液相色谱-质谱-质谱联用法测定人血浆中氯诺昔康液相色谱-质谱-质谱联用法测定人血浆中氯诺昔康

目的建立测定人血浆中氯诺昔康的液相色谱-质谱-质谱联用法,并用于中国受试者口服氯诺昔康的体内药代动力学研究。方法血浆样品经液-液萃取后,以甲醇-水-甲酸(80∶20∶0.5)为流动相,吡罗昔康为内标,采用Zorbax XDB-C8柱分离,通过液相色谱串联质谱,以选择反应监测(SRM)方式进行检测。定量分析离子反应分别为m/z 372→121(氯诺昔康)和m/z 332→121(吡罗昔康)。结果线性范围为2.0～1 600 μg·L^-1,定量下限为2.0 μg·L^-1。18名受试者po氯诺昔康8 mg后主要药动学参数t_1/2为(4.7±1.1) h,AUC_0-∞为(5.5±2.4) mg·h·L^-1。而另一名受试者t_1/2为105 h,AUC_0-∞为189.5 mg·h·L^-1。结论该法灵敏度高,线性范围宽,操作简便、快速,适用于临床药代动力学研究。     

氯诺昔康体外孵育体系的建立及氯诺昔康代谢产物5 OH氯诺昔康的检测

摘 要 目的：建立一个以氯诺昔康为底物来研究CYP2C9*1在体外代谢活性的体系并利用UPLC MS/MS来检测氯诺昔康代谢产物,为临床上相关药物的合理用药提供依据。方法: 以氯诺昔康为底物,利用重组昆虫细胞微粒体体外孵育法,模拟与体外孵育相似的环境进行体外代谢,通过建立UPLC MS/MS检测氯诺昔康代谢产物,采用Graphpad prism 软件绘制米曼曲线,计算Km值和最大反应速度Vm,从而通过氯诺昔康来研究CYP2C9*1中的体外代谢活性。结果: 在最终确定的色谱条件下,氯诺昔康、其代谢产物及内标峰分离良好。Km值为1.201 μmol·L-1,最大反应速度Vmax值为0.276 2 pmol·min-1·mg-1。结论: 本研究通过UPLC MS/MS建立CYP2C9*1酶代谢活性检测方法,此方法方便快捷、灵敏性高、准确性好,适用于氯诺昔康代谢产物的测定研究。同时通过氯诺昔康建立了体外孵育体系,为CYP2C9*1酶代谢活性的研究提供了参考依据。     

浙江沿海汉族人群CYP2C9基因多态性与甲苯磺丁脲代谢活性关系

目的探讨浙江沿海地区汉族人群CYP2C9基因多态性与甲苯磺丁脲代谢关系。方法采用寡核苷酸基因芯片,对浙江沿海地区汉族人群137名健康志愿者进行基因分型;选择含有突变型等位基因CYP2C9*3志愿者和部分野生型志愿者共20名参加甲苯磺丁脲药代动力学试验;统计分析不同CYP2C9基因型个体的代谢参数。结果在137名健康受试者DNA标本中发现CYP2C9*1/*3杂合突变型个体9名,CYP2C9*3/*3纯合突变个体1名,未发现CYP2C9*2、*4和*53种突变型等位基因,其中本研究受试人群中CYP2C9等位基因频率CYP2C9*1/*1占92.7%,CYP2C9*1/*3占6.6%,CYP2C9*3/*3占0.7%。药物代谢显示,CYP2C9*3纯合子个体的药物清除率显著低于CYP2C9*1纯合子个体。CYP2C9*1/*3杂合突变型个体组及1名CYP2C9*3/*3纯合型突变个体组,甲苯磺丁脲的代谢显著慢于野生型个体组。野生型(*1/*1)个体组、*1/*3杂合型突变个体组及1名*3/*3纯合型突变个体组,甲苯磺丁脲的药物代谢动力学参数差异与基因分型结果一致。结论CYP2C9多态性是甲苯磺丁脲药物代谢临床表现复杂性的主要因素,建立高效可靠的药代酶基因分型方法对CYP2C9代谢相关药物的临床个体化医疗具有一定的指导作用。     

