CYP2D6基因多态性与阿立哌唑及其代谢物血药浓度的相关性研究

目的 研究CYP2D6基因多态性与精神分裂症患者阿立哌唑及其活性代谢物脱氢阿立哌唑血药浓度的相关性。方法 纳入200例经阿立哌唑治疗的精神分裂症患者,采集清晨服药前空腹血,采用LC-MS/MS法测定阿立哌唑及其代谢物脱氢阿立哌唑稳态谷浓度。通过Axiom基因芯片分析技术检测CYP2D6(*2、*5、*10、*41)4个SNP位点的基因型,比较不同基因型患者阿立哌唑及其代谢物的浓度剂量比（C/D）及代谢物与阿立哌唑血药浓度比值（CDARI/CARI）的差异。结果 200例精神分裂症患者CYP2D6正常代谢型与中代谢型患者脱氢阿立哌唑C/D值差异存在统计学意义（P <0.05）;CYP2D6正常代谢型与慢代谢型患者脱氢阿立哌唑C/D值差异存在高度统计学意义（P <0.01）;CYP2D6正常代谢型与慢代谢型患者阿立哌唑及其代谢物总浓度C/D值差异存在统计学意义（P <0.05）。结论 CYP2D6基因多态性可影响阿立哌唑体内药动学过程,建议临床根据患者CYP2D6基因型制定个体化治疗方案。     

CYP2D6 CYP2C19*2基因多态性与利培酮治疗精神分裂症临床效应的相关研究

目的探讨CYP2D6和CYP2C19基因多态性与利培酮治疗精神分裂症临床效应个体差异之间的相关性。方法应用聚合酶链反应(PCR)与DNA测序相结合的方法检测精神分裂症患者CYP2D6和CYP2C19基因多态性。应用高效液相色谱分别测定利培酮、9-羟利培酮的血药浓度,以治疗前后阳性和阴性症状量表(PANSS)评分减分率评价药物临床疗效,比较不同基因型之间血药浓度和药物临床疗效的差异。结果55例单用利培酮治疗的精神分裂症患者,CYP2D6(C100T)不同基因型之间利培酮血药浓度分布差异有统计学意义(P<0.05),但该位点与该药的临床效应之间没有相关性(P>0.05)。CYP2C19*2(G681A)基因多态性与利培酮在体内代谢以及该药临床效应之间差异无统计学意义(P>0.05)。结论CYP2D6(C100T)对利培酮血药浓度有影响,但与利培酮的临床效应个体差异间无相关性。CYP2C19*2(G681A)可能不是引起利培酮代谢以及临床效应个体差异的主要因素。     

CYP2D6*10和CYP2C19*2基因型多态性与接受他莫昔芬治疗乳腺癌患者生存率的相关性研究

目的:研究CYP2D6*10和CYP2C19*2基因型多态性与接受他莫昔芬(tamoxifen,TAM)治疗乳腺癌患者生存率的相关性研究.方法:选择2009至2004年本院甲乳外科和肿瘤内科收治的171名术后服用TAM治疗的雌激素阳性乳腺癌患者,调查TAM使用情况和生存状态等相关资料;收集相关的石蜡组织切片用于DNA提取;用PCR技术检测CYP2D6*10和CYP2C19*2基因型多态性;查明CYP2D6*10和CYP2C19*2基因型多态性与患者生存率的相关性.结果:本次研究中,CYP2D6Wt/Wt、CYP2D6Wt/*10 和CYP2D6*10/*10基因型的总生存率(overall survival,OS)类似,差异无统计学意义(P＞0.05).CYP2C19*2/*2基因型的5年OS明显优于CYP2C19 Wt/Wt,差异具有统计学意义(P＜0.05);CYP2C19*2/*2基因型的10年OS明显优于CYP2C19 Wt/Wt和CYP2C19 Wt/*2,差异具有统计学意义(P＜0.05);但是CYP2C19Wt/Wt与CYP2C19 Wt/*2的5、10年OS差异无统计学意义(P＞0.05).结论:研究结果显示,CYP2D6*10基因型多态性与服用TAM治疗乳腺癌患者的生存率之间不存在相关性;CYP2C19*2基因型多态性与接受TAM治疗乳腺癌患者的生存率之间存在相关性,CYP2C19*2/*2接受TAM治疗乳腺癌患者的生存率最高,CYP2C19 Wt/*2生存率较高,CYP2C19 Wt/Wt较低.     

