推荐剂量范围,从最低推荐剂量开始服用华法林。对照组按照华法林常规给药方式给药。计算服用华法林后INR值达2~3时两组所需的时间,及INR首次达标时华法林日平均剂量等指标。结果:两组INR达标时所需时间相比,基因组为(8.92±2.09)d,对照组为(11.91±2.18)d,(P0.05)。在基因组中,VKORC1-1639A/G或G/G的患者INR达标时华法林日平均剂量比VKORC1-1639A/A的患者多[(4.74±0.88)mg∶(3.42±0.60)mg,P0.05]。基因组中INR达标时的华法林日平均剂量与CYP2C9和VKORC1基因检测推荐范围相似。结论:VKORC1和CYP2CP基因检测指导可以缩短INR达标(INR 2~3)所需时间,对华法林平均日剂量的确定有一定作用,对指导阵发性房颤射频消融术后患者初始抗凝阶段,个体化应用华法林有一定的临床意义。     

少见细胞色素P4502C9等位基因对中国汉族心房颤动患者华法林稳态剂量的影响及预测模型的构建

目的:探究除细胞色素P450 2C9(CYP2C9)*2和CYP2C9*3以外的少见CYP2C9等位基因对中国汉族心房颤动患者华法林稳态剂量的影响,并构建新的预测模型。方法:选取2011年1月至2017年3月在我院接受华法林抗凝治疗的心房颤动患者681例,随机以2:1的比例分为建模组(n=454)和验证组(n=227)。采用PCR直接测序分析CYP2C9和维生素K环氧化物还原酶复合体1 (VKORC1)基因型,通过单因素相关分析筛选与华法林稳态剂量相关的变量,采用多元线性回归分析建立华法林稳态剂量预测模型。结果:发现了三种少见CYP2C9等位基因(CYP2C9*13、*16、*60),均为杂合子。综合这三种少见基因型,建立变量CYP2C9(13/16/60),其华法林稳态剂量显著低于CYP2C9*1/*1(P0.001)及CYP2C9*1/*3(P0.05)。构建中国汉族人群特异的包含有其他少见CYP2C9基因突变变量的华法林稳态剂量预测方程,华法林日剂量=exp[0.524+0.344×体表面积-0.082×胺碘酮-0.393×CYP2C9*3-0.740×CYP2C9(13/16/60)+0.276×VKORC1-1639GA+0.593×VKORC1-1639GG] R~2=44.3%。其中CYP2C9(13/16/60)占总基因型频率的0.7%,但可以解释6.3%的华法林剂量个体差异。将研究模型应用于验证组,相关系数达0.567。结论:CYP2C9*13、*16、*60等位基因与更低的华法林稳态剂量相关,新构建的纳入有上述少见CYP2C9等位基因变量的预测方程可以更好地预测中国汉族人群华法林稳态剂量。     

CYP2C9基因多态性对瓣膜置换术后华法林抗凝效果的影响

目的:评价CYP2C9基因多态性对二尖瓣和主动脉瓣联合瓣膜置换术后华法林抗凝效果的影响。方法:选择2014年10月至2017年3月,在我院接受联合瓣膜置换术的患者65例,随机分为自我检测组32例和标准检测组33例,分别给予凝血检测仪和定期门诊复诊监测INR,同时对所有患者进行VKORC1和CYP2C9基因型检测,比较不同基因型和监测方法对华法林剂量和INR达标的影响。结果:非CYP2C9*2/3组INR检测次数低于CYP2C9*2/3组(P0.05),而CYP2C9*2/3组TTR比例、华法林预计剂量及实际剂量均低于非CYP2C9*2/3组(P0.05),两组轻微出血事件比例组间比较,差异无统计学意义(P0.05);不同检测方法组TTR比例、超过TTR比例、低于TTR比例、INR测量次数、华法林预计剂量及实际剂量、轻微出血事件比例组间比较差异均无统计学意义(P0.05)。结论:CYP2C9*2和/或*3基因型增加联合瓣膜置换术后3个月华法林抗凝效果的不确定性,但不会增加心血管事件的发生率,同时INR自我检测不能改善TTR达标比例。     

