Genetic polymorphisms and the impact of a higher clopidogrel dose regimen on active metabolite exposure and antiplatelet response in healthy subjects

A double-blind crossover study was conducted in four CYP2C19 genotype-defined metabolizer groups to assess whether increase in clopidogrel dosing can overcome reduced pharmacodynamic response in CYP2C19 poor metabolizers (PMs). Ten healthy subjects in each of four metabolizer groups were randomized to a clopidogrel regimen of a 300-mg loading dose (LD) and a 75-mg/day maintenance dose (MD) for 4 days followed by 600-mg LD and 150 mg/day MD, or vice versa. The exposure levels of clopidogrel's active metabolite H4 (clopi-H4) in PMs were 71% lower on the 75-mg/day regimen and 64% lower on the 150-mg/day regimen than the corresponding exposure levels in extensive metabolizers (EMs). In PMs, the maximal platelet aggregation (MPA) induced by adenosine diphosphate (ADP) 5 μmol/l was 10.5% lower on the 75-mg/day regimen and 7.9% lower on the 150-mg/day regimen than the corresponding values in EMs. PMs who were on the clopidogrel regimen of 600-mg LD/150 mg/day MD showed clopi-H4 exposure and MPA levels similar to those in EMs who were on the regimen of 300-mg LD/75 mg/day MD. In a pooled analysis evaluating CYP1A2, CYP2B6, CYP2C9, CYP2C19, CYP3A5, CYP2D6, ABCB1, and P2RY12 polymorphisms (N = 396 healthy subjects), only CYP2C19 had a significant impact on antiplatelet response. In healthy CYP2C19 PMs, a clopidogrel regimen of 600-mg LD/150 mg/day MD largely overcomes diminished clopi-H4 exposure and antiplatelet response, as assessed by MPA levels.     

The effect of CYP2C19 polymorphism on the pharmacokinetics and pharmacodynamics of clopidogrel: a possible mechanism for clopidogrel resistance

We evaluated the effect of the CYP2C19 genotype on the pharmacokinetics and pharmacodynamcis of clopidogrel. Twenty-four subjects were divided into three groups on the basis of their CYP2C19 genotype: homozygous extensive metabolizers (homoEMs, n = 8), heterozygous EMs (heteroEMs, n = 8), and poor metabolizers (PMs, n = 8). After a single 300-mg loading dose of clopidogrel on day 1, followed by a 75-mg daily maintenance dose from days 2 to 7, we measured the plasma levels of clopidogrel and assessed the antiplatelet effect as pharmacodynamics. The mean clopidogrel area under the curve (AUC) for PMs was 1.8- and 2.9-fold higher than that for heteroEMs and homoEMs, respectively (P = 0.013). The mean peak plasma concentration in PMs was 1.8- and 4.7-fold higher than that of heteroEMs and homoEMs, respectively (P = 0.008). PMs exhibited a significantly lower antiplatelet effect than heteroEMs or homoEMs (P < 0.001). From these findings it is clear that the CYP2C19 genotype affects the plasma levels of clopidogrel and modulates the antiplatelet effect of clopidogrel.     

Potent mechanism-based inhibition of human CYP2B6 by clopidogrel and ticlopidine

The thienopyridine derivatives ticlopidine and clopidogrel are inhibitors of ADP-induced platelet aggregation. Pharmacological activity of these prodrugs depends on cytochrome P450 (P450)-dependent oxidation to the active antithrombotic agent. In this study, we investigated the interaction potential of clopidogrel and ticlopidine by using human liver microsomes and recombinantly expressed P450 isoforms. Both clopidogrel and ticlopidine inhibited CYP2B6 with highest potency and CYP2C19 with lower potency. Clopidogrel also inhibited CYP2C9, and ticlopidine also inhibited CYP1A2, with lower potency. Inhibition of CYP2B6 was time- and concentration-dependent, and as shown by dialysis experiments, it was irreversible and dependent on NADPH, suggesting a mechanism-based mode of action. Inactivation was of nonpseudo-firstorder type with maximal rates of inactivation (K(inact)) for clopidogrel and ticlopidine in microsomes (recombinant CYP2B6) of 0.35 (1.5 min(-1)) and 0.5 min(-1) (0.8 min(-1)), respectively, and half-maximal inactivator concentrations (KI) were 0.5 microM (1.1 microM) for clopidogrel and 0.2 microM (0.8 microM) for ticlopidine. Inhibition was attenuated by the presence of alternative active site ligands but not by nucleophilic trapping agents or reactive oxygen scavengers, further supporting mechanism-based action. A chemical mechanism is discussed based on the known metabolic activation of clopidogrel and on the finding that hemoprotein integrity of recombinant CYP2B6 was not affected by irreversible inhibition. These results suggest the possibility of drug interactions between thienopyridine derivates and drug substrates of CYP2B6 and CYP2C19.     