中国人CYP3A5和CYP2D6基因多态性与他莫昔芬及其活性代谢物血药浓度的相关性

目的：研究中国汉族人群CYP3A5和CYP2D6基因多态性与乳腺癌患者体内他莫昔芬及其活性代谢物4-羟基他莫昔芬血药浓度的相关性。方法：30例乳腺癌患者,应用PCR方法检测其CYP3A5和CYP2D6基因型,应用LC—MS／MS方法测定患者体内他莫昔芬及其活性代谢物4-羟基他莫昔芬的含量,对试验数据进行统计分析。结果：CYP3A5基因型与乳腺癌患者体内他莫昔芬的浓度差异有统计学意义,比较发现＊1／＊1和＊1／＊3组的他莫昔芬的浓度值明显低于＊3／＊3组（P〈0．01）。CYP2D6基因型与其活性代谢物4-羟基他莫昔芬的浓度差异有统计学意义;＊1／＊1和＊1／＊10两组4-羟基他莫昔芬的浓度值都明显高于＊10／＊10组（P〈0．01）,但＊1／＊1组和＊1／＊10组之间4-羟基他莫昔芬的浓度值差异无统计学意义（P〉0．05）。结论：乳腺癌患者的CYP3A5和CYP2D6基因型影响他莫昔芬的体内代谢,相关基因型的测定可以为他莫昔芬个体化合理用药提供依据。     

CYP2C9、CYP2C19、CYP3A4基因多态性对磺脲类降糖药代谢的影响

磺脲类口服降糖药在人体内主要经过肝脏代谢。肝脏中的细胞色素氧化酶P450是一种重要的药物代谢酶系统,在人群中存在基因多态性,导致药物疗效和不良反应在个体间存在着较大的差异。本文将对CYP450中的几种重要的代谢酶亚型CYP2C9、CYP2C19、CYP3A4的基本结构、基因多态性、种族差异及其对磺脲类降糖药代谢的影响作一综述。     

CYP2C19基因多态性对精神分裂症患者丙戊酸血药浓度的影响

目的 研究CYP2C19基因多态性与精神分裂症患者心境稳定剂丙戊酸血药浓度的关系。方法 选择奥氮平治疗且服用丙戊酸钠作为心境稳定剂的精神分裂症患者160例,采集血液,测定CYP2C19基因型以及丙戊酸血药浓度,比较各个基因型血药浓度的差异。结果 *2/*2型(122.06±41.30)mg·L^-1和*2/*3型(132.34±51.34)mg·L^-1患者丙戊酸血药浓度明显高于野生*1/*1型(79.41±25.14)mg·L^-1(P<0.05或P<0.01);*1/*1、*1/*2和*1/*3型之间、*2/*2和*2/*3型之间血药浓度无统计学差异;PM型血药浓度(122.13±42.85)mg·L^-1与EM型(80.59±48.60)mg·L^-1比较,显著升高(P<0.05)。 结论 *2/*2和*2/*3型CYP2C19患者,其血液丙戊酸浓度较高,该类患者服用丙戊酸作为精神分裂症心境稳定剂时,宜适当降低用药剂量。     