心房颤动患者华法林药物敏感性与CYP2C9和VKORC1基因多态性的相关性

[摘要] 目的 对接受华法林抗凝治疗的心房颤动（房颤）患者进行CYP2C9和VKORC1基因多态性检测,分析CYP2C9和VKORC1基因多态性与华法林起效剂量和起效时间的相关性。方法 随机选取222例持续性房颤患者,根据抗凝治疗的结果进行分组。将患者华法林药物敏感性根据国际标准化比值（INR）达到目标值1.8～3.0时,华法林给药累计剂量<12.5mg为低起效剂量,≥12.5mg为高起效剂量,INR达到目标值1.8～3.0时达标时间<10天为短起效时间,≥10天为长起效时间,分析CYP2C9和VKORC1基因多态性与华法林起效剂量和起效时间的相关性。结果 （1）低起效剂量组患者年龄、血清肌酐（SCr）、游离甲状腺素（FT4）、服用β阻滞剂者显著高于高起效剂量组(P<0.05或0.01),体重指数（BMI）、白细胞（WBC）计数低于高起效剂量组(P<0.05),两组间CYP2C9 rs1057910基因构成存在显著差别(P<0.05)。（2）短起效时间组患者年龄、SCr、FT4、活化的部分凝血活酶时间（APTT）、脑钠肽（BNP）显著高于长起效时间组(P<0.05或0.01),BMI、WBC、左室射血分数（LVEF）低于长起效时间组(P<0.05或0.01),两组间VKORC1 rs9923231和rs10871454基因构成存在显著差别(P<0.05或0.01)。（3）CYP2C9 rs1057910 CA基因型华法林起效剂量显著低于AA基因型(P<0.01),VKORC1 rs9923231和rs10871454 CT基因型华法林起效时间显著短于TT基因型(P<0.05或0.01)。（4）根据CYP2C9和VKORC1不同基因型对华法林起效剂量和起效时间的不同影响,将华法林药物敏感性分为高度敏感、低度敏感和常规敏感预测模型。结论 CYP2C9和VKORC1基因多态性结合患者临床情况为指导临床合理使用华法林抗凝治疗提供了新的方法,以基因类型指导调节华法林剂量提供了依据。     

基因多态性对华法林低强度抗凝治疗稳定剂量影响的前瞻陛研究

目的 对影响华法林代谢及作用的多个相关基因进行测定,探讨其对中国人群低强度华法林抗凝稳定剂量的影响程度.方法 共纳入170名拟采取低强度华法林抗凝治疗患者,对其与华法林代谢及作用相关的3个基因CYP2C9（rs1057910）、VKORC1（rs9923231）、CYP4F2 （rs2108622）位点的基因多态性（SNP）进行检测,随后给予华法林治疗,目标国际标准化比值（INR）1.8-2.5,观察90天,同时记录患者的临床因素、INR值及华法林稳定剂量,分别判断临床及基因因素对华法林稳定剂量水平的影响作用.结果 CYP2C9、VKORC1、CYP4F2的5个SNP位点的SNP对华法林稳定剂量存在显著影响（P＜0.05）.经多元回归分析,年龄、体表面积、抗凝第4天INR值以及CYP2C9、VKORC1、CYP4F2 的SNP是华法林抗凝稳定剂量的独立影响因素;其中SNP可以独立解释18.6%的华法林稳定剂量的差异.结论 在目标强度为INR1.8-2.5的低强度华法林抗凝治疗中,CYP2C9（rs1057910）、VKORC1（rs9923231）、CYP4F2 （rs2108622）多态性对稳定剂量存在显著影响,可在临床工作中对上述3个SNP位点进行检测,对抗凝初期华法林的剂量进行预先调整.     

The impact of CYP2C9 and VKORC1 genetic polymorphism and patient characteristics upon warfarin dose requirements: proposal for a new dosing regimen

Current dosing algorithms do not account for genetic and environmental factors for warfarin dose determinations. This study investigated the contribution of age, CYP2C9 and VKORC1 genotype, and body size to warfarin-dose requirements. Studied were 297 patients with stable anticoagulation with a target international normalized ratio (INR) of 2.0 to 3.0. Genetic analyses for CYP2C9 (*2 and *3 alleles) and VKORC1 (-1639 polymorphism) were performed and venous INR and plasma R- and S-warfarin concentrations determined. The mean warfarin daily dose requirement was highest in CYP2C9 homozygous wild-type patients, compared with those with the variant *2 and *3 alleles (P < .001) and highest in patients with the VKORC1 (position -1639) GG genotype compared with those with the GA genotype and the AA genotype (P < .001). Mean warfarin daily dose requirements fell by 0.5 to 0.7 mg per decade between the ages of 20 to 90 years. Age, height, and CYP2C9 genotype significantly contributed to S-warfarin and total warfarin clearance, whereas only age and body size significantly contributed to R-warfarin clearance. The multivariate regression model including the variables of age, CYP2C9 and VKORC1 genotype, and height produced the best model for estimating warfarin dose (R2 = 55%). Based upon the data, a new warfarin dosing regimen has been developed. The validity of the dosing regimen was confirmed in a second cohort of patients on warfarin therapy.     

