Inter-patient variability and impact of proton pump inhibitors on platelet reactivity after prasugrel

Resistance on the Latest Oral and Intravenous P2Y12 ADP Receptor Blockers in Patients with Acute Coronary Syndromes: Fact or Myth?

Novel P2Y12 ADP receptor blockers (ADPRB) should be preferred in dual-antiplatelet therapy in patients with acute coronary syndrome. Nevertheless, there are still patients who do not respond optimally to novel ADP receptor blocker therapy, and this nonoptimal response (so-called "high on-treatment platelet reactivity" or "resistance") could be connected with increased risk of adverse ischemic events, such as myocardial re-infarction, target lesion failure and stent thrombosis. In addition, several risk factors have been proposed as factors associated with the phenomenon of inadequate response on novel ADPRB. These include obesity, multivessel coronary artery disease, high pre-treatment platelet reactivity and impaired metabolic status for prasugrel, as well as elderly, concomitant therapy with beta-blockers, morphine and platelet count for ticagrelor. There is no literature report describing nonoptimal therapeutic response on cangrelor, and cangrelor therapy seems to be a possible approach for overcoming HTPR on prasugrel and ticagrelor. However, the optimal therapeutic management of "resistance" on novel ADPRB is not clear and this issue requires further research. This narrative review article discusses the phenomenon of high on-treatment platelet reactivity on novel ADPRB, its importance in clinical practice and approaches for its therapeutic overcoming.

Drug-Drug Interactions in Acute Coronary Syndrome Patients: Systematic Review

Drug-drug interaction (DDI) is defined as a clinically significant change in the exposure and/or response to a drug caused by co-administration of another drug which may result in a precipitation of an adverse event or alteration of its therapeutic effects. The aim of this systematic review was to provide an overview of DDIs that were actually observed or evaluated in acute coronary syndrome (ACS) patients with particular focus on DDIs with clinical relevance. Electronic searches of the literature were conducted in the following databases: MEDLINE, EBSCO, Scopus, Google Scholar and SCIndeks. A total of 117 articles were included in the review. This review showed that ACS patients can be exposed to a variety of DDIs with diverse outcomes which include decreased efficacy of antiplatelet drugs, thrombolytics or anticoagulants, increased risk of bleeding, rhabdomyolysis, hepatotoxicity, adverse effects on cardiovascular system (e.g. QT interval prolongation, arrhythmias, excessive bradycardia, severe hypotension), serotonin syndrome and drug-induced fever. Majority of the DDIs involved antiplatelet drugs (e.g. aspirin, clopidogrel and ticagrelor). Evidence of some of the reported DDIs is inconclusive as some of the studies have shown conflicting results. There is a need for additional post-marketing and population-based studies to evaluate the true effects of disease states and other factors on the clinical outcomes of DDIs. Clinicians should be attentive to the potential for DDIs and their associated harm in order to minimize or, if possible, avoid medication-related adverse events in ACS patients.

Protease-activated receptor-mediated platelet aggregation in acute coronary syndrome patients on potent P2Y12 inhibitors

BACKGROUND

Despite the increasing use of potent P2Y12 inhibitors, further atherothrombotic events still impair the prognosis of many acute coronary syndrome (ACS) patients. This may in part be attributable to intact platelet aggregation via the human thrombin receptors protease-activated receptor (PAR)-1 and PAR-4.

OBJECTIVE

We studied PAR mediated platelet aggregation in ACS patients following percutaneous coronary intervention (PCI) with stent implantation in a cross-sectional study.

METHODS

Platelet aggregation to ADP as well as to the PAR-1 agonist SFLLRN and the PAR-4 agonist AYPGKF was assessed by multiple electrode aggregometry in 194 ACS patients on dual antiplatelet therapy with aspirin and either prasugrel (n = 114) or ticagrelor (n = 80) 3 days after PCI.

RESULTS

Based on the consensus cutoff value, high on-treatment residual platelet reactivity to ADP (HRPR ADP) was observed in only 2 prasugrel-treated patients. Both patients with HRPR ADP had also a normal response to SFLLRN and AYPGKF. Among the 112 prasugrel-treated patients with adequate P2Y12 inhibition, 50 patients (45%) still had a normal response to SFLLRN, and 70 patients (63%) still had a normal response to AYPGKF. Among the 80 ticagrelor-treated patients with adequate P2Y12 inhibition, 25 patients (31%) still had a normal response to SFLLRN, and 50 (63%) still had a normal response to AYPGKF.