细胞色素P4502C9基因多态性对健康人体内格列喹酮药代动力学的影响

目的研究细胞色素CYP2C9基因多态性对中国人体内格列喹酮药物代谢动力学的影响。方法用RELP-PCR方法对38名健康受试者进行CYP2C9基因多态性检测,并按不同CYP2C9基因型进行分组,用高效液相色谱-荧光检测法测定受试者体内格列喹酮的血药浓度并计算相应的药代动力学参数,比较不同基因型受试者间药代动力学参数的差异。结果在38名健康受试者中,发现3名CYP2C9*1/*3杂合突变型个体与35名CYP2C9*1/*1野生型个体;未发现CYP2C9*3/*3纯合突变型个体。随机抽取的17名野生型个体与3名杂合突变型个体在给予格列喹酮60 mg后,发现杂合突变型个体AUC0-t、AUC0-∞、CL/F分别相当于野生型个体的1.854,1.787,0.554倍。结论 CYP2C9基因多态性对格列喹酮的药代动力学有显著影响,CYP2C9*1/*3突变型个体临床应适当调整给药剂量。     

鸡尾酒法评价石蒜对大鼠细胞色素P450酶活性的影响

目的 运用鸡尾酒法评价石蒜对细胞色素P450酶活性的影响。方法 将大鼠随机分为对照组和石蒜低、高剂量组。对照组给予生理盐水，石蒜低、高剂量组大鼠灌胃给药0.5，1.0 g·kg^-1石蒜，连续给药15 d。然后第16天给予探针药物，UPLC-MS/MS检测探针药浓度。结果 与对照组对比，石蒜低剂量组和高剂量组的安非他酮AUC_（0-t）、C_max都显著升高（P<0.05），CL_z/F显著降低（P<0.05）。与对照组对比，石蒜高剂量组的美托洛尔、咪达唑仑和非那西丁AUC_（0-t）显著降低（P<0.05）、CL_z/F显著升高（P<0.05），而低剂量组与对照组比较差异无统计学意义。与对照组对比，石蒜组的甲苯磺丁脲AUC_（0-t）、CL_z/F差异无统计学意义，C_max显著降低（P<0.05）。结论 石蒜能抑制大鼠CYP2B1酶活性，诱导大鼠CYP2D1、CYP3A2和CYP1A2酶活性，稍有诱导大鼠CYP2C11酶活性的作用。     

香叶木苷对格列苯脲在大鼠体内药动学的影响

目的 考察香叶木苷在大鼠体内对格列苯脲药动学的影响。方法 12只SD大鼠随机分为香叶木苷组和对照组，分别给予香叶木苷（325 mg·kg^-1，ig，qd）和同体积CMC-Na溶液7 d后，灌胃给予格列苯脲，于不同时间点采集血浆样品，测定血药浓度，DAS 2.0计算主要药动学参数，并进行统计学分析。结果 与对照组比，香叶木苷组C_max显著降低（P<0.05），t_max显著缩短（P<0.05），AUC_（0→t）和AUC_{（0→∞）}显著减少（P<0.05），CL显著增大（P<0.05），t_1/2差异不显著。结论 香叶木苷影响格列苯脲在大鼠体内的药动学过程，临床联合用药中应对格列苯脲的血药浓度进行监测，以避免潜在的药物相互作用风险。     

细胞色素P450 CYP2C9基因多态性对甲苯磺丁脲代谢动力学的影响

目的研究细胞色素P450 CYP2C9基因多态性对甲苯磺丁脲代谢动力学的影响。方法用基因芯片对137名健康志愿者进行CYP2C9基因多态性检测，将受试者分为CYP2C9野生型、杂合突变型和纯合突变型3组，用高效液相色谱法检测甲苯磺丁脲在受试者体内的药物代谢动力学参数，统计分析各组间药代动力学性质差异。结果在137名受试者中发现了9个CYP2C9*1/*3杂合型突变体和1个CYP2C9*3/*3纯合型突变体，其余为野生型个体。将9名CYP2C9*1/*3，1名CYP2C9*3/*3以及随机抽取的10名野生型个体分组，以甲苯磺丁脲为探药进行药物代谢动力学研究。结果在杂合型突变个体组以及纯合型突变个体组中，甲苯磺丁脲的代谢率显著低于对照的野生型个体组。结论CYP2C9基因多态性对甲苯磺丁脲代谢具有显著影响并呈基因剂量效应，检测突变型个体对指导临床合理用药和个体化医疗具有重要意义。     

黄豆苷元对不同基因型健康受试者氯沙坦药代动力学的影响

目的 探讨黄豆苷元对不同基因型健康受试者氯沙坦药代动力学的影响.方法 筛选中国男性健康受试者18名(CYP2C9*1/*1、CYP2C9*1/*3、CYP2C9*1/*13基因型各6名).执行双周期、自身前后对照方案,第一阶段随机分为对照组和试验组,受试者分别口服黄豆苷元片或安慰剂15 d,第15天两组受试者均口服氯沙...     

