Patients with both chronic kidney disease (CKD) and diabetes mellitus (DM) are at increased risk for thrombotic events compared to those with one abnormality alone. Whether this can be attributed to changes in platelet reactivity among those with both CKD and DM is unknown. We prospectively studied 438 clopidogrel-naïve patients undergoing percutaneous coronary intervention (PCI). Platelet function tests were performed 4-6 hours after loading with 600 mg of clopidogrel. Platelet reactivity was assessed using the VerifyNow system and expressed as P2Y12 reaction units (PRU). High residual platelet reactivity (HRPR) was defined as PRU > 230. Patients were categorised into four groups by the presence or absence of CKD and DM. Among those without CKD or DM (n=166), DM alone (n=150), CKD alone (n=60) and both CKD and DM (n=62) the mean PRU levels were 201.6 ± 96.3, 220.5 ± 101.1, 254.9 ± 106.7 and 275.0 ± 94.5, respectively (p<0.001). Analogously, the prevalence of HRPR was 42.3%, 50.7%, 63.3% and 75.8%, respectively (p< 0.001). Associations between either CKD or DM alone and HRPR were attenuated after multivariable adjustment while the odds for HRPR associated with both CKD and DM remained significant (OR [95% CI]: 2.61 [1.16 - 5.86]). In conclusion, the presence of both CKD and DM confers a synergistic impact on residual platelet reactivity when compared to either condition alone. Whether more potent platelet inhibitors may improve outcomes among patients with both abnormalities warrants investigation.

Objective We previously reported that the antiplatelet action is intensified with combined use of clopidogrel and cilostazol in ischemic stroke patients using the VerifyNow P2Y12 Assay. In this study, the relationship between the cilostazol dose and the platelet function achieved with combination therapy was investigated. Methods The subjects included 231 patients with noncardiogenic ischemic stroke treated at our hospital (18 patients treated with a combination of clopidogrel (75 mg) and cilostazol (100 mg), 52 patients treated with a combination of clopidogrel (75 mg) and cilostazol (200 mg), 126 patients treated with clopidogrel (75 mg) alone and 35 patients treated with cilostazol (200 mg) alone). The platelet function achieved with 20 μM of adenosine diphosphate was measured using the VerifyNow P2Y12 Assay. Clopidogrel resistance was defined as P2Y12 Reaction Units (PRU) >230 and/or % inhibition <20%. Results The PRU was >230 in 32 patients (25.4%) receiving clopidogrel alone, one patient (5.6%) receiving combination therapy with cilostazol (100 mg) and one patient (1.9%) receiving combination therapy with cilostazol (200 mg). The rate of PRU >230 was significantly lower in both of the cilostazol combination groups than in the clopidogrel alone group. The percent inhibition was <20% in 41 patients (32.5%) receiving clopidogrel alone, one patient (5.6%) receiving a combination with cilostazol (100 mg) and one patient (1.9%) receiving a combination with cilostazol (200 mg). The rate of % inhibition <20% was significantly lower in both of the cilostazol combination groups than in the clopidogrel alone group. Conclusion Clopidogrel resistance was clearly decreased with combination clopidogrel (75 mg) and low-dose (100 mg) cilostazol therapy. The use of combination therapy with clopidogrel and low-dose cilostazol may be one means of overcoming clopidogrel resistance.

Background-Prasugrel is a recently approved thienopyridine for use in patients with acute coronary syndromes undergoing percutaneous coronary intervention. There are no data on contemporary use of prasugrel in routine clinical practice.Methods and Results-We assessed the patterns of prasugrel use among 55 821 patients who underwent percutaneous coronary intervention and were discharged alive from January 2010 to December 2011 at 44 hospitals participating in the Blue Cross Blue Shield of Michigan Cardiovascular Consortium. Potential inappropriate therapy was defined as use in patients who had a history of cerebrovascular disease, weighed <60 kg, or were aged ≥75 years old. Clopidogrel was prescribed to 83% (n=46 574) and 17% (n=9247) of patients received prasugrel on hospital discharge. A steady, linear increase in prasugrel use was seen during the study period, with discharge prescription increasing from 8.4% in quarter 1 of 2010 to 22.3% in quarter 4 of 2011. Of the total cohort, 69.1% of patients presented with acute coronary syndrome, and in this group, 17.2% received prasugrel. Among patients prescribed prasugrel, 28.3% (n=2614) received the medication for indications outside of acute coronary syndromes. One or more known contraindications to the drug were present in 6% to 10% of patients discharged on this agent.Conclusions-There has been a steady increase in the use of prasugrel with the drug being used in ≈22% of patients undergoing percutaneous coronary intervention by study end. Prasugrel use in patients with known contraindications is not uncommon and may be a suitable target for focused quality improvement efforts.