Frequency of VKORC1 (C1173T) and CYP2C9 genetic polymorphisms in Egyptians and their influence on warfarin maintenance dose: proposal for a new dosing regimen

Introduction: Warfarin is one of the most widely used anticoagulants, yet interindividual differences in drug response, a narrow therapeutic range and a high risk of bleeding or stroke complicate its use. We aimed to determine the allele and genotype frequency of VKORC1 1173 C>T, CYP2C9*2 and CYP2C9*3 variant polymorphisms in the Egyptian population and to evaluate their influence on the interindividual differences in warfarin dosage. Methods: A total of 154 unrelated healthy adult patients and 46 warfarin-treated patients were included. SYBR Green-based real-time polymerase chain reaction (PCR) assay was used for studying VKORC1 (C1173T) and CYP2C9*3 polymorphisms. Mutagenically separated PCR assay was used to detect the CYP2C9*2 allele. Results: VKORC1 genotype frequencies were 11%, 24% and 65% for CC, CT and TT, respectively. The prevalence of CYP2C9 haplotypes was 81% (*1\*1), 3.3% (*1\*2), 9.7% (*1\*3), 4.5% (*2\*2) and 0.65% (2\*3 and *3\*3). VKORC1 TT and CYP2C9*2\*2 were associated with a significantly lower warfarin dose. VKORC1 and CYP2C9 accounted for 31.7% and 15.6% of warfarin dose variability, respectively, and together with clinical factors explained 61.3% of total variability. Conclusion: VKORC1-TT and CYP2C9 *1/*1 are the most prevalent genotypes among Egyptians. Patients with VKORC1-TT genotype required a lower warfarin dose.     

The impact of age and CYP2C9 and VKORC1 variants on stable warfarin dose in the paediatric population

The influence of genetic variation on warfarin dose requirement is limited for paediatric patients. We performed a retrospective, cross‐sectional study to examine the effect of variant CYP2C9 and VKORC1 genotypes on warfarin dose in 100 children. Those with VKORC1 genotype AA required 48% of the dose of homozygous wild‐type (GG, P < 0·0001). Patients with any variant CYP2C9 allele required 71% of the dose for wild‐type (P = 0·001). The effect of variant VKORC1 alleles tended to vary with age, suggesting developmental ontogeny may influence warfarin sensitivity. Age, CYP2C9 genotype, VKORC1 genotype and age:VKORC1 interaction accounted for 53% of warfarin dose variability.     

Contribution of VKORC1 and CYP2C9 polymorphisms in the interethnic variability of warfarin dose in Malaysian populations

Within the Asian populations, Indian patients had been reported to require higher warfarin dose compared with the Chinese and Malay patients, and this could not entirely be explained by cytochrome P450 (CYP)2C9 gene variants. Genetic variants of vitamin K epoxide oxidase reductase complex subunit 1 (VKORC1) has been well established as one of key determinants in the different responses of warfarin amongst patients. Adult patients who attended an anticoagulation clinic with stable INR were recruited. VKORC1 and CYP2C9 genotype were sequenced, and clinical characteristics were assessed. A total of 91 Malays, 96 Chinese, and 46 Indian patients were recruited. The mean age was 55 years and 51.5% were males. The mean dose of warfarin for all patients was 3.7 mg, and the mean daily dose of warfarin was significantly higher in Indians compared with the Chinese and Malay patients, 4.9 versus 3.5 and 3.3 mg, respectively (p < 0.001). VKORC1 GG genotype was more commonly seen in Indian patients. The mean warfarin dose in patients with GG genotype required a significant higher warfarin dose compared with those with AG and AA genotype (4.9 vs. 3.7 vs. 3.1 mg, respectively; p < 0.001). CYP2C9*2 and *3 is associated with a lower maintenance dose, 2.9 versus 3.7 mg in CYP2C9*1; p < 0.01. In multivariate analysis, age, ethnic groups, and genotypes had a significant influence on the required warfarin dose. In conclusion, VKORC1 and CYP2C9 polymorphism contribute to the difference dose requirement amongst the patients but other additional possible factors may play a role in the Indian race.     