黄芪颗粒和黄芪注射液对CYP1A2、CYP2D、CYP2C亚酶活性影响的实验研究

目的通过体内和体外实验研究黄芪颗粒和黄芪注射液对CYP1A2、CYP2D、CYP2C亚酶的活性影响。方法建立体外"cocktail"反应体系,利用LC/MS/MS法测定酶代谢产物,计算黄芪颗粒和黄芪注射液对CYP1A2、CYP2D6、CYP2C9和CYP2C19亚酶活性的影响;大鼠随机分为对照组和实验组,不同浓度黄芪颗粒和黄芪注射液连续灌胃10 d,制备肝微粒体并进行"cocktail"反应,评价两种药物体内对大鼠CYP1A2、CYP2D1、CYP2C6和CYP2C11亚酶活性影响。结果在体外"cocktail"实验中,黄芪颗粒和黄芪注射液明显地抑制了CYP2D6、CYP2C19和CYP1A2亚酶活性,而二者对于CYP2C9亚酶活性无影响。在大鼠灌胃给药实验中,黄芪颗粒在剂量32、160和800 mg.kg-1.d-1提高CYP1A2亚酶活性2.13、3.23和2.20倍,黄芪注射液在剂量0.16、0.8、4 g.kg-1.d-1提高CYP1A2亚酶活性1.65、2.26和2.89倍,而二者均未诱导CYP2D1、CYP2C6和CYP2C11亚酶活性增加。结论黄芪颗粒和黄芪注射液对CYP2D6、CYP2C19活性有抑制作用,对大鼠CYP1A2活性有诱导作用。     

CYP2D6基因多态性及其临床意义

CYP2D6是CYP酶系中重要的一种氧化代谢酶,参与多种药物的代谢.CYP2D6具有基因多态性,使药物代谢在不同种族之间,甚至在同种族不同人群中产生较大的差异,从而影响药物的疗效.因此,深入了解CYP2D6基因的多态性以及对药物代谢的影响,对指导临床合理用药和调整用药方案具有重大意义.     

抑郁症患者CYP2D6基因多态性与文拉法辛代谢的相关性研究

目的：探讨汉族抑郁症患者CYP2D6基因多态性对文拉法辛体内代谢的影响。方法：以79名抑郁症住院患者为研究对象,采用液相色谱-质谱/质谱联用技术测定患者体内文拉法辛及去甲文拉法辛血药浓度,采用sanger测序对患者CYP2D6*4基因（rs3892097）、CYP2D6*5基因（基因缺失）、CYP2D6*10基因（rs1065852）和CYP2D6*14基因（rs5030865）进行SNPs分型。结果：（1）CYP2D6*4、CYP2D6*5、CYP2D6*14 3个基因的突变检出率为0%。根据CYP2D6*10（rs1065852）基因分型结果将患者分为3组：CC组（15例,19.0%）、CT组（25例,31.6%）和TT组（39例,49.4%）,其中T等位基因突变频率为65.2%;（2）3组间C_VEN、C_ODV、剂量校正前后C_VEN+C_ODV浓度差异无统计学意义;CC、CT和TT组C_ODV/C_VEN分别为6.0、4.0和3.0,其中CC与TT组间差异有高度统计意义（P<0.01）,CC与CT组间差异有统计意义（P<0.05）。（3）不同性别组间C_ODV和剂量校正前后的C_VEN+C_ODV差异有统计意义：女性组C_ODV（368.6 ng·mL^-1）高出男性组（267.0 ng·mL^-1）38.1%;女性组C_VEN+C_ODV（499.3 ng·mL^-1）高出男性组（406.7 ng·mL^-1）22.8%;女性组剂量校正后C_VEN+C_ODV（2.5 ng·mL^-1·mg^-1）高出男性组（2.1 ng·mL^-1·mg^-1）19.0%。结论：研究未发现不同CYP2D6基因型组间药物浓度差异有统计意义,但不同基因型组间文拉法辛代谢率（C_ODV/C_VEN）差异有显著性。文拉法辛体内代谢存在性别差异,但临床疗效是否有差异有待进一步研究;相对于男性患者,女性患者暴露于更高的药物浓度之下,发生药物不良反应的风险更高,因此临床治疗女性患者时剂量调整需更加缓慢和谨慎。     

