[Effect of original and generic clopidogrel on prognosis in relation to different gene polymorphisms]

AIM

To analyze the influence of clinical and pharmacogenetic factors on the risk of resistance to original or generic clopidogrel and that of cardiovascular events (CVE) during 12 months of follow-up.

SUBJECTS AND METHODS

Two hundred and fifty patients admitted to Moscow hospitals in October 2011 to September 2012 were examined. All the patients received clopidogrel. During their stay at hospital, venous blood samples were collected twice (before and 7-10 days after continuous clopidogrel intake). Platelet function was determined by optical aggregometry. A less than 10% reduction in platelet aggregation was taken as a resistance criterion. In addition, CYP2C9 and CYP2C19 gene polymorphisms were investigated.

RESULTS

Whether original or generic clopidogrel is used, the level of baseline or post-7-day ADP-induced platelet aggregation (ADP aggregation) fails to affect the risk of its resistance. Evaluation of ADP-induced platelet aggregation in patients with different CYP2C9 and CYP2C19 gene polymorphisms during the administration of original or generic clopidogrel also showed no significant differences in its resistance. During the 12-month follow-up, CVE significantly less frequently occurred as a result of the intake of original versus generic clopidogrel.

CONCLUSION

The use of original clopidogrel does not affect the risk of resistance to antiplatelet drugs, but it is associated with the lower incidence of CVE during a year.

[Comparative assessment of antiaggregant efficacy of acetylsalicylic acid and clopidogrel in peripheral atherosclerosis]

Presented in the article are the results of studying antiaggregate activity of acetylsalicylic acid and clopidogrel in a total of 36 patients suffering from various-severity chronic arterial insufficiency of lower limbs on the background of atherosclerosis obliterans. The study was conducted prior to treatment for correct selection of a particular antiplatelet agent. The obtained results showed that clopidogrel was not always more efficient than acetylsalicylic acid, since there is individual sensitivity of each patients to a particular antiplatelet agent. Therefore, an individual approach is necessary to conservative therapy of arterial insufficiency of lower limbs. For some patients it is preferable to administer clopidogrel, for others - acetylsalicylic acid. In a series of cases combined treatment is justified, while some patients having low sensitivity to both acetylsalicylic acid and clopidogrel require careful selection of alternative agents influencing other thrombocyte receptors.

[Factors influencing platelet aggregation in patients with acute coronary syndrome]

AIM

To study factors influencing platelet aggregation in patients with acute coronary syndrome (ACS).

SUBJECTS AND METHODS

The investigation enrolled 147 patients with ACS. Their blood was sampled on days 1, 3-5, and 8-12 days after the onset of ACS. All the patients received acetylsalicylic acid (ASA) 300 mg on day 1, then 100 mg/day and clopidogrel 300-600 mg on day 1, then 75-150 mg/day. Platelet aggregation was analyzed in 65 patients on day 1 after ASA intake, but prior to clopidogrel therapy. The aggregation was induced by 5 and 20 pmol of ADP.

RESULTS

With the use of clopidogrel 75 mg/day on day 3-5, platelet aggregation was reduced by 2.1 and 1.7 times for 5 and 20 μmol of ADP, respectively, as compared to day 1 (ASA without clopidogrel) and remained unchanged on days 8-12. Increasing the dose of clopidogrel up to 150 mg/day potentiated its antiaggregatory effect. On day 1 (ASA without clopidogrel), there was a direct correlation between platelet aggregation levels and mean platelet volume (MPV) (correlation coefficients (r), 0.526 (p < 0.001) and 0.368 (p = 0.015) for 5 and 20 μmol of ADP, and between platelet aggregation levels and glycoprotein (GP) IIb-IIIa (r = 0.387; p = 0.002 and r = 0.411 (p < 0.001) for 5 and 20 μmol of ADP. No similar correlations were found on days 3-5 and 8-12 of administration of ASA and clopidogrel. The genetic polymorphism of GP lIb-Illa (GP Ila Leu33Pro) was not noted to affect platelet aggregation. Examining the effects of genetic variations in cytochrome P450 isoform CYP2C19 (a clopidogrel metabolizer) revealed the enhanced aggregation stimulated with 20 μmol of ADP in the carriers of slowly clopidogrel-metabolizing haplotype of CYP2C19 (differences were found on days 3-5 as compared to rapidly and routinely metabolizing haplotypes).