复方盐酸二甲双胍片在人体内药物动力学和生物等效性研究

目的 建立人血浆中盐酸二甲双胍的反相离子对高效液相色谱和格列本脲的液相色谱-质谱测定方法,研究复方盐酸二甲双胍片(盐酸二甲双胍250mg/格列本脲1.25mg×2片)相对于联合使用的盐酸二甲双胍片(500mg)和格列本脲片(2.5mg)在男性健康志愿者体内的药物动力学行为,评价其生物利用度和生物等效性。方法 采用双交叉随机实验设计:20名受试者交叉口服复方盐酸二甲双胍片2片或口服盐酸二甲双胍片与格列本脲片各1片,服药后于0.5、1.0、1.5、2.0、2.5、3.0、3.5、4.0、5.0、6.0、8.0、12、24、36h分别取血,分离血浆,分别依法测定盐酸二甲双胍和格列本脲的血药浓度。结果 测得口服复方盐酸二甲双胍片或联合使用盐酸二甲双胍片与格列本脲片后,盐酸二甲双胍的达峰时间分别为(2.0±0.7)h和(2.1±0.9)h,峰浓度分别为(1402.4±349.2)μg·L^-1和(1329.7±315.4)μg·L^-1,消除半衰期分别为(3.84±0.61)h和(4.26±0.96)h,AUC_0-24分别为(7292.7±1967.5)μg·L^-1和(7416.2±1843.9)μg·h·L^-1；格列本脲的达峰时间分别为(3.1±0.9)h 和(3.0±0.8)h，峰浓度(71.7±22.7)μg·L^-1和(70.3±20.7)μg·L^-1,消除半衰期分别为(5.05±2.01)h 和(4.78±1.64)h，AUC_0-24分别为(367.6±168.7)μg·L^-1和(352.6±144.7)μg·h·L^-1；以联合服用等剂量的盐酸二甲双胍片与格列本脲片为参比，以AUC_0-24计算得复方盐酸二甲双胍片之盐酸二甲双胍和格列本脲的相对生物利用度，分别为101.1%±28.5%和123.7%±82.9%。结论 建立的分析方法准确灵敏，测得数据可靠。统计学分析表明复方盐酸二甲双胍片与联合使用盐酸二甲双胍片和格列本脲片显生物等效。     

CYP2C9基因多态性对苯溴马隆药动学的影响

目的研究健康人体内不同细胞色素P450(CYP)2C9基因多态性对苯溴马隆药动学的影响。方法采用PCR-RFLP方法对120例健康志愿者进行了CYP2C9基因多态性筛查,其中20例参加苯溴马隆药动学试验。用高效液相色谱法检测受试者体内苯溴马隆的药动学参数,分析不同的CYP2C9基因分型药动学参数的差异。结果 120例志愿者中筛选出9例CYP2C9*1/*3杂合型突变体、1例CYP2C9*3/*3纯合型突变体和110例CYP2C9*1/*1野生型个体。9例CYP2C9*1/*3、1例CYP2C9*3/*3突变型(突变型组)和10例CYP2C9*1/*1(野生型组)志愿者参加了苯溴马隆的药动学试验。CYP2C9*3的等位基因频率为7.5%。突变型组的ρmax、t1/2、AUC0-24均高于野生型组,而CL/F低于野生型组,差异均具有统计学意义(P<0.05)。苯溴马隆给药24 h后,CYP2C9*1/*1野生型、CYP2C9*1/*3杂合突变型和CYP2C9*3/*3纯合突变型志愿者尿酸清除较服药前分别增加了130%、90%和75%,血尿酸浓度较服药前分别减少了60%、43%和41%;突变型组与野生型组相比,差异具有统计学意义(P<0.05)。结论 CYP2C9基因多态性对苯溴马隆的代谢具有显著的影响,苯溴马隆在CYP2C9*3突变个体的代谢显著低于CYP2C9*1野生型个体,检测突变型个体对指导临床个体化用药具有重要意义。     