CYP2C19*1、*2基因多态性与氯吡格雷抵抗相关性的系统评价

目的:系统评价CYP2C19*1、*2基因型心血管疾病患者对服用氯吡格雷临床疗效的影响。方法:电子检索PubMed、EBSCO、EMbase、Cochrane library、CNKI、万方中文期刊数据库及维普期刊数据库(VIP),再辅以手工检索,查找有关携带CYP2C19*1、*2基因的心血管疾病患者与氯吡格雷疗效关系的临床对照试验和观察性研究,检索时限为建库至2016年12月。由2名研究者根据纳入与排除标准独立筛选文献、质量评价及数据提取,采用RevMan 5.0软件进行Meta分析。结果:纳入5篇研究,共4544例心血管疾病患者。Meta分析结果显示:心血管疾病患者服用氯吡格雷后,CYP2C19*1和CYP2C19*2基因携带患者植入支架后血栓再形成发生率有显著差异[P=0.000 2,RR=2.46,95%CI(1.54,3.92)],其CYP2C19*2基因型携带者较CYP2C19*1型可明显增加血栓形成,但2组在心血管事件发生率上差异不显著(P>0.05)。结论:在服用氯吡格雷的心血管患者中,CYP2C19*2基因型较CYP2C19*1基因型更易发生支架后血栓,但心血管时间发生率未见明显差异,鉴于CYP2C19*2基因型携带患者发生植入支架后血栓再形成风险增加,建议在拟行PCI手术并使用氯吡格雷的患者应先测定CYP2C19*2基因型,再考虑是否应用氯吡格雷抗血小板治疗。     

Dose-dependent inhibition of CYP1A2, CYP2C19 and CYP2D6 by citalopram,fluoxetine, fluvoxamine and paroxetine

Objectives: The purpose of this pharmacokinetic study was to investigate the dose-dependent inhibition of model substrates for CYP2D6, CYP2C19 and CYP1A2 by four marketed selective serotonin reuptake inhibitors (SSRIs): citalopram, fluoxetine, fluvoxamine and paroxetine. Methods: The study was carried out as an in vivo single-dose study including 24 young, healthy men. All volunteers had been identified as sparteine- and mephenytoin-extensive metabolisers. The volunteers received in randomised order, at weekly intervals, increasing single oral doses of one of the four SSRIs, followed 3 h later by sparteine (CYP2D6), mephenytoin (CYP2C19) and caffeine (CYP1A2) tests. Fluoxetine was given at 3-week intervals because of the long half-life of fluoxetine and its metabolite norfluoxetine. Citalopram, fluoxetine and paroxetine were given in doses of 10, 20, 40 and 80 mg and fluvoxamine was given in doses of 25, 50, 100 and 200 mg. Results: With increasing doses, there was a statistically significant increase in the sparteine metabolic ratio (MR) (P < 0.01, Page’s test for trend) for all four SSRIs. The increase was modest after intake of citalopram and fluvoxamine, while the increase was more pronounced after fluoxetine intake, although no volunteers changed phenotype from extensive metabolisers to poor metabolisers. Three of the six volunteers changed phenotype from extensive metabolisers to poor metabolisers after intake of 40 or 80 mg paroxetine. There was a statistically significant increase in the mephenytoin S/R ratio (P < 0.01, Page’s test for trend) with increasing doses of fluoxetine and fluvoxamine, but not after citalopram and paroxetine. However, no volunteers changed phenotype from extensive to poor metabolisers of S-mephenytoin. After intake of fluvoxamine, the urinary excretion of the metabolites related to N3 demethylation of caffeine were below the limit of quantification, whereas there were no significant changes in the urinary caffeine metabolic ratios after intake of the other three SSRIs. Conclusion: This investigation confirms that paroxetine and fluoxetine are potent inhibitors of CYP2D6, that fluvoxamine and fluoxetine are moderate inhibitors of CYP2C19 and that fluvoxamine is a potent inhibitor of CYP1A2 in humans in vivo. The clinical prediction of interaction from single-dose experiments may have to take the degree of accumulation during steady-state after multiple doses into account. Received: 11 December 1995/Accepted in revised form: 29 February 1996     

Impact of CYP2D6, CYP3A5, CYP2C9 and CYP2C19 polymorphisms on tamoxifen pharmacokinetics in Asian breast cancer patients

AIM

To investigate the impact of genetic polymorphisms in CYP2D6, CYP3A5, CYP2C9 and CYP2C19 on the pharmacokinetics of tamoxifen and its metabolites in Asian breast cancer patients.

METHODS

A total of 165 Asian breast cancer patients receiving 20 mg tamoxifen daily and 228 healthy Asian subjects (Chinese, Malay and Indian; n = 76 each) were recruited. The steady-state plasma concentrations of tamoxifen and its metabolites were quantified using high-performance liquid chromatography. The CYP2D6 polymorphisms were genotyped using the INFINITI™ CYP450 2D6I assay, while the polymorphisms in CYP3A5, CYP2C9 and CYP2C19 were determined via direct sequencing.

