In vivo effect of losartan on platelet aggregation in patients with hypertension

The angiotensin II receptor, losartan, has been found to inhibit platelet aggregability to some extent in in vitro experiments. There have been conflicting results about the in vivo effects of losartan. We sought to clarify the in vivo effect of losartan on platelet aggregation. Forty patients with grade I essential hypertension were treated with losartan for 3 weeks. Platelet aggregation tests with adenosine diphosphate (ADP) and ristocetin were analyzed and compared before and at the end of the study. Losartan effectively decreased systolic (SBP) and diastolic (DBP) blood pressure. Mean SBP before and after treatment was 159.6 ± 12.8 and 149.2 ± 17.3mmHg, respectively. Mean DBP decreased from 93.7 ± 8.2 to 87.7 ± 10.3mmHg after treatment. The results of the platelet aggregation tests with ADP and ristocetin were not significantly different when both rate and amplitude of maximal aggregation were included. Peak platelet aggregation with ADP regarding the lowest light transmission in the aggregometer was 59.8% ± 24.3% before and 58.3% ± 18.1% after the treatment. The same variables with ristocetin were 66.8% ± 21.6% and 60.8% ± 23.3%, respectively. In vivo effects of losartan on platelet aggregation with ADP and ristocetin were insignificant.     

Platelet function in uncomplicated insulin-dependent diabetic patients at rest and following exercise

There are conflicting reports of platelet function abnormalities in diabetic patients without vascular complications. We have studied in vitro platelet aggregation, using platelet rich plasma and whole blood techniques, in 18 patients with uncomplicated insulin-dependent diabetes and a matched group of 24 non-diabetic subjects. In addition we measured plasma beta-thromboglobulin levels in these groups, as an index of in vivo platelet activation, and compared the indices of in vitro and in vivo platelet function before and after maximal bicycle exercise. Before exercise plasma beta-thromboglobulin levels and platelet sensitivities to ADP, collagen or adrenaline, as assessed by both methods of platelet aggregation, were the same in diabetic and control subjects. Both groups showed similar increases in beta-thromboglobulin levels and in platelet sensitivity to all agonists in whole blood following exercise. Using platelet rich plasma there were no changes in platelet sensitivity in either group after exercise. In non-diabetic subjects, increases in noradrenaline levels after exercise correlated with increases in platelet sensitivity to adrenaline in whole blood. This was not observed in the diabetic group. Abnormalities of platelet function, using the techniques described here, are not present in diabetic patients who do not have clinical evidence of vascular disease.     

Platelet aggregation in whole blood from patients with Glanzmann's thrombasthenia

We examined platelet aggregation in platelet-rich plasma (PRP) and in whole blood from two patients with Glanzmann's thrombasthenia. In PRP, aggregation was measured by monitoring the changes in light absorbance that occurred in response to aggregating agents; to measure platelet aggregation in whole blood, we used a platelet counting technique. In PRP, the patients' platelets showed defective aggregation in response to ADP, adrenaline, arachidonic acid (AA), and collagen, but normal agglutination occurred in response to ristocetin. In whole blood, however, platelet aggregation in response to the aggregating agents appeared to be either very similar to that which occurred in blood from normal subjects or only slightly reduced. There was a reduced response to all concentrations of ADP and to low concentrations of collagen but a normal response to all concentrations of adrenaline, AA, and higher concentrations of collagen. Conversely, there seemed to be an increased agglutination response to ristocetin. The abnormality in our two patients with Glanzmann's thrombasthenia probably lies in the inability of their platelets to form large, macroscopic aggregates rather than in platelet aggregation per se.     