Lornoxicam pharmacokinetics in relation to cytochrome P450 2C9 genotype

AIMS: To investigate the pharmacokinetics of lornoxicam and the relationship with CYP2C9 polymorphism in healthy Chinese subjects. METHODS: A single oral dose of 8 mg lornoxicam was administered to 18 healthy Chinese male subjects. Plasma was sampled for 24 h post dose, and plasma concentrations of lornoxicam were measured using a validated LC/MS/MS method. CYP2C9 genotype was determined by polymerase chain reaction-based restriction fragment length polymorphism or by direct sequencing of the coding region of the CYP2C9 gene. RESULTS: Of the 18 subjects, one subject was found to be a very poor metabolizer of lornoxicam with a long t(1/2) of 106 h, a low CL/F of 0.71 ml min(-1), and a high AUC(0-infinity) of 187.6 microg ml(-1) h. Genotyping studies revealed that this subject was heterozygous for CYP2C9*3 and a new variant CYP2C9 allele. Of the other 17 subjects, 13 were *1/*1 carriers, three were *1/*3 carriers, and one was a *1/*2 carrier. Mean AUC(0-infinity) values (95% confidence intervals) of lornoxicam were 9.25 (6.55, 11.95) vs. 4.75 (3.55, 5.95) microg ml(-1) h in *1 heterozygotes vs.*1 homozygotes, and mean CL/F values were 14.8 (10.2, 19.4) vs. 32.9 (24.5, 41.3) ml min(-1), respectively (P < 0.05 for both AUC and CL/F). CONCLUSIONS: The results show that the pharmacokinetics of lornoxicam are dependent on CYP2C9 polymorphism. In particular, the presence of the CYP2C9*3 allele impairs the oral clearance of lornoxicam.     

Role of CYP2C9 and its variants (CYP2C9*3 and CYP2C9*13) in the metabolism of lornoxicam in humans.

CYP2C9 is an important member of the cytochrome P450 enzyme superfamily with some 12 CYP2C9 alleles (*1-*12) being previously reported. Recently, we identified a new CYP2C9 allele with a Leu90Pro mutation in a Chinese poor metabolizer of lornoxicam [Si D, Guo Y, Zhang Y, Yang L, Zhou H, and Zhong D (2004) Pharmacogenetics 14:465-469]. The new allele, designated CYP2C9*13, was found to occur in approximately 2% of the Chinese population. To examine enzymatic activity of the CYP2C9*13 allele, kinetic parameters for lornoxicam 5'-hydroxylation were determined in COS-7 cells transiently transfected with pcDNA3.1 plasmids carrying wild-type CYP2C9*1, variant CYP2C9*3, and CYP2C9*13 cDNA. The protein levels of cDNA-expressed CYP2C9*3 and *13 in postmitochondrial supernatant (S9) from transfected cells were lower than those from wild-type CYP2C9*1. Mean values of Km and Vmax for CYP2C9*1, *3, and *13 were 1.24, 1.61, and 2.79 microM and 0.83, 0.28, and 0.22 pmol/min/pmol, respectively. Intrinsic clearance values (Vmax/Km) for variant CYP2C9*3 and CYP2C9*13 on the basis of CYP2C9 protein levels were separately decreased to 28% and 12% compared with wild type. In a subsequent clinical study, the AUC of lornoxicam was increased by 1.9-fold and its oral clearance (CL/F) decreased by 44% in three CYP2C9*1/*13 subjects, compared with CYP2C9*1/*1 individuals. This suggests that the CYP2C9*13 allele is associated with decreased enzymatic activity both in vitro and in vivo.     