RESULTS

The polymorphisms, CYP2D6*5 and *10, were significantly associated with lower endoxifen and higher N-desmethyltamoxifen (NDM) concentrations. Patients who were *1/*1 carriers exhibited 2.4- to 2.6-fold higher endoxifen concentrations and 1.9- to 2.1-fold lower NDM concentrations than either *10/*10 or *5/*10 carriers (P < 0.001). Similarly, the endoxifen concentrations were found to be 1.8- to 2.6-times higher in *1/*5 or *1/*10 carriers compared with *10/*10 and *5/*10 carriers (P≤ 0.001). Similar relationships were observed between the CYP2D6 polymorphisms and metabolic ratios of tamoxifen and its metabolites. No significant associations were observed with regards to the polymorphisms in CYP3A5, CYP2C9 and CYP2C19.

CONCLUSIONS

The present study in Asian breast cancer patients showed that CYP2D6*5/*10 and *10/*10 genotypes are associated with significantly lower concentrations of the active metabolite of tamoxifen, endoxifen. Identifying such patients before the start of treatment may be useful in optimizing therapy with tamoxifen. The role of CYP3A5, CYP2C9 and CYP2C19 seem to be minor.     

CYP2D6 and CYP2C19 genotypes in an elderly Swedish population

Objective: Eighty-three healthy elderly Swedish subjects (age 87 ± 4 years, mean ± SD, range 80–98 years) were genotyped with respect to the two genetic polymorphisms of oxidative drug metabolism, CYP2D6 and CYP2C19, using allele-specific polymerase chain reaction (PCR). A control population consisted of 248 younger unrelated healthy volunteers (age 31 ± 9 years, range 19–63 years) for CYP2D6, and 162 (age 30 ± 8 years, range 19–55 years) for CYP2C19. Results: No significant differences were found between the control groups and the elderly subjects with respect to the frequencies of the defect alleles CYP2D6*3, CYP2D6*4, CYP2C19*2 and CYP2C19*3. Neither were there any differences in the genotype frequencies, or the predicted phenotype frequencies. The study indicates that the CYP2D6 and CYP2C19 genotypes play no major role in the probability of reaching high age. Conclusion: No genetically determined differences in the pharmacokinetics of drugs metabolized by these two polymorphic enzymes are to be expected in the oldest age groups compared with younger adults. Received: 10 March 1998 / Accepted: 1 May 1998     

Polymorphism of CYP2D6, CYP2C19, CYP2C9 and CYP2C8 in the Faroese population

Objective The purpose of the study was to study the distribution of poor and extensive metabolizers of CYP2C19 and CYP2D6 and to genotype for CYP2C8 and CYP2C9 among 312 randomly selected Faroese.Methods and results The participants were phenotyped for CYP2D6 with the use of sparteine. The distribution of the sparteine metabolic ratio (sparteine/didehydrosparteines) was bimodal, and 14.5% (n=44; 95% CI: 10.7–18.9%) of the subjects were phenotyped as poor metabolizers. The frequency of poor metabolizers was higher (P=0.0002; ² test) among the Faroese than in other European populations (7.4%). Genotype analyses for the CYP2D6*3, *4, *6 and *9 alleles were performed using real-time polymerase chain reaction (PCR) (TaqMan, Foster City, CA, USA), and we found 14.6% (n = 45) (95% CI: 10.8–19.0%) with deficient CYP2D6 genes (*3/*4, *4/*4, *4/*6, *6/*6) in the Faroese population. The subjects were phenotyped for CYP2C19 with the use of mephenytoin and 10 subjects, i.e., 3.2% (95% CI: 1.6–5.9%) were phenotyped as poor metabolizers. Genotype analysis for the CYP2C19*2 and *3 alleles was performed by means of PCR analysis, and 2.9% (n=9) (95% CI: 1.3–5.4%) of the Faroese were found to have a deficient CYP2C19 gene all explained by the CYP2C19*2/*2 genotype. The allele frequencies of the CYP2C9*2 and CYP2C9*3 alleles were 8.8% (95% CI: 6.7–11.4%) and 5.3% (95% CI: 3.7–7.4%), respectively, while the CYP2C8*3 allele frequency was 6.9% (95% CI: 5.0–9.2%). Real-time PCR (TaqMan) was used for both CYP2C9 and CYP2C8 genotype analyses.Conclusion The frequency of CYP2D6 poor metabolizers is twofold higher among the Faroese population than other Caucasians, while the frequencies of Faroese subjects with decreased CYP2C19, CYP2C8 and CYP2C9 enzyme activity are the same as seen in other Caucasian populations. A possible consequence might be a higher incidence of side effects among Faroese patients taking pharmaceuticals that are CYP2D6 substrates.     