Common polymorphisms of CYP2C19 and CYP2C9 affect the pharmacokinetic and pharmacodynamic response to clopidogrel but not prasugrel

BACKGROUND: Thienopyridines are metabolized to active metabolites that irreversibly inhibit the platelet P2Y(12) adenosine diphosphate receptor. The pharmacodynamic response to clopidogrel is more variable than the response to prasugrel, but the reasons for variation in response to clopidogrel are not well characterized. OBJECTIVE: To determine the relationship between genetic variation in cytochrome P450 (CYP) isoenzymes and the pharmacokinetic/pharmacodynamic response to prasugrel and clopidogrel. METHODS: Genotyping was performed for CYP1A2, CYP2B6, CYP2C19, CYP2C9, CYP3A4 and CYP3A5 on samples from healthy subjects participating in studies evaluating pharmacokinetic and pharmacodynamic responses to prasugrel (60 mg, n = 71) or clopidogrel (300 mg, n = 74). RESULTS: In subjects receiving clopidogrel, the presence of the CYP2C19*2 loss of function variant was significantly associated with lower exposure to clopidogrel active metabolite, as measured by the area under the concentration curve (AUC(0-24); P = 0.004) and maximal plasma concentration (C(max); P = 0.020), lower inhibition of platelet aggregation at 4 h (P = 0.003) and poor-responder status (P = 0.030). Similarly, CYP2C9 loss of function variants were significantly associated with lower AUC(0-24) (P = 0.043), lower C(max) (P = 0.006), lower IPA (P = 0.046) and poor-responder status (P = 0.024). For prasugrel, there was no relationship observed between CYP2C19 or CYP2C9 loss of function genotypes and exposure to the active metabolite of prasugrel or pharmacodynamic response. CONCLUSIONS: The common loss of function polymorphisms of CYP2C19 and CYP2C9 are associated with decreased exposure to the active metabolite of clopidogrel but not prasugrel. Decreased exposure to its active metabolite is associated with a diminished pharmacodynamic response to clopidogrel.     

冠脉支架术后氯吡格雷和噻氯匹定应用的临床观察

目的 探讨冠脉支架术后应用氯吡格雷和噻氯匹定加阿司匹林的抗血小板聚集作用及其安全性。方法对158例冠脉内支架随机分别应用氯吡格雷75mg/d和阿司匹林300mg/d加低分子肝紊0．5mL／d(CA组n=32)、噻氯匹定500mg/d和阿司匹林300mg/d加低令子肝素0．5mL／d(TA组n=126)，测定血栓与止血功能及观察心脏事件、药物的副作用。结果 两组患者抗血小板聚集作用的效果和心脏事件发生率相似。药物副作用：噻氯匹定中性粒细胞减少(1．5％比0)、腹泻(5．6％比3．1％)、皮疹(8．6％比3．1％)均高于氯吡格雷(P(O．05)。结论 氯吡格雷在支架置入后是一种有效的抗血小板聚集药物，其副作用少，且优于噻氯匹定。     