同型半胱氨酸作用于正常个体血小板凝聚反应的体外研究

目的　研究人体血清或血浆同型半胱氨酸 (HCY)的升高与血小板高凝状态的关系。方法　全血或浓缩血小板与不同浓度的 HCY于 37℃ (用于血小板凝聚检测 )或 2 2～ 2 5℃ [用于血小板纤维原结合及 P-选择素 (P- selectin)表达的检测 ]作用 15 min,后应用血小板凝聚仪和流式细胞仪分别检测 HCY对血小板活性的作用。结果　 HCY在浓度 30 μm ol/ L 时能增加一磷酸腺苷 (ADP)和胶原诱导的全血和浓缩血小板凝聚反应 [(3.0± 0 .8) Ω/ min vs(5 .0± 2 .0 ) Ω/ m in,P<0 .0 5 ,n=9和 (8.5± 1.5 ) Ω/ min vs(11± 2 .5 ) Ω/ min,P<0 .0 5 ,n=6 ],但在浓度 10 0 0μm ol/ L时却抑制 ADP和胶原诱导的全血和浓缩血小板凝聚反应 [(7.0± 4 .0 )Ω vs (3.6± 2 .6 )Ω和 (6 .8± 2 .2 )Ω vs (4.1± 3.3)Ω ,P<0 .0 5 ,n=9],血小板凝聚性的改变并不伴随血小板纤维原结合及 P- selectin表达的变化。结论　体外实验表明 HCY能协同促进已激活的血小板凝聚反应 ,可能是 HCY与体内血栓形成有关的机理之一     

国人血小板聚集曲线正常参数和图像分型的探讨

本文分析2120例用 ADP、肾上腺素、刺参酸性粘多糖、胶原和瑞斯托霉素诱导血小板聚集图像的正常参数,并按各种诱聚剂诱导的图像分为双相伴散聚型、双相不伴散聚型、初级聚集型和次级聚集型等,可作为推断血小板聚集功能的指标。     

Automated Plateletpheresis Does Not Cause an Increase in Platelet Activation in Volunteer Donors

Abstract: Activation of platelets during collection and storage has been implicated as a major cause of the platelet storage lesion. In this study, we investigated the effect of an automated plateletpheresis procedure on the in vivo platelet activation in 20 volunteer donors. Peripheral blood samples were collected immediately before and after plateletpheresis on the Haemonetics V50 Blood Cell Separator. Activation of platelets was determined by quantitating the amount of platelet P-selectin (CD62) expression using a whole blood method on flow cytometry. Adenosine diphosphate (ADP), collagen, and ristocetin induced platelet aggregations were also measured on a whole blood impedance aggregometer. Plateletpheresis caused a significant decrease in the CD62-positive platelet percentage and aggregation responses to 3 agonists. We concluded that the plateletpheresis procedure did not cause an increase in platelet activation in donors. Further studies are required to elucidate whether activated platelets are collected during the procedure or removed from the circulation of the donor and replaced by resting platelets, activated platelets bind to leukocytes or endothelial cells, and the plateletpheresis procedure is a powerful stimulus for platelet activation.—     

红葡萄酒及白藜三醇对血小板聚集的影响

观察红葡萄酒及其提取物白藜三醇对离体和在体条件下血小板聚集的影响 ,以探讨它们对心血管系统的保护作用机制。以高胆固醇饮食造成实验性高脂血症 ,以凝血酶、二磷酸腺苷和胶原为诱导剂 ,采用Born氏法测定血小板聚集率。结果发现 ,高脂饮食明显增加兔血浆胆固醇水平 ,并伴有血小板聚集的明显增强。同时给予红葡萄酒、去酒精红葡萄酒和白藜三醇可以消除高脂饮食对兔血小板聚集的增强作用。离体条件下白藜三醇明显抑制凝血酶、二磷酸腺苷及胶原诱导的健康人的血小板聚集。结果提示 ,红葡萄酒及白藜三醇均具有抑制血小板聚集的作用 ,此作用可能为白藜三醇抗动脉粥样硬化的机制之一。     

Platelet function tests using platelet aggregometry: need for repetition of the test for diagnosis of defective platelet function