Thrombocytopenia is often regarded as a risk factor for bleeding complications in patients undergoing percutaneous coronary intervention (PCI). The risk of mild to moderate baseline and acquired thrombocytopenia on bleeding and thrombotic or thromboembolic complications in patients with atrial fibrillation on oral anticoagulation therapy undergoing PCI, however, remains largely unknown. Management of Patients With Atrial Fibrillation undergoing Coronary Artery Stenting is a multicenter European prospective registry enrolling patients with atrial fibrillation undergoing PCI. We assessed the rate of bleeding complications as defined by Bleeding Academic Research Consortium and a composite of major adverse cardiac and cerebrovascular events (MACCE) including all-cause mortality, myocardial infarction, transient ischemic attack or stroke, stent thrombosis, systemic arterial embolism, or revascularization; and a composite of any harmful event (Bleeding Academic Research Consortium and MACCE) at 12-month follow-up in 861 consecutive patients undergoing PCI. Patients were divided into those with mild to moderate baseline thrombocytopenia (platelet count <150 × 10(9)/L; n = 99) and control group (platelet count >150 × 10(9)/L; n = 762). At hospital discharge, thrombocytopenia had no effect on prescribed antithrombotic treatment, and triple therapy (vitamin K antagonist + aspirin + clopidogrel) was the most common combination in both patient groups (69% vs 73%, p = 0.40). No differences in all-cause mortality (12% vs 11%, p = 0.79), MACCE (23% vs 22%, p = 0.87), or bleeding complications (23% vs 19%, p = 0.26) were detected. Acquired in-hospital thrombocytopenia occurred in 9.7% of patients, and it was associated with similar risk of adverse outcomes compared with control group. In conclusion, mild to moderate baseline thrombocytopenia does not seem to have a clinically significant effect on bleeding or thrombotic or thromboembolic complications after PCI in these frail patients receiving multiple antithrombotic drugs.

The considerable progress in P2Y12-platelet blockers has important perioperative implications due to a family of novel agents beyond clopidogrel. Although prasugrel is more potent than clopidogrel due to more efficient hepatic metabolism, it is limited clinically by its irreversibility and bleeding risks. Ticagrelor, as the first approved direct and reversible oral P2Y12 blocker, still is limited clinically by its novel side-effect profile. Intravenous reversible P2Y12 blockade is possible now with both cangrelor and elinogrel, although both agents are still in clinical development. Furthermore, elinogrel offers the possibility of both oral and parenteral P2Y12 blockade with a single agent. Future trials likely will continue to evaluate and compare the safety and efficacy of these agents in multiple clinical settings, including the perioperative period.

From 2010 to 2012 nine systematic reviews reported highly variable conclusions regarding the association between carriage of a cytochrome P450 2C19 loss-of-function allele and the risk of adverse cardiovascular events in individuals using clopidogrel. Possible contributors to the variable findings include differences in patient population, cardiovascular endpoints, and statistical models utilized by the systematic reviews, and unexplained heterogeneity, inconsistent/incomplete reporting, and risk of publication bias with respect to the primary studies.Clinical Pharmacology & Therapeutics (2013); accepted article preview online 13 May 2013; doi:10.1038/clpt.2013.100.