Pharmacokinetic basis of the antiplatelet action of prasugrel

Prasugrel is the most recent development of thienopyridine-type antiplatelet drugs. Like the earlier-generation thienopyridines, i.e. ticlopidine and clopidogrel, prasugrel is also an inactive prodrug that requires metabolic processing in vivo to generate the active antiplatelet metabolite. The efficacy of this bioactivation is the key determinant for the pharmacodynamic potency of the compound, i.e. the irreversible blockade of the platelet P2Y12-ADP receptor. Prasugrel is rapidly absorbed from the gut. After oral administration of standard-loading doses of 60 mg, maximum plasma levels of the active metabolite are achieved within 1 h, effective, maximum inhibition of platelet aggregation at 1-2 h. Bioconversion of prasugrel into the active metabolite requires two metabolic steps that occur in sequence. The first is the generation of a thiolactone-intermediate, mainly by carboxyesterases-2 in the intestine, the second the cytochrome (CYP)-dependent conversion of the thiolactone into the active metabolite. This second step involves several cytochromes, most notably CYP3A4, CYP2C19, CYP2B6, and CYP2C9. The enzymatic generation of the active metabolite of prasugrel is much more effective than that of clopidogrel where only about 5% of oral clopidogrel is transformed into the active compound by two-step CYP-dependent procedures. About 70% of prasugrel metabolites are excreted in the urine and 30% in the feces. The molar potency of the respective active metabolites of prasugrel and clopidogrel is identical. Thus, the more rapid onset, higher potency and lower interindividual variability of antiplatelet effects of prasugrel as compared to clopidogrel in vivo are entirely because of its more efficient pharmacokinetics.     

Effects of CYP2C19 Genetic Polymorphisms on the Pharmacokinetic and Pharmacodynamic Properties of Clopidogrel and Its Active Metabolite in Healthy Chinese Subjects

Purpose

Some studies in the white population have shown that carriers of at least 1 loss-of-function allele in the gene that encodes the cytochrome P-450 2C19 isozyme (CYP2C19) have lower levels of the clopidogrel active metabolite (CAM) and a reduced antiplatelet effect of clopidogrel. However, data are limited regarding the association between CYP2C19 genetic variants and exposure to CAM and on the pharmacodynamic properties of CAM in the Chinese population. Data from the white population cannot be extrapolated to the Chinese population because of the marked interethnic differences in CYP2C19 variants. This study was aimed to investigate the influence of CYP2C19 genetic polymorphisms on the pharmacokinetic properties of CAM and the antiplatelet effect of clopidogrel in healthy Chinese volunteers, and to provide evidence for the role of a CYP2C19 genotyping test in predicting the antiplatelet effect of clopidogrel in the Chinese population.

Dissecting the activation of thienopyridines by cytochromes P450 using a pharmacodynamic assay in vitro

The thienopyridine antiplatelet drugs, such as ticlopidine, clopidogrel, and prasugrel, require activation by cytochromes P450 in vivo to effectively block platelet aggregation. The study of the metabolic activation of these compounds has been hampered by the lability and reactivity of the ring-opened active metabolite (AM) and by the numerous metabolites that can be formed in such a transformation. We have developed a novel method whereby platelets are incubated with the cytochrome P450 and the thienopyridine of interest for various amounts of time, and the effects on ADP-driven platelet aggregation are directly examined. In this way, the platelet is used as a biosensor for detection of the AM. Using this method, cytochromes P450 capable of converting clopidogrel, prasugrel, and 2-oxo-clopidogrel to metabolites that inhibit ADP-induced platelet aggregation were identified as well as which cytochromes P450 were capable of catalyzing partial reactions (e.g., conversion of 2-oxo-clopidogrel to the AM). These studies show that, in vitro, CYP3A4/5, 2C19, and 2B6 are individually capable of converting clopidogrel and prasugrel to the AM and that the cytochrome P450 preference for these two thienopyridines is very similar.     