CONCLUSION

In the patients with ACS, platelet aggregation is influenced by MPV, GP IIb-IIIa levels, and CYP2C19 polymorphism and is not by GP IIb-IIIa polymorphism.

What's new about clopidogrel

Clopidogrel is an oral tyenopiridin with a central role in the management of acute coronary syndromes and after stent implantation. Despite the use of this drug, many patients continue to experience thrombotic events which are usually referred as "therapy failure". Actually, to date, only stent thrombosis is considered therapy failure: mainly, it could be due to patient genetic predisposition or drug interaction, in particular with proton pump inhibitors. Genetic mutations in the CYP2C19 cytochrome (involved in the metabolism of clopidogrel and many other drugs) may lead to a lower concentration of active metabolites of the drug. In the same way, proton pump inhibitors interaction with the cytochrome may reduce clopidogrel activation. To overcome the problem some authors have suggested to increase the dosage of the drug, to use other drugs, to genotype patients, and not to use proton pomp inhibitors in patients on double antiplatelet therapy. Recent studies have shown that the interaction between clopidogrel and proton pump inhibitors is far to be clinically relevant and that the variability between the different assay to determine patients response to the drug does not allow, to date, to rely on their use. Moreover, double clopidogrel dose is as effective as low one in preventing major cardiovascular events, with a significant reduction in stent thrombosis in spite of a modest increase in major bleeding. Aim of this review article was to update current knowledge on clopidogrel, particularly focusing on the problem of "resistance" and PPI interaction. Moreover, we will discuss current strategies to overcome the resistance.

Pharmacokinetic and pharmacodynamic properties of batifiban coadministered with antithrombin agents in Chinese healthy volunteers

The combined use of batifiban, a synthetic platelet GPII b/ IIIa receptor antagonist, and antithrombin agents is an attractive option for the treatment of patients with non-ST-segment elevation (NSTE) acute coronary syndrome (ACS) and those scheduled for percutaneous coronary intervention. To observe whether antithrombin agents affect the pharmacokinetic and pharmacodynamic properties of batifiban in combination therapy and optimize clinical administration dosage of batifiban, an open-label and parallel study was conducted. Thirty healthy subjects were randomly divided into three groups, which were sequentially treated with batifiban alone, or oral coadministration of clopidogrel, aspirin and UFH, or batifiban coadministered with these antithrombin agents. Blood samples were collected at pre-specified time points. The evaluation index included the inhibition of platelet aggregation and pharmacokinetic parameters. The pharmacokinetic parameters of batifiban and batifiban coadministered with antithrombin agents showed no significant differences. The mean inhibition rate of platelet aggregation (%) suggested that neither batifiban alone nor antithrombin agents alone could provide such potent inhibition rate (>80%) to obtain the best clinical efficacy, but they had a synergistic effect on platelet inhibition. No serious adverse effects were observed. The results in these healthy subjects suggest that batifiban coadministrated with antithrombin agents could achieve optimum clinical treatment effect for patients with NSTE ACS, and also those scheduled for percutaneous coronary intervention.

Dual antiplatelet therapy -- management in general practice

BACKGROUND

Prasugrel and ticagrelor are two new antiplatelet agents being used in the management of acute coronary syndromes. The number of patients in the community managed on these medications is growing, and thus, it is essential that general practitioners have a good understanding of these agents and their evidence-based applications.

OBJECTIVE

The pharmacokinetic and pharmacodynamic properties of common and new antiplatelet agents will be reviewed, along with the evidence supporting their use. Safety and side effect profiles will be discussed, and some common general practice case scenarios presented.

DISCUSSION

Aspirin is still the mainstay of therapy in patients with acute coronary syndromes. The addition of clopidogrel, prasugrel or ticagrelor can reduce morbidity and mortality in selected patients. Patient factors including bleeding risk, renal function and time since coronary stent insertion must be reviewed before these agents are initiated and before making any changes to the medication regimen.