Chlorpropamide 2-hydroxylation is catalysed by CYP2C9 and CYP2C19 in vitro: chlorpropamide disposition is influenced by CYP2C9, but not by CYP2C19 genetic polymorphism

AIMS: We evaluated the involvement of cytochrome P450 (CYP) isoforms 2C9 and 2C19 in chlorpropamide 2-hydroxylation in vitro and in chlorpropamide disposition in vivo. METHODS: To identify CYP isoforms(s) that catalyse 2-hydroxylation of chlorpropamide, the incubation studies were conducted using human liver microsomes and recombinant CYP isoforms. To evaluate whether genetic polymorphisms of CYP2C9 and/or CYP2C19 influence the disposition of chlorpropamide, a single oral dose of 250 mg chlorpropamide was administered to 21 healthy subjects pregenotyped for CYP2C9 and CYP2C19. RESULTS: In human liver microsomal incubation studies, the formation of 2-hydroxychlorpropamide (2-OH-chlorpropamide), a major chlorpropamide metabolite in human, has been best described by a one-enzyme model with estimated K(m) and V(max) of 121.7 +/- 19.9 microm and 16.1 +/- 5.0 pmol min(-1) mg(-1) protein, respectively. In incubation studies using human recombinant CYP isoforms, however, 2-OH-chlorpropamide was formed by both CYP2C9 and CYP2C19 with similar intrinsic clearances (CYP2C9 vs. CYP2C19: 0.26 vs. 0.22 microl min(-1) nmol(-1) protein). Formation of 2-OH-chlorpropamide in human liver microsomes was significantly inhibited by sulfaphenazole, but not by S-mephenytoin, ketoconazole, quinidine, or furafylline. In in vivo clinical trials, eight subjects with the CYP2C9*1/*3 genotype exhibited significantly lower nonrenal clearance [*1/*3 vs.*1/*1: 1.8 +/- 0.2 vs. 2.4 +/- 0.1 ml h(-1) kg(-1), P < 0.05; 95% confidence interval (CI) on the difference 0.2, 1.0] and higher metabolic ratios (of chlorpropamide/2-OH-chlorpropamide in urine: *1/*3 vs.*1/*1: 1.01 +/- 0.19 vs. 0.56 +/- 0.08, P < 0.05; 95% CI on the difference - 0.9, - 0.1) than did 13 subjects with CYP2C9*1/*1 genotype. In contrast, no differences in chlorpropamide pharmacokinetics were observed for subjects with the CYP2C19 extensive metabolizer vs. poor metabolizer genotypes. CONCLUSIONS: These results suggest that chlorpropamide disposition is principally determined by CYP2C9 activity in vivo, although both CYP2C9 and CYP2C19 have a catalysing activity of chlorpropamide 2-hydroxylation pathway.     

Effects of St John's wort and CYP2C9 genotype on the pharmacokinetics and pharmacodynamics of gliclazide

BACKGROUND AND PURPOSE: Patients commonly take complementary medicines in conjunction with conventional drugs without clear evidence of safety or the risk of herb-drug interactions. The aim of this study was to assess potential pharmacokinetic (PK) and pharmacodynamic (PD) interactions between St John's wort and gliclazide in healthy subjects with different cytochrome P450 2C9 (CYP2C9) genotypes. EXPERIMENTAL APPROACH: A crossover controlled study was conducted in 21 healthy subjects. Each received gliclazide (80 mg) either alone or during 15 days treatment with St John's wort. The area under the plasma concentration-time curve (AUC(0-infinity)), apparent clearance (CL/F) and elimination half-life (t 1/2) of gliclazide and incremental changes in glucose and insulin AUC(0-4) were compared. CYP2C9*2 and CYP2C9*3 alleles were identified using PCR followed by restriction enzyme digestion analysis. KEY RESULTS: St John's wort significantly altered gliclazide pharmacokinetics in all except for four healthy subjects. The mean ratio and 90% confidence interval (CI) of gliclazide AUC(0-infinity) and CL/F were 0.67 (0.55-0.81) and 1.50 (1.24-1.81), respectively, after St John's wort treatment. St John's wort decreased gliclazide t (1/2), with mean ratio and 90% CI of 0.85 (0.74-0.93). There were no significant changes in glucose or insulin AUC(0-4) after St John's wort treatment and no significant differences according to CYP2C9 genotype. CONCLUSIONS AND IMPLICATIONS: Treatment with St John's wort significantly increases the apparent clearance of gliclazide which is independent of CYP2C9 genotype. People with diabetes receiving this combination should be closely monitored to evaluate possible signs of reduced efficacy.     