Spontaneous platelet aggregation was evaluated in patients with acute coronary syndrome on days 1, 3-5, and 8-12 of the disease. On day 1, aggregation was analyzed after aspirin, but before clopidogrel administration; during other periods after both antiaggregants. The mean levels of spontaneous aggregation after antithrombotic therapy did not change during different periods after the onset of acute coronary syndrome, in contrast to ADP-induced aggregation that decreased after the development of clopidogrel effects (days 3-5 and 8-12). Spontaneous aggregation during different periods directly correlated (r>0.4, p<0.01) with spontaneous and ADP-induced aggregation during different periods (r=0.372, r=0.447, and r=0.543 on days 1, 3-5, and 8-12, respectively; p<0.01). No relationship between spontaneous aggregation and plasma concentration of von Willebrand's factor was detected. Spontaneous aggregation was completely suppressed after in vitro addition of prostaglandin E1 (platelet activation inhibitor), slightly (by ≈20%) decreased in the presence of antibodies to glycoprotein Ib, blocking its reactions with von Willebrand's factor, and did not change in the presence of aptamer inhibiting thrombin activity.

The novel oral P2Y12 inhibitors (prasugrel and ticagrelor) have been incorporated into the recently updated acute coronary syndrome (ACS) guidelines, as an adjunct antiplatelet treatment to aspirin. The studies involving the use of new oral antiplatelet agents that are more potent, predictable and faster platelet inhibitors than clopidogrel have demonstrated superiority with respect to the primary composite endpoint (cardiovascular death, non-lethal myocardial infarction, stroke) for both prasugrel and ticagrelor compared to clopidogrel. The subgroup analysis of the relevant studies showed that these new agents differ in their level of efficacy in different ACS patient subgroups: (1) Mortality was reduced with ticagrelor; (2) Ticagrelor is especially more effective in intermediate-and high-risk non-ST elevation ACS patients in whom early invasive strategy is selected; (3) Prasugrel should be especially preferred in patients with acute ST elevation myocardial infarction undergoing percutaneous coronary intervention (PCI) after diagnostic angiography; and (4) Prasugrel is more effective in diabetic patients. While clopidogrel is recommended for ACS patients who are followed with a non-invasive strategy or who have not undergone percutaneous revascularization, it is the last line choice or an alternative to the P2Y12 inhibitor therapy for patients undergoing invasive strategy.

Aggressive dual antiplatelet therapy is associated not only with more bleeding, impaired wound healing, and potentially more solid cancer rates but it also causes higher infection risks including sepsis, and systemic inflammatory response syndrome (SIRS). This may be especially true considering the alarming off-label use of prasugrel. A 65-year-old white male patient with a history of myocardial infarction treated with percutaneous coronary intervention and implantation of 2 bare metal stents, was treated with off-label clopidogrel for 4 years, including a double daily dose (150 mg) for the initial 13 months. Still on clopidogrel, the patient was hospitalized with suspected pneumonia. A diagnostic cardiac catheterization revealed a 60%-70% blockage of the mid left anterior descending, but there was no need for coronary intervention. At discharge, clopidogrel 75 mg/d was switched over to off-label prasugrel 10 mg/d on top of aspirin (81 mg/d). On day 3 after prasugrel was given, a football-sized bruise appeared on the patient's lower right abdomen, but computed tomography results were unremarkable. On day 6 after administration of prasugrel, the patient became dizzy, disoriented, confused, experienced difficulty breathing, severe headache, weakness, intensive petechial rash covering the entire body, and breathing difficulty requiring ventilation. Within 24 hours, the patient was unable to correctly identify his age; his eyes were pale in color to almost colorless and when hearing a sound he would turn his entire head toward the sound and he appeared to be blind. His lungs, liver, and kidneys began to show signs of failure over the next 5-9 days. Sixteen days after the administration of the first prasugrel dose, the patient died of sepsis complicated with SIRS. Aggressive off-label use of clopidogrel (double dose for 13 months, and >4 years overall duration), followed by off-label switchover to the highest daily dose (10 mg) prasugrel may trigger sepsis and fatal SIRS. The mechanism responsible for such harmful association is probably indirect, and involves the weakening of platelet-neutrophil-endothelial crosstalk necessary to combat infections, and/or keep inflammation from spreading.