Purine pathway implicated in mechanism of resistance to aspirin therapy: pharmacometabolomics-informed pharmacogenomics

Although aspirin is a well-established antiplatelet agent, the mechanisms of aspirin resistance remain poorly understood. Metabolomics allows for measurement of hundreds of small molecules in biological samples, enabling detailed mapping of pathways involved in drug response. We defined the metabolic signature of aspirin exposure in subjects from the Heredity and Phenotype Intervention Heart Study. Many metabolites, including known aspirin catabolites, changed on exposure to aspirin, and pathway enrichment analysis identified purine metabolism as significantly affected by drug exposure. Furthermore, purines were associated with aspirin response, and poor responders had higher postaspirin adenosine and inosine levels than did good responders (n = 76; both P < 4 × 10(-3)). Using our established "pharmacometabolomics-informed pharmacogenomics" approach, we identified genetic variants in adenosine kinase associated with aspirin response. Combining metabolomics and genomics allowed for more comprehensive interrogation of mechanisms of variation in aspirin response--an important step toward personalized treatment approaches for cardiovascular disease.

Curcumin alters the pharmacokinetics of warfarin and clopidogrel in Wistar rats but has no effect on anticoagulation or antiplatelet aggregation

This study examined the effects of curcumin on the pharmacokinetic and pharmacodynamic properties of warfarin and clopidogrel in Wistar rats. Results showed that oral administration of curcumin at 25 mg/kg, 50 mg/kg, and 100 mg/kg for 7 days had no substantial effects on the pharmacodynamics of warfarin and clopidogrel in this animal model. However, oral administration of 100 mg/kg curcumin for 7 days significantly increased the AUC0-∞ and Cmax of the two drugs (by × 1.6 and × 1.5, respectively, for warfarin, and × 1.61 and × 1.81, respectively, for clopidogrel carboxylic acid). However, compared to warfarin alone, different doses of curcumin combined with warfarin had no effects on the prothrombin time in rats. Similarly, a combination of curcumin and clopidogrel had no significant effect on the maximum platelet aggregation rate of rats compared with the use of clopidogrel alone. This work demonstrated that preadministration of 100 mg/kg curcumin affected the pharmacokinetics of warfarin and clopidogrel but had no effect on pharmacodynamic parameters such as anticoagulation rate and antiplatelet aggregation.

Pharmacogenomics of anti-platelet therapy: how much evidence is enough for clinical implementation?

Pharmacogenomics, the study of the genomics of drug response and adverse effects, holds great promise for more effective individualized (personalized) medicine. Recent evidence supports a role of loss-of-function (LOF) variants in the cytochrome P450 enzyme CYP2C19 as a determinant of clopidogrel response. Patients given clopidogrel after percutaneous coronary intervention who carry LOF variants do not metabolize clopidogrel, a prodrug, into its active form resulting in decreased inhibition of platelet function and a higher likelihood of recurrent cardiovascular events. Despite a large body of evidence supporting clinical utility, adoption of anti-platelet pharmacogenetics into clinical practice has been slow. In this review, we summarize the pharmacokinetic, pharmacodynamic and clinical evidence, identify gaps in knowledge and other barriers that appear to be slowing adoption, and describe CYP2C19 pharmacogenetics implementation projects currently underway. Only when we surmount these barriers will clinicians be able to use pharmacogenetic information in conjunction with the history, physical examination and other medical tests and information to choose the most efficacious anti-platelet therapy for each individual patient.

Aspirin non-responder in Thai ischemic stroke patients

BACKGROUND

An important cause of recurrent ischemic stroke is failure to prevent secondary stroke due to poor control of important stroke risk factors. One of the proposed important risk factor is aspirin resistance. The prevalence of aspirin resistance varied widely. It depended on heterogeneity in studied populations and methods of platelet functional assessment.

OBJECTIVE

To describe the prevalence of aspirin resistance based on optical platelet aggregometry in stroke patients who attended the Neurological Institute and investigate the clinical risk factors associated with aspirin resistance.