Aggrenox: a fixed-dose combination of aspirin and dipyridamole

OBJECTIVE: To describe the pharmacology, pharmacokinetics, efficacy, and safety of a fixed-dose combination of aspirin and extended-release (ER) dipyridamole indicated for the secondary prevention of stroke. DATA SOURCES: Published articles and abstracts were identified from a MEDLINE search (1966-December 1999) using the search terms dipyridamole, aspirin, antiplatelet, antiaggregation, and stroke prevention. Pertinent articles written in English were considered for review. Additional articles were identified from the references of retrieved literature. STUDY SELECTION AND DATA EXTRACTION: Studies including a combination of aspirin/dipyridamole in human subjects were evaluated. Emphasis was placed on randomized, controlled trials. DATA SYNTHESIS: Aspirin is a platelet inhibitor that works by inhibiting platelet cyclooxygenase, which reduces the production of thromboxane A2. Dipyridamole is a platelet inhibitor that is thought to work in part by inhibiting platelet cyclic-3',5'-adenosine monophosphate and cyclic-3',5'-guanosine monophosphate phosphodiesterase. The active metabolite of aspirin, salicylic acid, is highly bound to plasma protein and has a plasma half-life of two to three hours. Dipyridamole is also highly bound to plasma proteins, and the ER formulation has a plasma half-life of 13 hours. The first European Stroke Prevention Study (ESPS-1) found the combination of aspirin/dipyridamole to be superior to placebo in the prevention of stroke and transient ischemic attack (TIA). The ESPS-1, however, did not include an aspirin-only treatment arm. Therefore, it was unclear whether the combination of aspirin/dipyridamole was superior to aspirin alone. As a result, a second trial was conducted that included treatment arms of aspirin alone, ER dipyridamole alone, combination therapy, and placebo. The combination of aspirin 25 mg plus ER dipyridamole 200 mg twice daily was shown in the ESPS-2 to be significantly better than either agent given individually in preventing stroke and TIAs (p < 0.001). CONCLUSIONS: The American College of Chest Physicians (ACCP) recommends aspirin 50-325 mg/d to be the initial antiplatelet of choice for the prevention of atherothrombotic cerebral ischemic events. However, with the favorable results of the ESPS-2, it may be appropriate to substitute aspirin/ER dipyridamole for aspirin alone as the drug of choice. This combination appears to have a favorable adverse effect profile. The relative effectiveness of aspirin/ER dipyridamole compared with clopidogrel and ticlopidine has yet to be determined. If alternative antiplatelet therapy is needed, the ACCP recommends clopidogrel rather than ticlopidine because of its lower incidence of adverse effects. The ACCP further states that the combination of aspirin plus dipyridamole may be more effective than clopidogrel; these agents have a similarly favorable adverse effect profile.     

脑梗死患者抗血小板药物的精准策略选择

抗血小板治疗是脑梗死全程管理的重要手段之一,然而临床上存在抗血小板药物个体反应差异且其与患者预后密切相关,因此精准选择抗血小板药物具有重要意义。血小板功能检测及基因检测是抗血小板药物精准治疗的核心环节。对于存在高危缺血风险或预后较差、有高出血风险的患者,可考虑行基因检测和（或）血小板功能检测。阿司匹林和氯吡格雷仍是目前最常用的抗血小板药物,其他抗血小板药物的有效性及安全性有待进一步验证。对于阿司匹林抵抗人群,不推荐增加阿司匹林剂量,可考虑换用其他抗血小板药物。基于CYP2C19基因型进行氯吡格雷剂量调整的策略仍有待研究,而携带CYP2C19失功能等位基因的患者,建议换用其他抗血小板药物。     