Four hundred and ninety seven patients were referred to our center for platelet aggregation studies because of spontaneous mucocutaneous bleeds. All these patients had normal complete blood count, platelet count and peripheral smears except in ten patients of Bernard Soulier Syndrome where platelet count was marginally reduced in the presence of giant platelets. Two hundred and eighty patients were found to have normal platelet aggregation to ADP, collagen, ristocetin and arachidonic acid. Out of the remaining 217 patients, 62 patients were diagnosed to have Glanzmanns thrombasthenia, 10 Bernard Soulier Syndrome, 6 storage pool deficiencies, 7 cyclooxygenase deficiencies and 72 von Willebrand disease. In all the patients with GT and BSS, diagnosis was confirmed with flow cytometry using multiple monoclonal antibodies to GPIIb-IIIa and GPIb-IX. There were sixty patients where initial platelet aggregation studies showed reduced (<30%) aggregation to either ADP, collagen, ristocetin or arachidonic acid in its various combination, however in 12 such patients (20%) the platelet aggregation studies were normal on repetition. All our platelet aggregation studies were done only after assuring that the patient is not taking any medicine for at least 7 – 10 days which may affect the platelet function tests. The present study shows that single atypically abnormal platelet aggregation studies should always be repeated. Finally in 48/217 patients (22%) some aggregation abnormality to one or more of the agonists persisted, although we could not categorize these patients into any clear-cut platelet disorder. None of these 48 patients platelet associated immunoglobulin was increased by flow cytometry. It is possible that large number of patients from that disorder will finally prove to be some form of platelet secretory defect. In north India similar group of defect in a large number of patients have been reported as isolated PF3 abnormality or thrombasthenic thrombopathy.     

Platelet function tests using platelet aggregometry: need for repetition of the test for diagnosis of defective platelet function

Four hundred and ninety seven patients were referred to our center for platelet aggregation studies because of spontaneous mucocutaneous bleeds. All these patients had normal complete blood count, platelet count and peripheral smears except in ten patients of Bernard Soulier Syndrome where platelet count was marginally reduced in the presence of giant platelets. Two hundred and eighty patients were found to have normal platelet aggregation to ADP, collagen, ristocetin and arachidonic acid. Out of the remaining 217 patients, 62 patients were diagnosed to have Glanzmanns thrombasthenia, 10 Bernard Soulier Syndrome, 6 storage pool deficiencies, 7 cyclooxygenase deficiencies and 72 von Willebrand disease. In all the patients with GT and BSS, diagnosis was confirmed with flow cytometry using multiple monoclonal antibodies to GPIIb-IIIa and GPIb-IX. There were sixty patients where initial platelet aggregation studies showed reduced (<30%) aggregation to either ADP, collagen, ristocetin or arachidonic acid in its various combination, however in 12 such patients (20%) the platelet aggregation studies were normal on repetition. All our platelet aggregation studies were done only after assuring that the patient is not taking any medicine for at least 7-10 days which may affect the platelet function tests. The present study shows that single atypically abnormal platelet aggregation studies should always be repeated. Finally in 48/217 patients (22%) some aggregation abnormality to one or more of the agonists persisted, although we could not categorize these patients into any clear-cut platelet disorder. None of these 48 patients platelet associated immunoglobulin was increased by flow cytometry. It is possible that large number of patients from that disorder will finally prove to be some form of platelet secretory defect. In north India similar group of defect in a large number of patients have been reported as isolated PF3 abnormality or thrombasthenic thrombopathy.     