MATERIAL AND METHOD

Three hundred stable ischemic stroke patients, whose aspirin dosage varied between 60 to 325 mg/day for at least 14 days before enrollment were recruited in the present study. Demographic data, modifiable risk factors, and treatment were collected by interview and from medical records. Aspirin resistance was determined by optical platelet aggregation technique, using arachidonicacid (AA) and adenosine diphosphate (ADP) as agonists.

RESULTS

The patients were classified into two groups based on their platelet aggregatometry tests (PAT). The cases group (n = 40, 13.3%) included both patients with aspirin resistance (n = 2, 0.6%) and aspirin semi-responsiveness (n = 38, 12.7%). The control group was aspirin non-resistance (n = 260, 86.7%). The cases were older (64.8 year vs. 61.26 year, p = 0.049), higher proportion of females (60% vs. 41.5%, p = 0.029), and shorter in height (159.9 CM vs. 164.1 CM, p = 0.007) than the control group. Dosage and duration of the aspirin therapy were the same in both groups. The multivariate analysis showed old age was associated with aspirin resistance.

CONCLUSION

The prevalence of aspirin resistance in the present study is 0.6% (95% CI, 0.18%-1.38%). The risk factor for aspirin resistance in post stroke patients is aging. No association between duration and aspirin dosage with aspirin resistance was found. The proportion of aspirin resistance was similar to a previous study done in post myocardial infarction patients.

Long-term outcome after angiographically proven coronary stent thrombosis

The long-term outcomes of patients with angiographically proved stent thrombosis (ST) are insufficiently known. The aim of this study was to evaluate the presentation and in-hospital and long-term outcomes of patients with angiographically proved ST as well as predictors of unfavorable clinical outcomes. One hundred six consecutive patients (mean age 69 ± 12 years, 85 men) presenting from 2003 to 2011 with 117 angiographically proved STs were included in the analysis. The time interval from initial stent implantation to ST, antiplatelet therapy at presentation, and the frequency and predictors of adverse events (death, myocardial infarction, and recurrent ST) during long-term follow-up (mean 65 ± 30 months) were evaluated. Eighty-six patients (80.9%) had early ST, 7 patients (6.6%) had late ST, and 13 patients (12.2%) had very late ST. Eighty-three patients (78.3%) were receiving dual-antiplatelet therapy at the time of ST. Eighty-three patients (78.3%) presented with ST-segment elevation myocardial infarctions, and 23 patients (21.6%) presented with other forms of acute coronary syndromes. Death rates during hospitalization, at 1 year, and at long-term follow-up were 17.9%, 23.8%, and 35.6%, respectively. The rates of recurrent definite ST during hospitalization, at 1 year, and at long-term follow-up were 7.5%, 9.9%, and 10.9%, respectively. Univariate predictors of the combined end point of death rate and definite recurrent ST were presentation with cardiogenic shock, left ventricular ejection fraction <30% at presentation, renal failure, discontinuation of clopidogrel administration at presentation, maximal creatine phosphokinase after ST, and Thrombolysis In Myocardial Infarction (TIMI) flow grade after intervention. Independent predictors of the primary end point at long-term follow-up remained cardiogenic shock (odds ratio [OR] 1.32, 95% confidence interval [CI] 1.08 to 1.63, p = 0.0069), renal failure (OR 1.26, 95% CI 1.01 to 1.57, p = 0.0425), and TIMI flow grade after intervention (OR 0.85, 95% CI 0.74 to 0.98, p = 0.0315). Current cigarette smoking was an independent predictor of repeat definite ST at long-term follow-up (OR 1.12, 95% CI 1.01 to 1.27, p = 0.0321). In conclusion, ST was associated with detrimental outcomes in the acute phase as well as the long-term phase. Recurrent ST was not infrequent.

Pharmacokinetics and pharmacodynamics of the antiplatelet combination aspirin (acetylsalicylic acid) plus extended-release dipyridamole are not altered by coadministration with the potent CYP2C19 inhibitor omeprazole

BACKGROUND

The fixed-dose combination of aspirin (acetylsalicylic acid) 25 mg plus extended-release dipyridamole 200 mg (ASA+ER-DP) is used for long-term secondary stroke prevention in patients who have experienced non-cardioembolic stroke or transient ischemic attack. Although the theoretical risk is low that the antiplatelet activity of ASA+ER-DP will be affected by concomitant use of a proton pump inhibitor (PPI), no formal drug-drug interaction studies have been conducted.