CONCLUSION

Normal platelet aggregation via PAR-1 and PAR-4 is preserved in many patients with adequate P2Y12 inhibition by prasugrel and ticagrelor. The present findings may at least in part explain adverse ischemic events despite potent P2Y12 inhibition.

Platelet reactivity and clinical outcomes in acute coronary syndrome patients treated with prasugrel and clopidogrel: a pre-specified exploratory analysis from the TROPICAL-ACS trial

Aims

The value of platelet function testing (PFT) in predicting clinical outcomes and guiding P2Y12-inhibitor treatment is uncertain. In a pre-specified sub-study of the TROPICAL-ACS trial, we assessed ischaemic and bleeding risks according to high platelet reactivity (HPR) and low platelet reactivity (LPR) to ADP in patients receiving uniform prasugrel vs. PFT-guided clopidogrel or prasugrel.

Methods and results

Acute coronary syndrome patients with PFT done 14 days after hospital discharge were included with prior randomization to uniform prasugrel for 12 months (control group, no treatment modification) vs. early de-escalation from prasugrel to clopidogrel and PFT-guided maintenance treatment (HPR: switch-back to prasugrel, non-HPR: clopidogrel). The composite ischaemic endpoint included cardiovascular death, myocardial infarction, or stroke, while key safety outcome was Bleeding Academic Research Consortium (BARC) 2–5 bleeding, from PFT until 12 months. We identified 2527 patients with PFT results available: 1266 were randomized to the guided and 1261 to the control group. Before treatment adjustment, HPR was more prevalent in the guided group (40% vs. 15%), while LPR was more common in control patients (27% vs. 11%). Compared to control patients without HPR on prasugrel (n = 1073), similar outcomes were observed in guided patients kept on clopidogrel [n = 755, hazard ratio (HR): 1.06 (0.57–1.95), P = 0.86] and also in patients with HPR on clopidogrel switched to prasugrel [n = 511, HR: 0.96 (0.47–1.96), P = 0.91]. In contrast, HPR on prasugrel was associated with a higher risk for ischaemic events in control patients [n = 188, HR: 2.16 (1.01–4.65), P = 0.049]. Low platelet reactivity was an independent predictor of bleeding [HR: 1.74 (1.18–2.56), P = 0.005], without interaction (Pint = 0.76) between study groups.

Conclusion

Based on this substudy of a randomized trial, selecting prasugrel or clopidogrel based on PFT resulted in similar ischaemic outcomes as uniform prasugrel therapy without HPR. Although infrequent, HPR on prasugrel was associated with increased risk of ischaemic events. Low platelet reactivity was a strong and independent predictor of bleeding both on prasugrel and clopidogrel.

Platelet reactivity in patients with acute coronary syndrome treated with prasugrel or ticagrelor in comparison to clopidogrel: a retrospective pharmacodynamic analysis

Dual antiplatelet therapy (DAPT) with aspirin and a P2Y₁₂ inhibitor is a mainstay of the prevention of stent thrombosis following percutaneous coronary intervention (PCI). In the 2015 European guidelines for the management of acute coronary syndrome (ACS), prasugrel (PRA) and ticagrelor (TICA) combined with aspirin are recommended as first-line therapy. Clopidogrel (CLO) is recommended as an alternative medication for patients with contradictions to these new drugs. This single-center study analyzed the platelet function of 809 ACS patients undergoing PCI and treatment with DAPT. The platelet response to ADP was determined using Multiplate® analyzer at a median of 3 days after PCI in 254 patients treated with PRA (loading dose [LD] 60 mg, 10 mg qd), 162 patients receiving TICA (LD 180 mg, D 90 mg bid), and 393 CLO-treated patients (LD 600 mg, 75 mg qd). An aggregation >468 arbitrary units (AU)*min was defined as "high on-treatment platelet reactivity" (HPR), <188 AU*min as "low on-treatment platelet reactivity" (LPR). Platelet response in PRA-treated patients was lower compared to CLO or TICA (median; interquartile range: PRA 220 [163-275] AU*min vs. CLO 268 [186-387] AU*min, p < 0.001 vs. TICA 245 [190-320] AU*min, p = 0.001). Only 1.6% of PRA patients were stratified as HPR and 34.6% as LPR, while in the TICA group 1.9% fulfilled the criteria of HPR and 24.1% criteria of LPR. Sixteen percent of CLO patients were stratified as HPR and 26.2% as LPR. In a real-world cohort of ACS patients following PCI, PRA results in more potent inhibition of platelet function compared to CLO and TICA. TICA achieves a consistent antiplatelet effect with reduced rates of HPR and LPR in relation to CLO.