The impact of the CYP2D6 and CYP2C19 genotypes on venlafaxine pharmacokinetics in a Japanese population

Objective: The cytochrome P ₄₅₀ isozymes CYP2D6 and CYP2C19 exhibit genetic polymorphism in human, including a marked interethnic difference. As the functional status of the isozymes CYP2D6 and CYP2C19 have an impact on the pharmacokinetics of some antidepressants, we investigated whether the disposition of venlafaxine was affected by the CYP2D6 and CYP2C19 genotypes. Methods: Twenty-eight adult Japanese men in good health participated in this study. Genomic DNA was isolated from peripheral lymphocytes, and the CYP2D6 genotype was determined using polymerase chain reaction–restriction fragment length polymorphism (PCR-RFLP) analysis and XbaI-RFLP analysis. Subjects were categorized into the following four groups: group 1 CYP2D6*10/*10; group 2 CYP2D6*1/*10 and *2/*10; group 3 CYP2D6*1/*1, *1/*2 and *2/*2; and group 4 the other genotypes. Two defective CYP2C19 alleles (CYP2C19*2 and CYP2C19*3) were identified by means of PCR-RFLP analysis. Venlafaxine was administered orally following an overnight fast. Plasma concentrations of venlafaxine and O-desmethylvenlafaxine were monitored using high-performance liquid chromatography up to 24 h. Results: The peak plasma concentration and values of area under the concentration–time curve up to 24 h for venlafaxine were 298% and 453% higher for group 1 than group 3, and 91% and 120% higher for group 2 than for group 3, respectively. The homozygote for two defective alleles of CYP2C19 showed a higher concentration of venlafaxine within group 1 and group 2. Conclusion: The CYP2D6*10 allele and two CYP2C19 defective alleles, common in an Asian population, are the most likely genetic factors to use in determining interindividual differences in the pharmacokinetics of venlafaxine, although the results with respect to CYP2C19 are preliminary because of the few subjects used. Received: 6 July 1999 / Accepted in revised form 11 January 2000     

CYP2D6 and CYP2C19 genotypes of patients with terodiline cardiotoxicity identified through the yellow card system

AIMS: Terodiline has concentration dependent QT prolonging effects and thus the potential for cardiotoxicity. Pharmacogenetic variation in terodiline metabolism could be responsible for cardiotoxicity. We sought to determine whether CYP2D6 (debrisoquine hydroxylase) or CYP2C19 (S-mephenytoin hydroxylase) status is a risk factor for terodiline cardiotoxicity. METHODS: Using the UK Yellow Card scheme to identify patients, blood samples were obtained from eight patients who survived ventricular tachycardia or torsades de pointes suspected to be due to terodiline, for determination of CYP2D6 and CYP2C19 genotypes. Genotype prevalence was compared with that in published general population groups. RESULTS: One patient was a CYP2D6 poor metaboliser (CYP2D6*4 homozygous) and a second was heterozygous for CYP2D6*4, a slightly lower frequency for these genotypes compared with the general population (P = 0.31). In the case of CYP2C19, one patient was a poor metaboliser and four were heterozygous for the variant CYP2C19*2 allele, compared with general population frequencies of 2% and 23%, respectively (P = 0.035). CONCLUSIONS: These findings suggest that debrisoquine poor metaboliser status is not primarily responsible for terodiline cardiotoxicity. However, possession of the CYP2C19*2 allele appears to contribute to adverse cardiac reactions to terodiline. The present study demonstrates the feasibility of using spontaneous adverse drug reaction reporting schemes to determine the contribution of genotype for metabolizing enzymes to uncommon adverse drug reactions.     