OBJECTIVE

This study aimed to determine whether the PPI omeprazole influences the pharmacokinetic (PK) and pharmacodynamic (PD) behavior of ASA+ER-DP.

STUDY DESIGN AND SETTING

This was a randomized, open-label, multiple-dose, crossover, drug-drug interaction study carried out in a clinical trial unit.

PARTICIPANTS

Sixty healthy male and female volunteers aged 18-50 years were included in the study.

INTERVENTION

Participants were randomized to one of two treatment sequences (ABCD or CDAB), each comprising four 7-day treatments with a washout of ≥14 days between the second and third treatments. Treatment A=ASA+ER-DP 25 mg/200 mg (Aggrenox®) twice daily (BID) alone; B=ASA+ER-DP 25 mg/200 mg BID+omeprazole (Prilosec®) 80 mg once daily (QD) following ASA+ER-DP alone for 7 days; C=omeprazole 80 mg QD alone; D=omeprazole 80 mg QD+ASA+ER-DP 25 mg/200 mg BID following omeprazole alone for 7 days.

MAIN OUTCOME MEASURES

The main outcome measures were systemic PK exposure to ER-DP and ASA inhibition of arachidonic acid-induced platelet aggregation.

RESULTS

Systemic exposure to ER-DP was similar with and without omeprazole, based on steady-state area under the concentration-time curve (AUC) from 0 to 12 h (AUC0-12,ss, ng·h/mL) and maximum plasma concentration (Cmax,ss, ng/mL). For the treatment comparison D versus A, the percent mean ratios were 96.38 (90% confidence interval [CI] 90.96-102.13) for AUC0-12,ss and 92.03 (86.95-97.40) for Cmax,ss. The ER-DP concentration versus time profiles were nearly superimposable. There was no effect on the PDs of the ASA component: the extent of ASA inhibition of arachidonic acid-induced platelet aggregation was almost identical with and without omeprazole, with a percent mean ratio for treatment D versus A = 99.02 (90 % CI 98.32-99.72) at 4 h after last dose. All treatments were well tolerated.

CONCLUSION

The PK and PD behavior of ASA + ER-DP was not altered by concurrent administration of omeprazole.

The Effects of Ergoloid Mesylates and Ginkgo Biloba on the Pharmacokinetics of Ticlopidine

Ticlopidine is sometimes coadministered with ergoloid mesylates or ginkgo biloba in clinical situations. Our objective was to examine the effect of ergoloid mesylates and ginkgo biloba on ticlopidine pharmacokinetics. Ticlopidine, ergoloid mesylates, and ginkgo biloba significantly inhibited the organic anion transporting polypeptide (OATP-B)-mediated uptake of [(3)H]-estrone-3-sulfate in a concentration-dependent manner. When ergoloid mesylates was coadministered with ticlopidine, the ticlopidine area under the plasma drug concentration-time profile (AUC) from 0 to 12 hours was decreased 30% and the peak plasma drug concentration (C(max)) was decreased 29%, compared with ticlopidine administration alone. There were no significant changes in the pharmacokinetic parameters of ticlopidine when it was coadministered with ginkgo biloba. In summary, ergoloid mesylates is a more potent inhibitor of OATP-B than is ginkgo biloba, and it can reduce the oral bioavailability of drugs transported by OATP-B. Ergoloid mesylates markedly decreased the AUC and C(max) of ticlopidine, probably by inhibiting the OATP-B-mediated uptake of ticlopidine during the intestinal absorption phase. The results support a new model of intestinal drug-drug interaction.