血栓弹力图评价经皮冠脉介入治疗患者服用抗血小板药物效果的研究

目的评价采用血栓弹力图观察经皮冠脉介入治疗（PCI）患者服用抗血小板药物后血小板抑制效果。方法选择住院的135例冠心病患者,其中120例接受PCI治疗并联合服用阿司匹林与氯吡格雷的患者作为联合用药组,15例未接受PCI治疗的患者（单独用药组）分别单独服用阿司匹林（阿司匹林组,8例）或氯吡格雷（氯吡格雷组,7例）。采用血栓弹力图检测花生四烯酸（AA）和磷酸腺苷（ADP）途径诱导的血小板抑制率,并比较两组抗血小板治疗的效果。结果阿司匹林组AA途径诱导的血小板抑制率为（61．66±21．44）％,高于氯吡格雷组ADP途径诱导的血小板抑制率[（55．23±13．44）％],但差异无统计学意义（P〉0．05）;联合用药组AA和ADP途径诱导的血小板抑制率分别为（65．52±24．61）％和（58．67±22．75）％,高于阿司匹林组AA途径和氯吡格雷组ADP途径,但差异无统计学意义（P均〉0．05）;联合用药组抗血小板治疗的疗效（良好率）均优于单独应用阿司匹林或氯吡格雷组（40．00％郴12．50％,26．67％ vs 0,P均〈0．01）。结论阿司匹林与氯吡格雷均能起到很好的抗血小板作用,但氯吡格雷稍差,联合服用阿司匹林和氯吡格雷能起到更强的抗血小板作用。血栓弹力图是评价血小板抑制率的有效工具,可根据AA／ADP抑制率的情况发现对阿司匹林和／或氯吡格雷抵抗的患者,进而调整用药方案。     

Differential effects of esomeprazole on the antiplatelet activity of clopidogrel in healthy individuals and patients after coronary stent implantation

Clopidogrel plus aspirin is a standard antiplatelet aggregation regimen in cardiovascular diseases, especially after implantation of a coronary stent. Interaction between clopidogrel and proton pump inhibitors theoretically reduces clopidogrel's antiaggregation effect, but the evidence is controversial. A total of 30 healthy subjects and 74 patients with a coronary stent were given a 300 mg loading dose of aspirin and 300 mg clopidogrel and then 100 mg aspirin/75 mg clopidogrel daily for 14 days. Subgroups were concomitantly treated or not treated with esomeprazole (20 mg/day). Clopidogrel significantly reduced adenosine diphosphate-induced platelet aggregation in healthy and stent-implanted subjects on days 7 and 14. Healthy subjects receiving esomeprazole showed a significantly higher platelet aggregation rate than those not receiving esomeprazole, but esomeprazole had no effect in patients with a stent. Aspirin plus clopidogrel did not result in significant gastrointestinal complications. These differential effects of esomeprazole on the antiplatelet activity of clopidogrel in healthy individuals and patients after coronary stent implantation merit further investigation.     

Ex vivo--in vitro interaction between aspirin, clopidogrel, and the glycoprotein IIb/IIIa inhibitors abciximab and SR121566A

OBJECTIVES: To assess the interaction between aspirin and clopidogrel in healthy male volunteers and the interaction of the glycoprotein IIb/IIIa (GPIIb/IIIa) inhibitors abciximab and SR121566A with blood from those pretreated subjects (ex vivo-in vitro). METHODS: Aspirin (300 mg/day), clopidogrel (75 mg/day), or the combination of both drugs were administered orally for 8 days. Group 1 (n = 5) started with aspirin and group 2 (n = 5) with clopidogrel. From day 4 to day 8, subjects of both groups received the combined treatment. Blood from these subjects was spiked with abciximab (0.5 and 1.5 microg x mL(-1)) and SR121566A (31 and 62 ng x mL(-1)). RESULTS: In vivo, average bleeding times were 6.8 minutes at baseline, 20.3 minutes for clopidogrel alone (P < .01), 10.9 minutes for aspirin alone (difference not significant), and 24.0 minutes (P < .01) for the combined treatment. Fibrinogen binding to the platelet GPIIb/IIIa receptor was reduced for aspirin to 69% (difference not significant), to 63% for clopidogrel (difference not significant), and to 63% for the clopidogrel plus aspirin combination (P < .01). CD62 expression as a marker of platelet granular secretion was reduced to 66% by clopidogrel (P < .01) and to 41% by the combination of clopidogrel and aspirin; aspirin alone had no effect. In vitro, with pretreatment with aspirin and clopidogrel, inhibitory effects of the GPIIb/IIIa inhibitors on fibrinogen binding were additive to changes observed with aspirin or clopidogrel alone. No effect on CD62 expression was observed with either GPIIb/IIIa inhibitor. Aspirin and clopidogrel reinforced effects of the GPIIb/IIIa inhibitors on adenosine diphosphate (5 micromol/L)-induced aggregation in an additive manner, a supra-additive effect was observed with collagen (2 microg x mL(-1))-induced aggregation. CONCLUSION: The augmentation of the antiaggregatory effects of GPIIb/IIIa inhibitors by aspirin and clopidogrel and the lack of antisecretory effects of GPIIb/IIIa inhibitors may favor their combination with clopidogrel.     