Antiplatelet efficacy of prasugrel in patients with high on-clopidogrel treatment platelet reactivity and a history of coronary stenting

Little is known about the antiplatelet action of the 3rd generation thienopyridine prasugrel in patients showing high platelet reactivity (PR) levels on clopidogrel. Thus, we aimed to determine the antiplatelet efficacy of prasugrel loading (LD) and maintenance dose (MD) treatment in a registry of patients with high PR levels on clopidogrel and a consecutive switch over to prasugrel in a setting of routine platelet function testing. In our registry of patients treated by percutaneous coronary intervention (n=73) with high levels of PR on clopidogrel, the ADP-induced platelet aggregation (PA, in AU x min) was assessed on a Multiplate analyser 1) after clopidogrel LD, 2) after prasugrel LD and 3) on prasugrel MD (5 vs. 10 mg/day). In patients with high PR levels on clopidogrel, prasugrel LD resulted in significantly lower PA values (574 [462–698] vs. 156 [89–234] AU x min; p<0.0001). Only 2.7% of patients showed high PR (HPR, 468 AU x min) following prasugrel LD. On prasugrel MD, PA was significantly higher as compared to prasugrel LD (248 [145–406] vs. 156 [89–234] AU x min; p<0.0001) with more patients showing HPR on MD vs. LD (16.4% vs. 2.7%; p=0.009). For prasugrel MD, HPR rates were higher in 5 vs. 10 mg/day treated patients (46.2% vs. 10.0%; p=0.006). In conclusion, for patients with high PR levels on clopidogrel, prasugrel LD abolished this status in the majority of patients. However, prasugrel response variability was detected, being more pronounced on prasugrel MD vs. LD treatment. The clinical impact of these findings warrants further investigation.

Ticagrelor versus prasugrel in patients with high on-clopidogrel treatment platelet reactivity after PCI: The ISAR-ADAPT-PF study

Patients with high on-treatment platelet reactivity (HTPR) on clopidogrel are at high risk for adverse cardiovascular events after percutaneous coronary intervention (PCI). The aim of the ISAR-ADAPT-PF study was to assess the antiplatelet efficacy of ticagrelor versus prasugrel in patients with HTPR on clopidogrel. In a prospective and randomized clinical study, 70 patients with HTPR on clopidogrel loading dose (LD) within 24 h post PCI were assigned to receive either ticagrelor [180 mg LD followed by 90 mg maintenance dose (MD) twice daily] or prasugrel (60 mg LD followed by 10 mg MD once daily). The adenosine diphosphate-induced platelet aggregation assessed on the Multiplate analyzer on day 2 after randomization (primary end point) was as follows: the mean difference between the two treatment groups was 6 aggregation units (AU) × min with an upper 95% confidence interval (CI) of 41 AU × min, which was greater than the predefined noninferiority margin of 18 AU × min (P for noninferiority = 0.29). However, no significant differences in absolute platelet reactivity levels between ticagrelor- versus prasugrel-treated patients at that time point were observed (138 ± 100 AU × min vs. 132 ± 64 AU × min, P for superiority = 0.77). In conclusion, neither drug was statistically more effective for inhibition of platelet aggregation in patients with HTPR on clopidogrel post PCI, although the study could not formally demonstrate the assumed noninferiority of ticagrelor versus prasugrel.

Proton Pump Inhibitors in Cardiovascular Disease: Drug Interactions with Antiplatelet Drugs