The effect of multiple doses of ketoconazole or rifampin on the single- and multiple-dose pharmacokinetics of vorapaxar

This randomized, open-label, parallel-group study evaluated the effects of multiple-dose ketoconazole or rifampin on the single- and multiple-dose pharmacokinetics of vorapaxar. Healthy subjects randomly received one of the following three treatments (N = 12/group): (1) ketoconazole 400 mg once daily (QD) for 28 days (Days 1-28) and single-dose vorapaxar 20 mg on Day 7 followed by vorapaxar 2.5 mg QD for 21 days (Days 8-28); (2) rifampin 600 mg QD for 28 days (Days 1-28) and single-dose vorapaxar 20 mg on Day 7 followed by vorapaxar 2.5 mg QD for 21 days (Days 8-28); and (3) placebo QD for 28 days (Days 1-28) and single-dose vorapaxar 20 mg on Day 7 followed by vorapaxar 2.5 mg QD for 21 days (Days 8-28). Ketoconazole increased the steady-state vorapaxar AUC(0-24 h) and C(max) by approximately twofold (GMR [90% CI]: 196% [173,222]; 193% [166,223], respectively), while rifampin decreased vorapaxar AUC(0-24 h) and C(max) by approximately 50% (GMR [90% CI]: 45.5% [40,52]; 61.4% [52,72], respectively) versus vorapaxar alone. Potent CYP3A4 inhibitors or inducers may cause moderate increases or decreases in vorapaxar exposure, respectively, which may have safety and/or efficacy implications; therefore, their concomitant use with vorapaxar is not recommended.

Open-label, dose-titration and continuation study to assess efficacy, safety, and pharmacokinetics of anagrelide in treatment-naïve Japanese patients with essential thrombocythemia

Although anagrelide is widely used for the treatment of essential thrombocythemia (ET) in the USA and Europe, it is not licensed in Japan. Existing literature has reported differences in polymorphism and activity of CYP1A2 in Japanese and non-Japanese ethnic groups, which may alter anagrelide metabolism. We intended to identify the optimum dosage of anagrelide in treatment-naïve Japanese patients with ET and assess its long-term safety and efficacy. Twelve patients with ET and a platelet count of ≥ 80 × 10(4)/μL were enrolled. Anagrelide was administered at an initial dose of 0.5 mg/day (weeks 1-4), then increased to 1.0 mg/day (weeks 5-8). During the following maintenance (weeks 9-52) and continuation periods (weeks 53-104), the dose was adjusted according to patient safety data and to maintain target platelet counts (<60 × 10(4)/μL). Increasing the dose led to a decrease in mean platelet count, and target platelet counts were maintained in 11 patients. Adverse events were mild or moderate, and none led to discontinuation. This cohort of Japanese patients exhibited higher pharmacokinetic exposures of anagrelide and its active metabolite than those previously documented in non-Japanese patients. These differences were modest, suggesting specific dosing regimens for Japanese patients are not required.

Spaced administration of PA32540 and clopidogrel results in greater platelet inhibition than synchronous administration of enteric-coated aspirin and enteric-coated omeprazole and clopidogrel

BACKGROUND

A common regimen for patients requiring dual-antiplatelet therapy who are at risk for gastrointestinal complications is the synchronous administration of enteric-coated (EC) aspirin, a proton pump inhibitor, and clopidogrel, although proton pump inhibitors have the potential for pharmacodynamic interaction with clopidogrel. Spaced administration of a clopidogrel and a single-tablet formulation of aspirin and immediate-release omeprazole (PA32540) was considered as an alternative that might reduce this potential pharmacodynamic interaction.

METHODS AND RESULTS

A randomized, open-label, crossover study was conducted in healthy subjects (n = 30). Two 7-day treatments were separated by 14-day washout periods: (a) PA32540 + clopidogrel (300 mg loading/75 mg maintenance) 10 hours later and (b) synchronous dosing of clopidogrel + EC aspirin (81 mg) + EC omeprazole (40 mg). The primary end point was the inhibition of platelet aggregation (20 μM adenosine diphosphate, maximal extent) after 7 days. CYP2C19 and ABCB1 genotypes were determined. Inhibition of platelet aggregation was greater with spaced PA32540 + clopidogrel therapy vs synchronous clopidogrel + EC aspirin + EC omeprazole therapy (P = .004). There was no difference in day 7 arachidonic acid-induced aggregation. The effect of spacing on pharmacodynamics was independent of genotype.