Inhibition of agonist-induced platelet aggregation by magnesium sulfate warrants its use as an alternative in vitro anticoagulant in pseudothrombocytopenia

Abstract

MgSO₄ is effective in preventing spontaneous in vitro platelet agglutination in anticoagulant-induced pseudothrombocytopenia (PTCP). In order to learn more about its potential as an in vitro anticoagulant, platelets from MgSO₄-anticoagulated blood were stimulated by several differentially-acting agonists (ADP, ARA, TRAP, epinephrine, collagen and ristocetin). Platelet aggregation in blood samples from 11 and 17 volunteers was measured by light-transmission aggregometry (LTA) according to Born and impedance aggregometry (Multiplate^TM), respectively. Agonist-induced platelet aggregation was markedly lower in MgSO₄-anticoagulated samples when compared with citrate-anticoagulated samples (decrease of 95.75% (ristocetin), 69.02% (collagen) and 75.73% (epinephrine)) or hirudin-anticoagulated samples (decrease of 85.99% (ADP), 80.98% (ARA), 77.24% (ristocetin), 54.37% (collagen) and 50.14% (TRAP)). The anti-aggregatory effect of MgSO₄ is dose-dependent and readily detectable at a concentration of 7.5 mmol/l. Analysis of the agonist signaling pathways suggest that MgSO₄ interferes with the final step of platelet aggregation, namely the intracellular mobilization of Ca²⁺.     

Clopidogrel anti-platelet effect: An evaluation by optical aggregometry,impedance aggregometry,and the Platelet Function Analyzer (PFA-100™)

Platelet aggregation inhibition by clopidogrel may be suboptimal in 4–30% of patients. Traditionally, optical aggregometry is used to assess clopidogrel's anti-platelet effects by inhibition of ADP-induced aggregation in platelet rich plasma. Red blood cells are an important source of ADP and, thus, are known to modulate platelet function. Because the whole blood aggregation by impedance method assesses platelet function in a physiological milieu, we compared clopidogrel response by this method with the optical method in platelet rich plasma (PRP) and the Platelet Function Analyzer (PFA-100?). Platelet function studies were performed in 17 healthy subjects at baseline and after 10 days of clopidogrel intake (75?mg/day). Optical and impedance aggregometry were performed after addition of ADP (10 and 20?µM) and collagen (1 and 2?µg/mL). For PFA-100? analysis, whole blood closure time was measured in collagen-coated cartridges with ADP and epinephrine. All subjects except one showed a decrease in ADP-induced aggregation using both aggregation methods. However, ADP-induced platelet aggregation was significantly inhibited when assessed in whole blood as compared to the optical method (71?±?34% vs. 34.2?±?23%, p?=?0.0002); this suggests that whole blood aggregometry is more sensitive in the detection of clopidogrel effect in the presence of red cells, which are known to modulate platelet function. The PFA-100? ADP closure time was slightly prolonged above the reference interval in only 5/17 (29%) subjects, suggesting that this instrument is not able to detect clopidogrel effect. We conclude that whole blood aggregation appears to be more sensitive in detecting clopidogrel effect compared with the platelet rich plasma method; the PFA-100? was unable to detect clopidogrel effect in the majority of the subjects.     

Studies investigating platelet aggregation and release initiated by sera from patients with thrombotic thrombocytopenic purpura

Many patients with thrombotic thrombocytopenic purpura (TTP) have a platelet aggregating factor in their serum that may be pathologically linked with the disease process. To help characterize the type of platelet aggregation and platelet release induced by the sera from seven TTP patients, we measured the ability of a variety of inhibitors of platelet function as well as the ability of monoclonal antibodies (MoAbs) against platelet glycoproteins to inhibit TTP sera-induced platelet aggregation and release. These results were compared with the ability of the same inhibitors to block platelet aggregation induced by ristocetin, collagen, ADP, thrombin, and IgG-immune complexes. Monoclonal antibody directed against platelet glycoprotein Ib totally inhibited ristocetin-induced aggregation and release but had no effect on aggregation and release induced by the TTP sera or by any of the other platelet agonists. However, the MoAb against glycoproteins IIb/IIIa inhibited aggregation and release caused by TTP sera as well as by collagen, thrombin, and ADP but had no effect on aggregation and release induced by ristocetin. The aggregating activity could be abolished by heparin but not by the serine protease inhibitor PMSF (1 mmol/L). And although monomeric human IgG and purified Fc fragments of IgG inhibited IgG-immune complex-induced aggregation and release, they had no effect on TTP sera-induced aggregation and release nor on aggregation and release induced by any of the other agonists. Consistent with these in vitro studies showing no effect of IgG were the in vivo observations that intravenous (IV) IgG was without effect when administered to three patients with TTP. This study indicates that although a von Willebrand factor (vWF)-rich preparation of cryoprecipitate enhances the in vitro platelet aggregation and release caused by sera from the seven TTP patients we studied, the pathway of aggregation and release is not via platelet glycoprotein Ib. Also the aggregating factor of TTP sera is not neutralized in vitro or in vivo by IgG.     