Aspirin and P2Y₁₂ receptor antagonists are widely used across the spectrum of cardiovascular diseases. Upper gastrointestinal complications, including ulcer and bleeding, are relatively common during antiplatelet treatment and, therefore, concomitant proton pump inhibitor (PPI) treatment is often prescribed.PPIs provide gastroprotection by changing the intragastric milieu, essentially by raising intragastric pH. In recent years, it has been heavily discussed whether PPIs may reduce the cardiovascular protection by aspirin and, even more so, clopidogrel. Pharmacodynamic and pharmacokinetic studies suggested an interaction between PPIs and clopidogrel, and subsequent clinical studies were conducted to evaluate the clinical impact of this interaction. More recently, it was reported that PPIs may also attenuate the antiplatelet effect of aspirin. This may be clinically important, because a fixed combination of aspirin and a PPI (esomeprazole) has recently been approved and because aspirin is the most widely used drug in patients with cardiovascular disease. The antiplatelet effect of the new P2Y₁₂ receptor antagonists, ticagrelor and prasugrel, seems less influenced by PPI co-treatment.Given the large number of patients treated with antithrombotic drugs and PPIs, even a minor reduction of platelet inhibition potentially carries considerable clinical impact. The present book chapter summarizes the evidence regarding the widespread use of platelet inhibitors and PPIs in combination. Moreover, it outlines current evidence supporting or opposing drug interactions between these drugs and discusses clinical implications.

Predictors of high on-clopidogrel platelet reactivity in patients with acute coronary syndrome

High on-clopidogrel platelet reactivity (HPR) is a predictor of ischemic events after percutaneous coronary intervention. We conducted a prospective cohort study to identify variables related to HPR in acute coronary syndrome patients who are at high thrombotic risk. We enrolled 463 patients undergoing urgent coronary angiography. Platelet reactivity was measured 12-36 hours after 600 mg clopidogrel loading with multiple electrode aggregometry (Multiplate® analyzer, Roche, Basel, Switzerland, 6.4 µM ADP). HPR was defined by the consensus cut-off area under the curve >46 U. The rate of HPR was 16.0%. We analyzed simple clinical and laboratory parameters with backward multivariate logistic regression and identified the following predictors of HPR: platelet count (per G/L, OR: 1.0073, 95% CI: 1.0035-1.0112, p = 0.0002), CRP level (per mg/L, OR: 1.0077, 95% CI: 1.0016-1.01372, p = 0.01), and active smoking (OR: 0.51, 95% CI: 0.29-0.89, p = 0.02). We developed and internally validated a risk prediction model demonstrating moderate discriminative capacity (area-under-the-receiver operating characteristic curve = 0.67). In conclusion, we found a relatively low rate of high on-clopidogrel platelet reactivity (16.0%) even in an acute patient cohort. HPR measured by Multiplate was associated with high platelet count and CRP level on admission and was inversely related to active smoking. The model with rapidly available simple parameters might help to identify individuals at risk for HPR in the acute setting.

Prasugrel and ticagrelor: is there a winner?

Clopidogrel is a prodrug that undergoes extensive enteric clearance and requires two-stage hepatic activation by cytochrome P450 (CYP) enzymes. This metabolic pathway is susceptible to genetic polymorphisms, resulting in a variable platelet inhibitory effect. A growing number of studies have linked poor antiplatelet response to clopidogrel to adverse clinical outcomes, particularly coronary ischemic events and stent thrombosis. This has prompted the development of new ADP receptor antagonists that inhibit platelets more effectively. Two of these agents, prasugrel and ticagrelor, have been investigated in two large randomized clinical trials, and both have shown superiority versus clopidogrel in reducing ischemic endpoints, with an increase in bleeding events, but a favorable final net clinical outcome. Since the publication of the main articles, several sub-analyses have been performed on the same data, and Guideline recommendations have largely endorsed these subgroup findings. Most clinicians have accepted the concept that we might consider approaching the patient differently, deserving a specific agent for each different settings. However, subgroup analyses of randomized trials are often post hoc, underpowered and prone to bias. Weighing efficacy and safety of the most commonly used antiplatelet agents will represent a clinical challenge over the next few years. Furthermore, individuals and organizations involved in formulary decisions will have to face economic constraints, also taking into account the availability of low-cost generic clopidogrel. In the following review, we have performed a critical appraisal of the current literature in order to outline lights and shadows on the most relevant clinical scenarios.

A new mechanism of action of thienopyridine antiplatelet drugs - a role for gastric nitrosthiol metabolism?

This article outlines a new hypothesis that illustrates the potential role of the stomach (and subsequent chemical reactions involving nitrite therein) in modifying thienopyridines, such as clopidogrel. Gastric modification of thienopyridines can occur before standard accepted biotransformation pathways ensue. We hypothesised that thienopyridines expose the free thiol group once acidified (by the stomach) before biotransformation into active metabolites, and in the presence of nitrite (from saliva and the stomach) to form nitrosothiol derivatives (Thienopyridine induced-SNO formation). We have performed in vitro studies with each of the thienopyridines tablets/compounds confirming direct Th-SNO formation from the parent (inactive) drug by the following mechanism. Thienopyridine-SH + H(+ (Stomach)) +  [Formula: see text] ↔ Thienopyridine-SNO + H2O Thienopyridine-SNO (an S-nitrosothiol molecule) would have the potential to participate in all the reactions expected of native nitric oxide (NO) with added benefit that the NO "moiety" is protected, transportable and largely preserved from further reactive metabolism. All these biochemical steps are present in humans and could occur prior to enzymatic biotransformation.