CONCLUSIONS

PA32540 and clopidogrel spaced 10 hours apart had greater antiplatelet effects than did synchronously administered EC aspirin (81 mg), clopidogrel (75 mg), and EC omeprazole in healthy volunteers. These finding are directly relevant to the treatment for patients with high gastrointestinal risk who require dual-antiplatelet therapy and gastroprotection.

Use of antiplatelet therapy after percutaneous coronary intervention with bare-metal stents and different types of drug-eluting stents

Dual antiplatelet therapy (DAPT) with a thienopyridine and aspirin has been the standard of care post coronary stent implantation. DAPT has been shown to reduce the risk of stent thrombosis (ST) and complications of myocardial infarction and death after placement of a drug-eluting stent (DES) and bare-metal stent (BMS). This article reviews the available clinical efficacy and safety data of antiplatelet therapies. The aim of this review is to highlight not only the importance of antiplatelets in the prevention of early and late thrombosis but also emphasize the importance of newer more potent antiplatelet agents and their role in the setting of clopidogrel resistance. MEDLINE, and EMBASE were searched for studies related to the clinical efficacy and safety of antiplatelet therapy after DES and BMS placement using the terms dual antiplatelet therapy, thienopyridine, aspirin, clopidogrel, prasugrel, ticagrelor,elinogrel, bare-metal stents, drug-eluting stent, stent thrombosis and myocardial infarction.

Platelet function normalization after a prasugrel loading-dose: time-dependent effect of platelet supplementation

BACKGROUND

Hemostatic benefits of platelet transfusions in thienopyridine-treated acute coronary syndrome (ACS) patients may be compromised by residual metabolite in circulation.

OBJECTIVES

To estimate the earliest time after a prasugrel loading-dose when added platelets are no longer inhibited by prasugrel's active metabolite.

METHODS

Baseline platelet reactivity of healthy subjects (n=25, 30 ± 5 years, 68% male) on ASA 325 mg was tested using maximum platelet aggregation (MPA, ADP 20 μm) and VerifyNow(®) P2Y12 and was followed by a 60 mg prasugrel loading-dose. At 2, 6, 12 and 24 h post-dose, fresh concentrated platelets from untreated donors were added ex-vivo to subjects' blood, raising platelet counts by 0% (control), 40%, 60% and 80%. To estimate the earliest time when prasugrel's active metabolite's inhibitory effect on the added platelets ceases, platelet function in supplemented samples was compared across time-points to identify the time when effect of supplementation on platelet function stabilized (i.e. the increase in platelet reactivity was statistically similar to that at the next time-point).

RESULTS

Supplemented samples showed concentration-dependent increases in platelet reactivity vs. respective controls by both MPA and VerifyNow(®) at all assessment time-points. For each supplementation level, platelet reactivity showed a sharp increase from 2 to 6 h but was stable (P=NS) between 6 and 12 h.

CONCLUSIONS

The earliest measured time when supplemented platelets were not inhibited by circulating active metabolite of prasugrel was 6 h after a prasugrel loading-dose. These findings may have important implications for prasugrel-treated ACS patients requiring platelet transfusions during surgery.

[Assessment of clinical and antiaggregation efficacy of generic clopidogrel 'Egithromb' in roentgenosurgical practice]

The authors studied efficacy of the generic clopidogrel Еgithromb manufactured by EGIS PHARMACEUTICALS (Hungary) based on clinical data and parameters of light aggregometry in a total of 30 patients subjected to planned subcutaneous coronary intervention for stable angina pectoris. It was noted that the generic clopidogrel Egithromb possesses clinical efficacy, manifesting in the lack of early thromboses of the stents and relapses of angina pectoris during the first month of treatment. The findings obtained by light aggregometry strongly suggested a significant decrease in aggregation with a dose of ADP 1.25 mcg/ml in 87.33% of patients, with the target values of the index less than 25% were obtained in 100% of cases. It was determined that the agent possesses high efficacy in aspirin-resistant patients and in the presence of thrombinemia. There were neither side events of therapy nor haemorrhagic complications in the present study during treatment.