The effect of ex vivo anticoagulants on whole blood platelet aggregation

Pre- and intraoperative platelet function monitoring is increasingly recommended in order to detect risk factors for bleeding and to target coagulation management. The ideal anticoagulant for accurate platelet aggregometry remains controversial. The aim of this experimental trial was to compare platelet aggregability in whole blood stored in citrate, heparin and direct thrombin inhibitors. Whole blood was drawn from 11 healthy adult volunteers who had not taken any medication in the previous 14 days. Blood was stored in trisodium citrate, unfractionated heparin, melagatran, lepirudin and argatroban. Platelet aggregation was performed using the impedance aggregometer Multiplate® (Dynabyte, Munich, Germany) with adenosine diphosphate (ADP), thrombin receptor activating peptide (TRAP), collagen, arachidonic acid and ristocetin as agonists. Samples were analysed immediately after blood sampling (baseline), as well as 30 and 120 min afterwards. At baseline there were no significant differences in aggregability between samples containing direct thrombin inhibitors and heparin. In contrast, aggregation in response to all agonists except for ristocetin was significantly impaired in citrated blood. During storage the response to arachidonic acid and collagen was maintained by direct thrombin inhibitors and heparin, whereas ADP-, TRAP- and ristocetin-induced aggregation varied considerably over time in all ex vivo anticoagulants tested. Pre-analytical procedures should be standardized because storage duration and anticoagulants significantly affect platelet aggregability in whole blood. For point-of-care monitoring with immediate analysis after blood withdrawal all tested direct thrombin inhibitors as well as unfractionated heparin can be used as anticoagulants whereas citrate is not recommended.     

The possible value of platelet aggregation studies in patients with increased platelet number

Summary ADP, adrenalin and collagen platelet aggregation studies were performed in 54 patients with elevated platelet counts: 38 patients showed primary thrombocythemia and 16 secondary thrombocytosis. Patients with primary thrombocythemia (78.7%) showed a decreased aggregation pattern while in patients with secondary thrombocytosis platelet aggregation response was entirely normal. An increase in platelet aggregation was obtained in four patients with primary thrombocythemia. The platelet aggregation response did not appear to be related to circulating platelet number. A relationship between increased platelet aggregation and the occurrence of thrombosis was demonstrated. Similarly, a correction between impaired platelet aggregation and bleeding was also present. These results emphasize the diagnostic value of platelet aggregation studies in patients with elevated platelet number.Supported by grants from the M.P.I., Rome (grant 1592–1979), from the C.N.R., Rome (grant 78.012123.04) and from the Venetian Regional Government, Venice.     

Qualitative platelet defects in chronic myeloproliferative disorders: evidence for reduced ATP secretion

19 consecutive untreated patients with chronic myeloproliferative disorders and thrombocytosis were subjected to comprehensive platelet function tests including platelet aggregometry. 12 patients had essential thrombocythaemia (ET) and 7 patients had polycythaemia vera (PV). Bleeding time was normal. Arachidonic acid, collagen and ristocetin aggregation were abnormal only in a minority of patients, whereas ADP aggregation was impaired in 16 out of 19 patients. The most conspicuous findings were abolished second-wave adrenalin aggregation, increased ADP aggregation threshold, and markedly reduced ATP secretion during collagen-induced aggregation. This triad of qualitative platelet defects seems to be a good diagnostic marker of chronic myeloproliferative disease with thrombocytosis.     