血栓弹力图测定老年急性冠脉综合征患者氯吡格雷抵抗的临床观察

【目的】通过血栓弹力图（TEG）分析仪检测血小板聚集率,观察接受标准双联抗血小板治疗的住院老年急性冠脉综合征（ACS）患者的氯吡格雷抵抗发生率及可能的影响因素。【方法】选取109例老年（年龄≥60岁）ACS患者,在常规服用阿司匹林100mg／d基础上,口服氯吡格雷75mg／d,5d以后采血,通过TEG方法测定患者服用氯吡格雷和阿司匹林的血小板聚集率。以二磷酸腺苷诱导的血小板聚集率≥70％为氯吡格雷抵抗,花生四烯酸诱导的血小板聚集率〉50％为阿司匹林抵抗。【结果】氯吡格雷抵抗发生率为31．2％（34例）,有10．1％（11例）发生阿司匹林和氯吡格雷双抵抗。氯吡格雷抵抗组与非抵抗组间阿司匹林抵抗的发生率有非常显著的统计学意义（P〈0．01）。两组患者在年龄、高血压、糖尿病、应用药物等方面差异无统计学意义（P〉0．05）;但氯吡格雷抵抗组中无吸烟史的患者更多,差异具有统计学意义（P=0．045）;此外还观察到女性（P=0．052）患者有容易发生氯吡格雷抵抗的趋势。【结论】接受标准抗血小板治疗的老年ACS患者中,31．2％存在氯吡格雷抵抗现象。这一现象不受年龄、合并疾病、服用药物等影响,而阿司匹林抵抗或从未吸烟的患者更易发生氯吡格雷抵抗。     

Long-term care after percutaneous coronary intervention: focus on the role of antiplatelet therapy

Arterial wall injury caused by percutaneous coronary intervention (PCI) triggers transient platelet activation and mural thrombosis; these effects are superimposed on the preexisting platelet hyperreactivity associated with underlying atherothrombosis. Platelet activation has been implicated in the major complications of PCI: acute and subacute thrombosis and restenosis. Antithrombotic and anticoagulant therapy minimizes thrombotic complications after PCI. Aspirin plus a thienopyridine (ticlopidine or clopidogrel) is more effective than aspirin plus heparin and extended warfarin therapy in preventing periprocedural ischemic events and subsequent stent thrombosis and results in less major and minor bleeding. Dual antiplatelet therapy with aspirin and clopidogrel (the preferred thienopyridine because of its superior hematologic safety) is recommended for at least 4 weeks to prevent subacute stent thrombosis with bare-metal stents and 3 to 6 months to prevent late-stent thrombosis with drug-eluting stents. Coronary atherothrombosis is a diffuse vascular disease, and reduction of the risk of future ischemic events requires strategies that extend beyond the focal treatment of stenotic lesions. Optimal long-term care after PCI requires aggressive systemic pharmacotherapy (antiplatelet agents, statins, beta-blockers, and angiotensin-converting enzyme Inhibitors) in conjunction with therapeutic lifestyle changes (smoking cessation, weight reduction, dietary measures, and exercise). In this context, dual antiplatelet therapy (aspirin plus clopidogrel) is recommended for at least 12 months after PCI for prophylaxis of future atherothrombotic events.     