Human target validation of phosphoinositide 3-kinase (PI3K)β: effects on platelets and insulin sensitivity, using AZD6482 a novel PI3Kβ inhibitor

BACKGROUND

Based on in vitro and animal data, PI3Kβ is given an important role in platelet adhesion and aggregation but its role in insulin signaling is unclear.

OBJECTIVE

To strengthen the PI3Kβ target validation using the novel, short-acting inhibitor AZD6482.

METHODS AND RESULTS

AZD6482 is a potent, selective and ATP competitive PI3Kβ inhibitor (IC(50) 0.01 μm). A maximal anti-platelet effect was achieved at 1 μm in the in vitro and ex vivo tests both in dog and in man. In dog, in vivo AZD6482 produced a complete anti-thrombotic effect without an increased bleeding time or blood loss. AZD6482 was well tolerated in healthy volunteers during a 3-h infusion. The ex vivo anti-platelet effect and minimal bleeding time prolongation in the dog model translated well to data obtained in healthy volunteers. AZD6482 inhibited insulin-induced human adipocyte glucose uptake in vitro (IC(50) of 4.4 μm). In the euglycemic hyperinsulinemic clamp model, in rats, glucose infusion rate was not affected at 2.3 μm but reduced by about 60% at a plasma exposure of 27 μm. In man, the homeostasis model analysis (HOMA) index increased by about 10-20% at the highest plasma concentration of 5.3 μm.

CONCLUSIONS

This is the first human target validation for PI3Kβ inhibition as anti-platelet therapy showing a mild and generalized antiplatelet effect attenuating but not completely inhibiting multiple signaling pathways with an impressive separation towards primary hemostasis. AZD6482 at 'supratherapeutic' plasma concentrations may attenuate insulin signaling, most likely through PI3Kα inhibition.

Pharmacokinetics of clopidogrel in healthy Chinese volunteers

There are marked ethnic variabilities in the metabolism of clopidogrel. The pharmacokinetic (PK) characteristics of clopidogrel have been studied previously in whites or Korean volunteers, but these PK characteristics may not be fully extrapolated to the Chinese people. Little is known about the PK characteristics of clopidogrel in Chinese population. The aim of this study was to evaluate the pharmacokinetic profiles of clopidogrel in 20 healthy Chinese volunteers after administration of a single dose of clopidogrel 75 mg. The peak plasma concentration (Cmax), time to Cmax (Tmax), area under the plasma concentration versus time curve from time 0 h to 36 h (AUC(0-36)), elimination half-life (t1/2), clearance rate (CL/F) and apparent volume of distribution (Vd) were (1.804 +/- 1.706) ng/ml, (0.7 +/- 0.3) h, (2.465 +/- 1.693) ng x h/ml, (7.3 +/- 7.0) h, (53.09 +/- 34.65) x 10(3) L/h and (447.1 +/- 440.8) x 10(3) L, respectively.

CYP2C19 681G > A polymorphism and pharmacokinetics of clopidogrel in Chinese healthy volunteers

The aim of this study was to investigate the contribution of the most frequent single nucleotide polymorphism of CYP2C19 681G>A to the pharmacokinetics of clopidogrel in 20 healthy Chinese volunteers after administration of a single dose of clopidogrel 75mg. The peak plasma concentration (Cmax) was higher in the 681GA+681AA group than that in the 681GG group (1.93 +/- 1.77 vs. 1.65 +/- 1.56ng/mL, P=0.613). The area under the curve to the last measurable concentration (AUC(0-36)) and area under the curve extrapolated to infinity (AUC(0-infinity)) of clopidogrel were lower in the 681GG group than that in the 681GA+ 681AA group (2.25 +/- 1.64 vs. 2.64 +/- 1.69 ng h/mL, P = 0.465; 2.26 +/- 1.65 vs. 2.67 +/- 1.71 ng h/mL, P = 0.455) respectively. The oral clearance (CI/F) was lower in the 681GA+681AA group than that in the 681GG group (51.96 +/- 36.13 vs. 54.47 +/- 35.21 x 10(3) L/h, P=0.829). The genetic polymorphism of CYP2C19 681G > A does not cause significant alterations in the pharmacokinetics of clopidogrel at a clinically relevant therapeutic dose in healthy Chinese volunteers.