Effects on platelet function of combination etoposide and carboplatin chemotherapy in pediatric oncology patients

The effects of a therapeutic course of the combination of carboplatin and etoposide on platelet function have been evaluated in 10 pediatric patients with brain tumors. Platelet count, in vitro aggregation tests, P-selectin expression and agonist-induced ATP release were evaluated before, and 7 and 15 days after one cycle of chemotherapy. The analysis of the results demonstrated the presence of an in vitro platelet aggregation defect in response to collagen and arachidonic acid in all patients 7 days after therapy. A concomitant decrease of collagen- and arachidonic acid-induced ATP release was also observed. Both platelet aggregation and ATP release returned to baseline values 15 days after chemotherapy administration. Conversely, in vitro platelet aggregation and secretion induced by ADP and epinephrine were unaltered by carboplatin and etoposide administration. Furthermore, P-selectin expression was negative at baseline and did not change after chemotherapy. These results support the hypothesis that combination etoposide and carboplatin chemotherapy in pediatric patients is responsible for possible disturbances in biochemical pathways required for platelet secretion and aggregation.     

The role of platelets in the coagulopathy of heatstroke- a study of platelet aggregation in heatstroke patients during the Makkah pilgrimage (Haj) to Makkah

Platelet aggregation was undertaken in platelet rich plasma in 34 heat-stroke patients during the Muslim pilgrimage (Haj) to Makkah; 18 were males and 16 were females; their ages ranged from 36 to 80 years (mean SD = 58 10). Platelet aggregability, on arrival at the Heatstroke Centres, was markedly inhibited in response to adrenaline, collagen, arachidonic acid and ristocetin but not to ADP. Responses to decreasing ADP doses (20.0, 2.0, 1.0 and 0.5 micromol/l) showed hyperaggregability in 12 patients, inhibited responses in 16 and normal responses in 6 patients. Aggregation responses were not significantly different when comparing patients with bleeding manifestations ( n = 10), with those without bleeding ( n = 24). Haemostatic parameters including plasma fibrinogen, ATIII and platelet count, were markedly reduced in the two patient groups who showed hyperaggrebable and depressed aggregation responses, but not in those with normal responses. These results lead us to conclude that: (1) platelet activation is a frequent feature of heatstroke; (2) in heatstroke altered aggregation responses, whether hyperaggregable or depressed, occur simultaneously with a consumption coagulopathy.     

Assessment of speed of an anti-platelet effect after two different doses of acetylsalicylic acid by flocculation