Polymorphisms in VKORC1 have more impact than CYP2C9 polymorphisms on early warfarin International Normalized Ratio control and bleeding rates

Poor warfarin control with resultant high International Normalized Ratios (INRs) and bleeding events is most common during the first months of treatment. The effects of genetic polymorphisms at the vitamin K epoxide reductase [VKORC1] and cytochrome P450 2C9 [CYP2C9] loci have been increasingly acknowledged as contributory factors of enhanced warfarin sensitivity. In our prospective, blinded study, 557 patients (49·1% male, mean age 65·4 years, range 18-91 years) commencing warfarin (target INR 2·5) were genotyped and monitored through the first 3 months of anticoagulation. Homozygosity for the -1639 G>A single nucleotide functional promoter polymorphism of the VKORC1 gene (genotype AA; 14·5% of cases) was associated with a significantly shortened time to therapeutic INR ≥ 2 (P < 0·01), reduced stable warfarin dose (P < 0·01), and an increased number of INRs > 5 (P < 0·001) and occurrence of bleeding events (P < 0·01) during the first month, as compared to the GG genotype. CYP2C9 genetic variations *2 and *3 were not associated with significant effect on these factors. Neither VKORC1 nor CYP2C9 polymorphisms influenced these parameters beyond the first month of treatment. These findings imply possible benefits of assessing VKORC1 polymorphisms prior to anticoagulation, particularly as a low dose induction regime in VKORC1 AA individuals appears to reduce the incidence of high INRs.     

Impact of CYP2C9*3, VKORC1-1639, CYP4F2rs2108622 genetic polymorphism and clinical factors on warfarin maintenance dose in Han-Chinese patients

To evaluate the impact of gene polymorphisms of Cytochrome P450 2C9 (CYP2C9), Vitamin K epoxide reductase complex subunit 1 (VKORC1) and Cytochrome P450 4F2 (CYP4F2) and clinical factors on warfarin maintenance dose in Han-Chinese patients from main land. DNA was extracted from 115 patients taking warfarin for more than 3 months with a stable international normalized ratio (INR) and genotyped for CYP2C9*3, VKORC1-1639 and CYP4F2 (rs2108622) polymorphisms using polymerase chain reaction-restriction fragment length polymorphism (PCR-RFLP). Univariate analysis and multiple regression analysis were undertaken to assess the effect of genetic and clinical factors on the warfarin maintenance dose. Our study demonstrated that patients carrying CYP4F2 CT or TT allele needed a significantly higher warfarin dose compared to those carrying CC ((3.36 ± 0.14 mg/d vs. 2.77 ± 0.14 mg/d), P = 0.004). We also confirmed CYP2C9 *3 variant was related to lower warfarin dose (2.01 ± 0.23 mg/d) requirement compared to wild type (3.21 ± 0.11 mg/d) (P = 0.001). VKORC1-1639 AG genotype was associated with a higher maintenance dose compared to those with the AA genotype (4.06 ± 0.21 mg/d vs. 2.95 ± 0.11 mg/d, P < 0.001). The multiple linear regression model including VKORC1-1639G>A, CYP2C9, CYP4F2 and clinical factors (body surface area (BSA) and age) could explain 42 % of the variance in the warfarin maintenance dose. We developed a dose algorithm based on genetic polymorphism and clinical variables for Han-Chinese patients and evaluated its performance. CYP4F2 rs2108622 has a small but significant association with warfarin stable dose in Han-Chinese population.     

The Influence of CYP2C9 and VKORC1 Gene Polymorphisms on the Response to Warfarin in Egyptians

Warfarin is the most commonly used drug for chronic prevention of thromboembolic events, it also ranks high among drugs that cause serious adverse events. The variability in dose requirements has been attributed to inter-individual differences in medical, personal, and genetic factor. Cytochrome P-450 2C9 is the principle enzyme that terminates the anticoagulant effect of warfarin by catalyzing the conversion of the pharmacologically more potent S-enantiomer to its inactive metabolites. Warfarin exerts its effect by inhibition of vitamin K epoxide reductase. This protein is encoded by vitamin K epoxide reductase complex subunit 1 gene (VKORC1). The current study aimed to investigate the pharmacogenetic effect of CYP2C9 and VKORC1 gene polymorphisms on the patients response to warfarin. One hundred cases starting warfarin treatment and 20 healthy controls were enrolled. The mean daily dose of warfarin was calculated from patient’s medical records. For each patient, less than 10 % variability in warfarin dose and a target international normalized ratio (INR) within the therapeutic target range were required for at least 3 months for one of the following indications (deep vein thrombosis, pulmonary embolism, cerebrovascular stroke and myocardial infarction) prior to inclusion in the study. Tetraprimer amplification refractory mutation system PCR was performed to determine CYP2C9*2, CYP2C9*3, and the VKORC1 1639 G > A genetic polymorphisms. Plasma warfarin determination was performed using rapid fluorometric assay. Plasma warfarin concentration ranged from 2.19 to 10.98 μg/ml with a median 3.52 μg/ml. Supratherpeutic INR was observed in 11 % of the cases. Thromboembolic complications occurred in 7 % of the cases and 8 % of cases experienced major bleeding. High maintenance dose (>7 mg/day) was associated with the combined non VKORC1*2 and homozygous wild type CYP2C9 (CYP2C9*1*1) alleles, while low maintenance dose was associated with the Variant (AG + AA)/Wild (*1/*1). (p value <0.001). CYP2C9 variant was a risk factor for supratherapeutic INR in the multivariate logistic regression model. Thromboembolic complication and incidence of supratherapeutic INR were observed in patients carrying combined VKORC1 Variant (AG + AA) and CYP2C9 Variant (*2/*3). Data from our study suggest that together with clinical factors, VKORC1 and CYP2C9 polymorphisms are important contributors to warfarin dosing and may help predict adverse effects in Egyptian patients.     