Influence of CYP450 Enzymes,CES1, PON1, ABCB1, and P2RY12 Polymorphisms on Clopidogrel Response in Patients Subjected to a Percutaneous Neurointervention

PurposeClopidogrel is a thienopyridine prodrug that inhibits platelet aggregation. It is prescribed to prevent atherothrombotic and thromboembolic events in patients receiving a stent implant in carotid, vertebral, or cranial arteries. The influence of cytochrome P-450 (CYP) 2C19 on the response to clopidogrel has been widely studied; however, the effect of other genes involved in clopidogrel absorption and metabolism has not been established in this cohort of patients.MethodsThis observational retrospective study assessed the antiplatelet response and the prevalence of hemorrhagic or ischemic events after percutaneous neurointervention in clopidogrel-treated patients, related to 35 polymorphisms in the genes encoding the clopidogrel-metabolizing enzymes (CYP2C19, CYP1A2, CYP2B6, CYP2C9, CYP2C9, CYP3A4, CYP3A5, carboxylesterase-1 [CES1], and paraoxonase-1 [PON1]), P-glycoprotein transporter (ABCB1), and platelet receptor P2Y₁₂. Polymorphisms were analyzed by quantitative real-time polymerase chain reaction and matrix-assisted laser desorption/ionization–time-of-flight mass spectrometry. Antiplatelet response was documented with the VerifyNow system (Accriva, San Diego, California).FindingsWe confirmed that CYP2C19 is the most important enzyme involved in clopidogrel response. The carriage of the CYP2C19*2 allele was strongly associated with hyporesponse to clopidogrel, while the CYP2C19*17 allele was a protective factor for the development of ischemic events (odds ratio = 0.149; P = 0.002) but a risk factor for bleeding (odds ratio = 3.60; P = 0.038). Patients carrying ABCB1 mutated alleles showed lower aggregation values, suggesting that clopidogrel absorption is influenced by P-glycoprotein. In fact, the percentage of responders was significantly higher in the group carrying the mutated haplotype compared to the wild type (80.8% vs 43.3%; P = 0.009). Patients with the CES1 G143E C/T genotype showed a considerably lower, aggregation value versus wild-type patients, although the difference was not significant likely due to the small sample size (59.0 [21.2] vs 165.2 [86.0] PRU; P = 0.084), which suggests an increased active metabolite formation. No relationship was found between polymorphisms in other CYP genes, PON1, or P2RY12 and response to clopidogrel in patients subjected to neurointervention procedures.ImplicationsTherapeutic guidelines recommend that CYP2C19 intermediate and poor metabolizers with acute coronary syndromes undergoing percutaneous coronary intervention receive an alternative antiplatelet therapy; however, genotype-guided therapy is not a standard recommendation for neurovascular conditions. This is the first study to carry out a joint analysis of CYP2C19 and other genes involved in clopidogrel treatment in patients receiving percutaneous neurointervention. Our findings support routine genotyping in clopidogrel-treated patients. Moreover, we encourage considering an alternative antiplatelet therapy in CYP2C19 intermediate, poor and ultrarapid metabolizers. Additionally, ABCB1 polymorphisms could be considered for a better pharmacogenetic approach.     

不同抗血小板方案对急性冠状动脉综合征经皮冠状动脉介入术后患者的疗效与安全性研究

目的探讨不同强化抗血小板治疗方案对急性冠状动脉综合征（ACS）经皮冠状动脉介入术（PCI）后患者氯吡格雷抵抗（CR）发生率及超敏C-反应蛋白（hs-CRP）的影响。方法将125例确诊为ACS急诊行PCI术后的患者,随机分为三组,A组（n=42）：口服阿司匹林100 mg Qd＋氯吡格雷75 mg Qd;B组（n=42）：口服阿司匹林100 mg Qd＋氯吡格雷75 mg Bid;C组（n=41）：口服阿司匹林100 mg Qd＋氯吡格雷75 mg Qd＋西洛他唑50 mg Bid。利用全血电阻抗法检测治疗前、治疗第7天的血小板聚集率,酶联免疫吸附法测定PCI前、PCI术后24 h、PCI术后第7天的hs-CRP,计算并比较CR的发生率,观察住院期间主要不良心脏事件（MACE）发生率、出血并发症。结果 B组与C组的CR发生率无显著差异（16.7%vs.14.6%）,两组均明显低于A组（35.7%）（P〈0.05）;B组和C组PCI术后24 h、PCI术后第7天的hs-CRP水平无显著差异[（12.5±7.4）mg/L vs.（12.8±7.1）mg/L,（9.2±6.8）mg/L vs.（8.5±6.3）mg/L],两组均明显低于A组[（16.7±6.3）mg/L,（11.8±5.4）mg/L,P〈0.05];B组和C组MACE发生率明显低于A组[（2.4%,2.4%）vs.16.7%]（P〈0.05）;C组出血率明显高于A组和B组[14.6%vs（.2.4%,2.4%）]（P〈0.05）。结论两种强化抗血小板治疗方案均明显降低ACS急诊PCI术后患者CR发生率和hs-CRP水平,标准双联抗血小板联合西洛他唑方案的出血发生率明显低于阿司匹林联合双倍氯吡格雷方案。     