Herbal medicine yin zhi huang induces CYP3A4-mediated sulfoxidation and CYP2C19-dependent hydroxylation of omeprazole

Aim： To explore the potential interactions between Y/n Zhi Huang （YZH） and omeprazole, a substrate of CYP3A4 and CYP2C19. Methods： Eighteen healthy volunteers, including 6 CYP2C19＊ 1/＊ 1, 6 CYP2C19＊1/＊2 or ＊3 and 6 CYP2C19＊2/ ＊2 were enrolled in a 2-phase, randomized, crossover clinical trial. In each phase, the volunteers received either placebo or 10 mL YZH oral liquid, 3 times daily for 14 d. Then all the patients took a 20 mg omeprazole capsule orally. Blood samples were collected up to 12 h after omeprazole administration. Plasma concentrations of omeprazole and its metabolites were quantified by HPLC with UV detection. Results： After 14 d of treatment of YZH, plasma omeprazole significantly decreased and those of omeprazole sulfone and 5-hydroxyomeprazole significantly increased. The ratios of the area under the plasma concentration-time curves from time 0 to infinity （AUC（0-∞） of omeprazole to 5-hydroxyomprazole and those of omeprazole to omeprazole sulfone decreased by 64.80%＋ 12.51% （P= 0.001） and 63.31%＋ 18.45 % （P=0.004） in CYP2C 19＊ 1/＊ 1, 57.98 %± 14.80% （P=0.002） and 54.87%±18.42% （P=0.003） in CYP2C19＊1/＊2 or ＊3, and 37.74%±16.07% （P= 0.004） and 45.16%±15.54% （P=0.003） in CYP2C19＊2/＊2, respectively. The decrease of the AUC（0-∞） ratio of omeprazole to 5-hydroxyomprazole in CYP2C19＊ 1/＊ 1 and CYP2C19＊1/＊2 or ＊3 was greater than those in CYP2C19＊2/＊2 （P=0.047 and P=0.009）. Conclusion： YZH induces both CYP3A4-catalyzed sulfoxidation and CYP2C19-dependent hydroxylation of omeprazole leading to decreases in plasma omeprazole concentrations.     

Influence of age and cytochrome P450 2C9 genotype on the steady-state disposition of diclofenac and celecoxib

OBJECTIVE: To analyse the influence of age and cytochrome P450 (CYP) 2C9 genotype on the steady-state disposition of the standard NSAID diclofenac and the new COX-2 selective inhibitor celecoxib, both of which are metabolised by the polymorphically expressed CYP2C9. DESIGN: Double-blind randomised crossover study under steady-state conditions. SUBJECTS: 12 young (age 32 +/- 5 years, bodyweight 71 +/- 12kg; mean +/- SD) and 12 elderly (68 +/- 2 years, 82 +/- 15kg) healthy, drug-free, nonsmoking Caucasians of both sexes. METHODS: All subjects received oral celecoxib (200mg twice daily) and diclofenac (75mg twice daily) for 15 days separated by a drug-free interval of at least 3 weeks. Following the last morning dose, multiple blood samples were taken for 25 hours. Concentrations of celecoxib and diclofenac were measured by specific and sensitive high performance liquid chromatography. Identification of CYP2C9 genotype was performed by genomic DNA sequencing. Pharmacokinetic parameters for total and unbound drugs were individually analysed by noncompartmental techniques. RESULTS: For diclofenac, area under the concentration-time curve over the dosage interval (AUC(tau)) was larger in young subjects (3.2 +/- 1.0 mg * h/L) than in older individuals (2.4 +/- 0.4 mg * h/L; p < 0.05). As the terminal half-life (t((1/2)Z)) was very similar in both groups (3.9 +/- 4.4 vs 3.5 +/- 3.3 hours), either less complete absorption in the elderly or their higher bodyweight could account for the difference. For celecoxib, AUC(tau) (5.8 +/- 1.7 vs 5.6 +/- 2.3 mg * h/L) and t((1/2)z) (11.8 +/- 8.7 vs 11.2 +/- 2.9 hours) were almost identical in young and older subjects. Plasma protein binding of both NSAIDs was unaffected by age, and apparent oral clearances for unbound drugs were not different between the two groups of healthy subjects. When considering the genotype of all individuals (CYP2C9*1/*1, n = 10; CYP2C9*1/*2, n = 6; CYP2C9*2/*2, n = 2; CYP2C9*1/*3, n = 4; CYP2C9*3/*3, n = 1), no association with any pharmacokinetic parameter of either drug was apparent. Moreover, there was no significant correlation between the AUC values of celecoxib and diclofenac. CONCLUSIONS: Age and CYP2C9 genotype do not significantly affect the steady-state disposition of celecoxib and diclofenac. This would indicate that both drugs need no dosage reduction in the elderly (at least up to 75 years) and that, besides CYP2C9, additional CYP species contribute to the elimination of both agents.     