Acetylsalicylic acid inhibits aggregation of blood platelets through affecting arachidon acid metabolism--a precursor of thromboxan which is a strong platelet aggregation inhibitor. A standard method for measurement of aggregation activity blockade (in percents) of platelet rich plasma is turbidimetric aggregomethry based on spectrophotometric principle. According to results of recent studies administration of acetylsalicylic acid is one of the basic pillars of prevention of thrombotic complications in atherosclerotic arterial disease. Acetylsalicylic acid doses differ from study to study. An aim of our work was to measure speed of two different doses of acetylsalicylic acid. RESULTS: Level of aggregation activity blockade in samples of platelet rich plasma was measured by aggregometry in 26 healthy volunteers after administration of four inductors of thrombocyte aggregation (arachidon acid, adenosindiphosphate, collagen, and ristocetin). The samples were taken before administration and 120, 240, and 360 minutes after single peroral administration of 100 or 400 mg of acetylsalicylic acid. Samples of plasma were analysed immediately after sampling. Before drug administration there was no aggregation activity in 27.7% of the sample after arachidon acid administration, 28.3% after ADP administration, 21.5% after collagen administration and 25.3% after ristocetin administration. After administration of 400 mg of acetylsalicylic acid and administration of arachidon acid as an inductor 89.9% of the aggregation activity of the sample was blocked after 120 minutes, 89.6% after 240 minutes, and 90.6% after 360 minutes. After administration of adenosindiphosphate as an inductor 71.7% of the aggregation activity of the sample was blocked after 120 minutes, 68.3% after 240 minutes, and 69.9% after 360 minutes. And, after administration of ristocetin as an inductor 64% of the aggregation activity of the sample was blocked after 120 minutes, 66.4% after 240 minutes, and 54% after 360 minutes. Blockade of aggregation activity after collagen administration was not statistically significant. After administration of 100 mg of acetylsalicylic acid and administration of arachidon acid 83.8% of the aggregation activity of the sample was blocked after 120 minutes, 89.2% after 240 minutes, and 89.6% after 360 minutes. After adenosindiphosphate administration statistically significant blockade of aggregation activity was achieved after 360 minutes in the 56.7% of the sample. Also after collagen administration 42.5% of aggregation activity of the sample was blocked significantly after 360 minutes while ristocetin has not proved to influence aggregation in a statistically significant manner. CONCLUSION: Both doses of acetylsalicylic acid influenced aggregation activity of platelets in a statistically significant manner as soon as after 120 minutes following their peroral administration. However, they had different ability to influence platelets response to alternative ways of activation--by adenosindiphosphate, collagen, and ristocetin. 400 mg dose blocked these ways while 100 mg dose was efficient in blocking these ways after 360 minutes and in case of ristocetin--an inductor used to monitor platelet adhesion ability--100 mg dose has not led to statistically significant blockade at all.     

不同维持剂量氯吡格雷对择期经皮冠脉介入治疗患者术后血小板聚集率的影响

目的 探讨不同维持剂量氯吡格雷对择期经皮冠脉介入治疗(PCI)患者血小板聚集率的影响及其临床意义.方法 随机双盲将118例择期PCI患者分为A、B两组,术前600 mg负荷剂量相同,术后第1天开始分别给予不同剂量氯吡格雷(波立维、法国赛诺菲-安万特公司生产)75 mg/d或150 mg/d,于术前及术后1天、7天、14天和30天评估血小板聚集率.结果 A、B两组患者术前和术后1天ADP诱导的血小板聚集率和最大聚集时间比较无显著性差异,而术后7天、14天、30天比较差异有显著性.结论 较高剂量的氯吡格雷可以降低择期PCI患者的血小板聚集功能.     

Comparison of the pharmacodynamic effects of the platelet ADP receptor antagonists clopidogrel and AR-C69931MX in patients with ischaemic heart disease

We compared the antiplatelet effects of clopidogrel and the intravenous platelet P2Y 12 receptor antagonist AR-C69931MX, which acts on the same receptor as clopidogrel by a different and reversible mechanism and, unlike clopidogrel, is active in vitro . Thirteen patients with acute coronary syndromes entered into a phase II study of intravenous AR-C69931MX (Group 1) and eight patients undergoing intracoronary stent implantation and treated with clopidogrel (Group 2) were studied using a whole blood single-platelet counting aggregation assay. Group 2 patients were also studied using turbidimetry with ADP and TRAP as agonists and whole blood [ 14 C]5HT release to study dense granule secretion in response to ADP, collagen and TRAP. In Group 2 studies, a therapeutic concentration of AR-C69931MX was added in vitro before and after clopidogrel administration. AR-C69931MX in Group 1 achieved greater inhibition of ADP-induced platelet aggregation than clopidogrel in Group 2 and AR-C69931MX in vitro added to the effects of clopidogrel on ADP-induced aggregation. AR-C69931MX but not clopidogrel inhibited TRAP-induced aggregation and granule secretion and AR-C69931MX had a more consistent inhibitory effect on collagen-induced responses. In conclusion, therapeutic administration of clopidogrel moderately inhibits platelet P2Y 12 receptor activation and substantially greater P2Y 12 receptor blockade can be achieved with AR-C69931MX.