The effect of CYP2C9, VKORC1 and CYP4F2 polymorphism and of clinical factors on warfarin dosage during initiation and long-term treatment after heart valve surgery

The dosage of warfarin is restricted due to its narrow therapeutic index, so, the required dose must be adapted individually to each patient. Variations in warfarin dosage are influenced by genetic factors, the changes in patient diet, anthropometric and clinical parameters. To determine whether VKORC1 G3730A and CYP4F2 G1347A genotypes contribute to warfarin dosage in patients during initiation and long-term anticoagulation treatment after heart valve surgery. From totally 307 patients, who underwent heart valve surgery, 189 patients (62 %) who had been treated with warfarin more than 3 months, were included into the study. A hierarchical stepwise multivariate linear regression model showed, that during initiation clinical factors can explain 17 % of the warfarin dose variation. The addition of CYP2C9 and VKORC1 G-1639A genotype raises the accuracy about twice—to 32 %. The CYP4F2 G1347A genotype can add again about 2–34 %. During long-term treatment clinical factors explain about 26 % of warfarin dose variation. If the CYP2C9 *2, *3, VKORC1*2 alleles are detected, model can explain about 49 % in dose variation. The *3 allele of VKORC1 raises the accuracy by 1–50 %. The carriers of CYP4F2 A1347A genotype required higher daily warfarin doses during initiation of warfarin therapy after heart valve surgery than comparing to G/G and G/A carriers, but during the longer periods of warfarin use, the dosage of warfarin depended significantly on VKORC1 *3 allele (G3730A polymorphism) and on the thyroid stimulating hormone level in the blood plasma.     

Clinical significance of combined CYP2C9 and VKORC1 genotypes in Japanese patients requiring warfarin

The individual management of anticoagulation therapy is important for safe medical outcomes, including those of oral surgery. Here, Japanese patients who received warfarin (n = 35) and normal controls (n = 125) were analyzed by real-time PCR to determine the frequencies of single nucleotide polymorphisms in VKORC1 (vitamin K epoxide reductase complex, subunit 1) and CYP2C9 and how these frequencies related to warfarin dose and PT-INR. The genetic polymorphisms CYP2C9(*2) (416 C > T), CYP2C9(*3) (1061 A > C), and intron 1-136 C > T in VKORC1 (1173 C > T) were measured. All patients had the wild-type CYP2C9 gene (*1/*1). All 160 cases had the wild-type (CC) type CYP2C9(*2), 93.8% had AA type CYP2C9(*3), 6.2% had AC type CYP2C9(*3), 1.2% had CC type VKORC1, 13.8% had CT type VKORC1, and 85% had TT type VKORC1. The CC type VKORC1 genetic polymorphism was associated with a significantly higher mean warfarin maintenance dose (4.5 ± 0.5 mg) than other VKORC1 genotypes (TT type 2.9 ± 0.1 mg: CT type 3.4 ± 0.3 mg). Categorization of the patients in terms of the combined CYP2C9 and VKORC1 haplotype (the warfarin-responsive index; WRI) revealed the mean daily warfarin maintenance dose was 3.0 ± 0.1 mg for WRI 1 and 3.7 ± 0.3 mg for WRI 2 (P < 0.012). The event survey revealed 2 patients with nonfatal cerebral hemorrhage had a WRI score of 2 (VKORC1 C/T heterozygosity genotype). Thus, CYP2C9 and VKORC1 haplotype analysis allows prediction of warfarin maintenance dosage. The findings may provide a personalized use of warfarin in the field of oral surgery.