The impact of CYP2C8 polymorphism and grapefruit juice on the pharmacokinetics of repaglinide

AIMS: The primary aim of the study was to investigate the possible effect of the CYP2C8*3 allele and of grapefruit juice on the pharmacokinetics of repaglinide. Furthermore, the impact of a single dose of grapefruit juice on the pharmacokinetics of repaglinide in relation to dose. METHODS: Thirty-six healthy male subjects, genotyped for CYP2C8*3 (11 genotyped as CYP2C8*1/*3, one as CYP2C8*3/*3 and 24 as CYP2C8*1/*1), participated in a randomized, cross-over trial. In the two phases, the subjects drank 300 mL water or 300 mL grapefruit juice, in randomized order, 2 h before administration of a single dose of either 0.25 mg or 2 mg repaglinide. RESULTS: Neither the mean AUC(0-infinity) (geometric mean ratio: 1.01; 95% CI: 0.93-1.1, P = 0.88) nor the mean C(max) (geometric mean ratio: 1.05; 95% CI: 0.94-1.2, P = 0.35) of repaglinide were statistically significantly different in the group carrying the CYP2C8*3 mutant allele compared with wild-types. Grapefruit juice caused a 19% decrease in the geometric mean ratio of the 3-hydroxyquinidine to quinidine ratio (difference: 0.81; 95% CI: 0.75-0.87, P < 0.0001), which was used as an index of CYP3A4 activity, and an increase in the mean AUC(0-infinity) of repaglinide (geometric mean ratio: 1.13; 95% CI: 1.04-1.2, P = 0.0048), but had no statistically significant effect on the t(1/2). There was no statistically significant difference in blood glucose concentration in subjects who had or had not ingested grapefruit juice. The effect was more pronounced at the low dose of repaglinide (0.25 mg) than at the therapeutic dose of 2 mg. CONCLUSIONS: The pharmacokinetics of repaglinide in subjects carrying the CYP2C8*3 mutant allele did not differ significantly from those in the wild-types. Grapefruit juice increased the bioavailability of repaglinide, suggesting significant intestinal elimination of the drug which was assumed to be primarily mediated by CYP3A4 in the gut.     

Determinants of steady-state torasemide pharmacokinetics: impact of pharmacogenetic factors, gender and angiotensin II receptor blockers

BACKGROUND: Torasemide is frequently used for the treatment of hypertension and heart failure. However, the determinants of torasemide pharmacokinetics in patients during steady-state conditions are largely unknown. We therefore explored the impact of genetic polymorphisms of cytochrome P450 (CYP) 2C9 (CYP2C9) and organic anion transporting polypeptide (OATP) 1B1 (SLCO1B1), gender, and the effects of losartan and irbesartan comedication on the interindividual variability of steady-state pharmacokinetics of torasemide. PATIENTS AND METHODS: Twenty-four patients receiving stable medication with torasemide 10 mg once daily and with an indication for additional angiotensin II receptor blocker (ARB) treatment to control hypertension or to treat heart failure were selected. Blood samples were taken before torasemide administration and 0.5, 1, 2, 4, 8, 12 and 24 hours after administration. After this first study period, patients received either irbesartan 150 mg (five female and seven male patients aged 69+/-8 years) or losartan 100 mg (two female and ten male patients aged 61+/-8 years) once daily. After 3 days of ARB medication, eight blood samples were again collected at the timepoints indicated above. The patients' long-term medications, which did not include known CYP2C9 inhibitors, were maintained at a constant dose during the study. All patients were genotyped for CYP2C9 (*1/*1 [n=15]; *1/*2 [n = 4]; *1/*3 [n=5]) as well as for SLCO1B1 (c.521TT [n=13]; c.521TC [n=11]). RESULTS: Factorial ANOVA revealed an independent impact of the CYP2C9 genotype (dose-normalized area under the plasma concentration-time curve during the 24-hour dosing interval at steady state [AUC(24,ss)/D]: *1/*1 375.5+/-151.4 microg x h/L/mg vs *1/*3 548.5+/-271.6 microg x h/L/mg, p=0.001), the SLCO1B1 genotype (AUC(24,ss)/D: TT 352.3+/-114 microg x h/L/mg vs TC 487.6+/-218.4 microg x h/L/mg, p<0.05) and gender (AUC(24,ss)/D: males 359.5+/-72.2 microg x h/L/mg vs females 547.3+/-284 microg x h/L/mg, p<0.01) on disposition of torasemide. Coadministration of irbesartan caused a 13% increase in the AUC(24,ss)/D of torasemide (p=0.002), whereas losartan had no effect. CONCLUSION: This study shows that the CYP2C9*3 and SLCO1B1 c.521TC genotype and female gender are significant and independent predictors of the pharmacokinetics of torasemide. Coadministration of irbesartan yields moderate but significant increases in the torasemide plasma concentration and elimination half-life.     