Comparison of collagen versus adenosine diphosphate in detecting antiplatelet effect in patients with coronary artery disease

Widely varying methods of assessing platelet aggregation have resulted in the absence of an established standard approach to assess the effects of antiplatelet drugs. The objective of this study was to compare the roles of collagen and adenosine diphosphate (ADP) in the assessment of effects of aspirin or clopidogrel on platelet aggregation. Sixty patients with documented coronary artery disease were assigned to receive aspirin alone (ASA 100 mg/d) (n = 30) or aspirin-plus-clopidogrel (ASA 100 mg/d + C 75 mg/d) (n = 30). Platelet aggregation assessment by the use of whole blood aggregation tests with collagen or ADP was performed in these patients and 30 age- and gender-matched normal volunteers. When compared with the control group, therapy with ASA or ASA + C resulted in significant inhibition of collagen-induced platelet aggregation (P < 0.001 for each), but there was no statistically significant difference in the results between the ASA and ASA + C groups. When platelet aggregation was induced by ADP, the combined therapy with aspirin and clopidogrel decreased platelet aggregation significantly when compared with aspirin alone (P < 0.001), and no significant difference in the results between the ASA and normal groups was observed. In conclusion, collagen may prove useful to study the effect of aspirin and ADP may be appropriate for assessing the inhibitory effect of clopidogrel.     

Effect of clopidogrel and ticlopidine on cytochrome P450 2B6 activity as measured by bupropion hydroxylation

OBJECTIVE: Our objective was to study the effect of the antiplatelet agents clopidogrel and ticlopidine on bupropion (INN, amfebutamone) hydroxylation, a probe reaction for cytochrome P450 (CYP) 2B6 activity. METHODS: Twelve healthy male volunteers took a single 150-mg oral dose of bupropion either alone or after pretreatment with 75 mg clopidogrel once daily or 250 mg ticlopidine twice daily for 4 days. On day 4, a single 150-mg oral dose of bupropion was administered. Plasma concentrations of bupropion and its CYP2B6-catalyzed metabolite, hydroxybupropion, were measured for up to 72 hours. RESULTS: The mean area under the plasma concentration-time curve (AUC) of hydroxybupropion calculated from time 0 to infinity was reduced by 52% ( P = .001; 95% confidence interval [CI], 39% to 66%) by clopidogrel and by 84% ( P < .0001; 95% CI, 73% to 94%) by ticlopidine. Clopidogrel reduced the AUC ratio of hydroxybupropion over bupropion by 68% ( P = .002; 95% CI, 58% to 77%) and ticlopidine by 90% ( P = .001; 95% CI, 85% to 96%). The AUC of bupropion was increased by 60% ( P = .02; 95% CI, 21% to 98%) and by 85% ( P < .0001; 95% CI, 48% to 85%) with clopidogrel and ticlopidine, respectively. CONCLUSIONS: Both clopidogrel and ticlopidine significantly inhibited the CYP2B6-catalyzed bupropion hydroxylation. Patients receiving either clopidogrel or ticlopidine are likely to require dose adjustments when treated with drugs primarily metabolized by CYP2B6.