Influence of proton pump inhibitors and VKORC1 mutations on CYP2C9-mediated dose requirements of vitamin K antagonist therapy: a pilot study

Interindividual variations in dose requirements of oral vitamin K antagonists (VKA) are attributed to several factors, including genetic variant alleles of vitamin K epoxide reductase complex subunit 1 (VKORC1) and cytochrome P450 2C9 (CYP2C9), but also interaction with co-medications. In this context, proton pump inhibitor (PPI)-related alterations of VKA maintenance dose requirements have been published. The present investigation aimed to test for an interaction profile of oral VKA-therapy and PPIs in relation to the CYP2C9 genotype. Median weekly stable VKA dose requirements over 1 year were recorded in 69 patients. Patients were genotyped for CYP2C9*2, CYP2C9*3, VKORC1c.-1639G>A and VKORC1c.174-136C>T and assessed for an association with PPI use and total VKA maintenance dose requirements. PPI users with CYP2C9 genetic variations required significantly lower weekly VKA maintenance doses than those with the wild-type genotype (t-test: P = 0·02). In contrast, in subjects without PPI use, the CYP2C9 genotype had no significant influence on oral VKA dose requirements. Further, the combined CYP2C9/VKORC1 genotype was a significant predictor for VKA dose requirements [linear regression: estimate: -1·47, standard error: 0·58 (P = 0·01)]. In conclusion, in carriers of CYP2C9 gene variations, the interference with the VKA metabolism is modified by PPI co-medication and the VCKORC1 genotype. Preceding knowledge of the genetic profile and the awareness for potentially occurring severe over-anticoagulation problems under PPI co-medication could contribute to a safer and personalized VKA pharmacotherapy.

Prasugrel but not high dose clopidogrel overcomes the lansoprazole neutralizing effect of P2Y12 inhibition: Results of the randomized DOSAPI study

AIMS

The potential negative metabolic interaction between proton pump inhibitors and clopidogrel is an unsolved issue. We hypothesized that doubling the clopidogrel maintenance dose (150 mg) would be less effective than switching to prasugrel 10 mg maintenance dose (MD) to overcome this negative interaction.

METHOD AND RESULTS

In a randomized study with a factorial design, 82 stable coronary artery disease patients treated with 75 mg clopidogrel MD and aspirin were assigned to receive in a double blind fashion lansoprazole (30 mg/day) or placebo and to receive in an open fashion 150 mg clopidogrel MD or 10 mg prasugrel MD. The primary endpoint was the relative change in residual platelet reactivity over the 14-day study period [(RPA14day-RPAbaseline)/RPAbaseline]. The effect of doubling the clopidogrel MD on relative change in RPA was neutralized by lansoprazole (-53.6±48.4% versus +0.8±53.7% without and with lansoprazole, respectively, p = 0.02) whereas 10 mg of prasugrel MD dramatically reduced RPA irrespective of lansoprazole co-administration (-81.8 %±24.8% vs. -72.9%±32.9% without and with lansoprazole, respectively, p = NS). Lansoprazole exposure was the only parameter with a significant interaction with RPA among subgroups.

CONCLUSION

The higher platelet inhibitory effect obtained by doubling the clopidogrel MD was totally neutralized by the co-administration of lansoprazole. This drug interaction was not observed with prasugrel 10 mg.