Benzbromarone pharmacokinetics and pharmacodynamics in different cytochrome P450 2C9 genotypes

Benzbromarone is a uricosuric drug and has been shown to be metabolized predominantly by cytochrome P450(CYP)2C9 in vitro findings. This study aims to investigate the influence of the CYP2C9 genotype on plasma levels of benzbromarone and 6-hydroxybenzbromarone, as well as uric acid lowering effects. A single oral dose pharmacokinetic and pharmacodynamic trial of benzbromarone (100 mg) was performed in 20 healthy volunteers, which included 15 with CYP2C9*1/*1, 4 with CYP2C9*1/*3, and 1 with CYP2C9*3/*3. The oral clearance of benzbromarone in the CYP2C9*1/*1 genotype and CYP2C9*1/*3 genotype was 58.8±25.2 L/hr/kg (mean±SD) and 51.3±7.9 L/hr/kg, respectively, whereas 8.58 L/hr/kg in the CYP2C9*3/*3 genotype. The metabolic ratio (6-hydroxybenzbromarone/benzbromarone) in urine was 38.6±10.7 in the CYP2C9*1/*1 genotype, 35.4±12.4 in the CYP2C9*1/*3 genotype and 12.9 in the CYP2C9*3/*3 genotype. Although benzbromarone significantly increased the urinary excretion and reduced the plasma concentration of uric acid, there were no significant differences in its effects for different CYP2C9 genotypes. These results suggest a critical role for CYP2C9 in the metabolism of benzbromarone in humans and a possible risk of toxicity in the CYP2C9*3 homozygote by lowering clearance of the drug. Further studies are required to assess the clinical impact of CYP2C9 on the metabolism of benzbromarone.     

Effects of the CYP2C9*1/*13 genotype on the pharmacokinetics of lornoxicam

Lornoxicam is extensively metabolized by CYP2C9, and a CYP2C9*13 is one of the principal variant alleles in East Asian populations. The aim of this study was to evaluate the effects of CYP2C9*1/*13 on the pharmacokinetic parameters of lornoxicam in healthy individuals. A single oral dose of 8 mg lornoxicam was given to 22 Korean volunteers with different CYP2C9 genotypes (8, 8 and 6 carriers of CYP2C9*1/*1, *1/*3 and *1/*13 genotypes, respectively). Lornoxicam and 5'-hydroxylornoxicam levels were analysed using HPLC-UV in plasma samples collected up to 24 hr after taking the drug. In individuals with CYP2C9*1/*13, lornoxicam had a higher C(max) (p < 0.001), a longer half-life (p < 0.001), a lower oral clearance (p < 0.001) and a higher area under the plasma concentration-time curve from zero to infinity (AUC(inf) ) than in CYP2C9*1/*1 individuals (p < 0.001). The C(max) and AUC(inf) of 5'-hydroxylornoxicam were lower in CYP2C9*1/*13 individuals than in CYP2C9*1/*1 individuals, but the half-life of 5'-hydroxylornoxicam did not differ between the two groups. The half-life, oral clearance and AUC(inf) of lornoxicam were similar in individuals with CYP2C9*1/*13 and those with CYP2C9*1/*3. The C(max) , half-life and AUC(inf) of 5'-hydroxylornoxicam were also similar in both groups, although C(max) was higher in CYP2C9*1/*13 individuals (p < 0.01). A CYP2C9*1/*13 genotype markedly reduced the conversion of lornoxicam to 5'-hydroxylornoxicam, to a similar extent as that observed with the CYP2C9*1/*3 genotype.