Phenotypes and genotypes for CYP2D6 and CYP2C19 in a black Tanzanian population

AIMS: CYP2D6 and CYP2C19 are polymorphically expressed enzymes that show marked interindividual and interethnic variation. The aim of this study was to determine the frequency of the defective alleles in CYP2D6 and CYP2C19 in Africans and to test whether the genotype for CYP2C19 is better correlated with the proguanil/cylcoguanil ratio than the mephenytoin S/R ratio. METHODS: Two hundred and sixteen black Tanzanians were phenotyped for CYP2D6 with the use of sparteine, and for CYP2C19 with the use of mephenytoin and proguanil. Of these 196 subjects were also genotyped for CYP2D6 (including the CYP2D6*1, CYP2D6*3 and CYP2D6*4 alleles) and 195 were genotyped for CYP2C19 (including the CYP2C19*1, CYP2C19*2 and the CYP2C19*3 alleles). Furthermore 100 subjects were examined for the allele duplication in CYP2D6, leading to ultrarapid metabolism, with long PCR. RESULTS: The sparteine metabolic ratio (MR) was statistically significantly higher in the Tanzanian group of homozygous, extensive metabolizers compared to a historical control group of white Danish extensive metabolizers. Only one poor metabolizer for CYP2D6 (MR=124 and genotype CYP2D6*1/CYP2D6*4 ) was found. The gene frequencies were 0.96 for the CYP2D6*1 allele and 0.04 for the CYP2D6*4 allele. No CYP2D6*3 alleles were found. Nine subjects had an allele duplication in CYP2D6 (9%). For CYP2C19 there were seven subjects (3. 6%) who were phenotyped as poor metabolizers, but only three subjects (1.5%) had a genotype (CYP2C19*2/CYP2C19*2 ) indicative of poor metabolism. The gene frequencies were 0.90 for the CYP2C19*1 allele and 0.10 for the CYP2C19*2 allele. No CYP2C19*3 alleles were found. The mephenytoin S/R ratios were not bimodally distributed. CONCLUSIONS: Both the genotyping and phenotyping results show that there is a substantial difference between an African black population and a Caucasian population in the capacity to metabolize drugs via CYP2D6 and CYP2C19.     

Genetic polymorphism of debrisoquine (CYP2D6) and proguanil (CYP2C19) in South Pacific Polynesian populations

Objective: Genetic oxidation polymorphisms of debrisoquine (CYP2D6) and proguanil (CYP2C19) were studied in unrelated healthy South Pacific Polynesian volunteers recruited in the South Island of New Zealand. Methods: Phenotyping for CYP2D6 and CYP2C19 activities was determined using debrisoquine and proguanil, respectively, as probe drugs by measuring the urinary metabolic ratio of parent drug and its␣metabolite. Results: Of 100 Polynesian subjects phenotyped, the metabolic ratio of debrisoquine ranged from 0.01 to 9.94. Therefore, all South Pacific Polynesians were classified as extensive metabolizers of debrisoquine according to previously established criteria of the antimode. The prevalence of poor metabolizers of debrisoquine (CYP2D6) in this Polynesian population is 0% (95% confidence interval of 0–3.6%). Oxidation polymorphism of CYP2C19 using proguanil as a probe was also studied in 59 Polynesian volunteers. The frequency distribution of the proguanil/cycloguanil ratio was bimodal. The proguanil/cycloguanil ratios for these subjects ranged from 0.09 to 34.4. Using a recommended proguanil/cycloguanil ratio cut-off point of 10 established in Caucasian populations, eight Polynesian subjects were identified as poor metabolizers of proguanil (CYP2C19), which corresponds to a poor metabolizer phenotype frequency of 13.6% (a 95% confidence interval of 5.9–24.6%). Conclusion: The incidence of poor metabolizer phenotypes for debrisoquine (CYP2D6) in South Pacific Polynesians appears to lower than in Caucasian populations, while the prevalence of poor metabolizers for proguanil (CYP2C19) in this ethnic population is higher. The frequencies of the poor metabolizer phenotype for debrisoquine and also for proguanil in South Pacific Polynesians are similar to those reported in Asian populations. Received: 18 December 1997 / Accepted in revised form: 30 April 1998