A comparative cohort study on personalised antiplatelet therapy in PCI-treated patients with high on-clopidogrel platelet reactivity. Results of the ISAR-HPR registry

In clopidogrel-treated patients undergoing percutaneous coronary intervention (PCI), high platelet reactivity (HPR) is associated with a higher risk for thrombotic events including stent thrombosis (ST). A personalised therapy with selective intensification of treatment may improve HPR patients´ outcome in this setting although recent randomised trials are against this hypothesis. The aim of the ISAR-HPR registry was to assess whether clopidogrel-treated HPR patients benefit from selective intensification of P2Y12 receptor inhibition. For the registry, outcomes were compared between two cohorts. We identified 428 clopidogrel treated HPR patients (AU x min ≥468 on the Multiplate analyser) between 2007-2008 (historical control cohort) without a change of treatment based on platelet function (PF) testing results. Between 2009-2011, we identified 571 HPR patients (guided therapy cohort) and used this information for guidance and selective intensification of P2Y12 receptor directed treatment (reloading with clopidogrel, switch to prasugrel, re-testing) in a setting of routine PF testing. The primary outcome was the composite of death from any cause or ST after 30 days. Major bleeding according to TIMI criteria was also monitored. The incidence of the primary outcome was significantly lower in the guided vs the control cohort (7 [1.2%] vs 16 [3.7%] events; HR 0.32, 95% CI 0.13-0.79; p=0.009). The incidence of major bleeding was numerically but not statistically higher in the guided vs the control cohort (1.9 vs 0.7%; p=0.10). In conclusion, present findings are in support for a PF testing guided antiplatelet therapy with selective intensification of P2Y12 receptor inhibition. The issue of personalised antiplatelet treatment warrants further investigation in randomized and well-controlled clinical trials.

Identification of PEAR1 SNPs and their influences on the variation in prasugrel pharmacodynamics

AIM

The present study aimed to investigate PEAR1 genetic polymorphisms and pharmacogenetic variability in the pharmacodynamics of prasugrel, a new oral antiplatelet agent, in healthy Han Chinese subjects.

PATIENTS & METHODS

The inhibition of adenosine diphosphate-induced platelet aggregation was measured pre- and post-administration using the VerifyNow(®) P2Y12 assay. The genetic sequence of PEAR1 exons and previously reported SNPs in the PEAR1 gene were investigated.

RESULTS

A total of 28 variations were identified in PEAR1. The SNPs in two regions of the PEAR1 gene, from rs3737224 to rs822442, and from rs1214331 to rs12566888, probably play important roles in prasugrel pharmacodynamics.

CONCLUSION

Further studies with larger sample sizes are recommended to explore the clinical importance of PEAR1 SNPs in prasugrel and other antiplatelet therapies. Original submitted 18 December 2012; Revision submitted 26 April 2013.

Antiplatelet drug interactions with proton pump inhibitors

INTRODUCTION

Non-aspirin antiplatelet agents (e.g., clopidogrel, prasugrel, ticagrelor) are commonly prescribed for the prevention of recurrent cardiovascular events among patients with acute coronary syndromes (ACS) and/or those undergoing percutaneous coronary intervention (PCI). In addition, combination therapy with proton pump inhibitors (PPIs) is often recommended to attenuate gastrointestinal bleeding risk, particularly during dual antiplatelet therapy (DAPT) with clopidogrel and aspirin. Importantly, a pharmacological interaction between clopidogrel and some PPIs has been proposed based on mutual CYP450-dependent metabolism, but available evidence is inconsistent.

AREAS COVERED

This article provides an overview of the currently approved antiplatelet agents and PPIs, including their metabolic pathways. Additionally, the CYP450 isoenzyme at the center of the drug interaction, CYP2C19, is described in detail, and the available evidence on both the potential pharmacological interaction and influence on clinical outcomes are summarized and evaluated.

EXPERT OPINION

Although concomitant DAPT and PPI use reduces clopidogrel active metabolite levels and ex vivo-measured platelet inhibition, the influence of the drug interaction on clinical outcomes has been conflicting and largely reported from non-randomized observational studies. Despite this inconsistency, a clinically important interaction cannot be definitively excluded, particularly among patient subgroups with higher overall cardiovascular risk and potentially among CYP2C19 loss-of-function allele carriers.

CYP-mediated pharmacologic interference with optimal platelet inhibition

Variability of response to clopidogrel and prasugrel is a multifactorial process, with clinical consequences, and drug-drug interactions have been proposed as potential factors. Biological modulation of clopidogrel response has been demonstrated for atorvastatin and omeprazole. However, investigations assessing clinical relevance of these findings have been heterogeneous, and real clinical impact is still debatable. For new P2Y12 blockers, such as prasugrel, with less variability of platelet inhibition, these interactions are not significant; accordingly, no dose adjustment is required. The present review aims to summarize available scientific evidence about CYP-mediated pharmacologic interference with optimal platelet inhibition in patients treated with thienopyridine.

Statements of the Malaysian Society of Gastroenterology & Hepatology and the National Heart Association of Malaysia task force 2012 working party on the use of antiplatelet therapy and proton pump inhibitors in the prevention of gastrointestinal bleeding

The working party statements aim to provide evidence and guidelines to practising doctors on the use of antiplatelet therapy and proton pump inhibitors (PPIs) in patients with cardiovascular risk as well as those at risk of gastrointestinal (GI) bleeding. Balancing the GI and cardiovascular risk and benefits of antiplatelet therapy and PPIs may sometimes pose a significant challenge to doctors. Concomitant use of anti-secretory medications has been shown to reduce the risk of GI bleeding but concerns have been raised on the potential interaction of PPIs and clopidogrel. Many new data have emerged on this topic but some can be confusing and at times controversial. These statements examined the supporting evidence in four main areas: rationale for antiplatelet therapy, risk factors of GI bleeding, PPI-clopidogrel interactions and timing for recommencing antiplatelet therapy after GI bleeding, and made appropriate recommendations.

Platelet reactivity in diabetic patients undergoing coronary stenting for acute coronary syndrome treated with clopidogrel loading dose followed by prasugrel maintenance therapy

BACKGROUND

Diabetes has been identified as a risk factor for impaired clopidogrel response, and these patients might have greater benefit with new P2Y12 blockers such as prasugrel. The present study was designed to assess response to thienopyridine in diabetic patients undergoing PCI for ACS.

METHODS AND RESULTS

107 diabetic patients undergoing PCI for ACS were included and treated by clopidogrel 600 mg loading dose and switched to prasugrel 10mg daily after PCI. Platelet reactivity was assessed by PRI VASP. High-on-treatment platelet reactivity (HTPR) was defined by PRI VASP>50% and Low-on-treatment platelet reactivity (LTPR) as PRI VASP below the 75th percentile (PRI VASP<20%). After clopidogrel, mean PRI VASP was 47 ± 21% and 54 patients (50%) were non responders. At one month, mean PRI VASP on prasugrel 10mg daily was 31 ± 13%, 9 patients (8%) had HTPR and 23 patients (22%) had LTPR. In multivariate analysis, factors associated with platelet reactivity were waist circumference for HTPR on clopidogrel and body weight for HTPR and LTPR on prasugrel. 10 patients (9%) suffered from BARC bleeding complications. Patients with bleeding complications had significantly lower PRI VASP values: 22 ± 9 vs. 32 ± 13, p=0.02 and ROC curves identified a cut-off value of VASP=28% to predict bleeding complications.

CONCLUSION

The present study confirmed that many diabetic patients treated with clopidogrel for ACS have inadequate platelet inhibition. Switch to prasugrel is effective with acceptable safety in this specific population. We observed a significant relationship between on-treatment platelet reactivity and bleeding complications.

Importance of potent P2Y(12) receptor blockade in acute myocardial infarction: focus on prasugrel

INTRODUCTION

Prasugrel therapy is recommended in patients with acute coronary syndromes (ACS) undergoing percutaneous coronary intervention (PCI).

AREAS COVERED

This article reviews the efficacy and safety profile of prasugrel, cost considerations, and its role in clinical practice based on published data. The authors searched PubMed and Ovid databases for English language clinical trial articles involving the use of prasugrel in human subjects and patients, published through June 2012. The keyword "prasugrel" was used. The review focuses on clinical trials, but other articles including Food and Drug Administration documents are also reviewed.

EXPERT OPINION

Prasugrel has a more rapid and greater pharmacodynamic (PD) effect than clopidogrel. No significant drug - drug interactions have been reported. In a large-scale randomized clinical trial, prasugrel was associated with better protection against ischemic event occurrence compared to clopidogrel, but more bleeding in ACS patients undergoing PCI. Adverse outcomes outweighed the benefit of prasugrel in certain subgroups, including patients over the age of 75, those weighing less than 60 kg, and patients with a prior history of stroke or transient ischemic attack. In subsequent PD studies, prasugrel therapy showed suboptimal platelet inhibition in selected patients. In addition, "hyper-responsiveness" to prasugrel may increase the risk of serious bleeding in high-risk patients. More detailed studies are warranted to explore antiplatelet regimens tailored to optimally limit ischemic and bleeding event occurrences. A Phase-III TRILOGY trial (NCT00699998) will indicate the clinical efficacy and safety of prasugrel in patients with non-ST-segment elevation ACS, who are medically managed without coronary revascularization.