A randomized study assessing the impact of cilostazol on platelet function profiles in patients with diabetes mellitus and coronary artery disease on dual antiplatelet therapy: results of the OPTIMUS-2 study

Flow diverters for intracranial aneurysms

Flow diverters (pipeline embolization device, Silk flow diverter, and Surpass flow diverter) have been developed to treat intracranial aneurysms. These endovascular devices are placed within the parent artery rather than the aneurysm sac. They take advantage of altering hemodynamics at the aneurysm/parent vessel interface, resulting in gradual thrombosis of the aneurysm occurring over time. Subsequent inflammatory response, healing, and endothelial growth shrink the aneurysm and reconstruct the parent artery lumen while preserving perforators and side branches in most cases. Flow diverters have already allowed treatment of previously untreatable wide neck and giant aneurysms. There are risks with flow diverters including in-stent thrombosis, perianeurysmal edema, distant and delayed hemorrhages, and perforator occlusions. Comparative efficacy and safety against other therapies are being studied in ongoing trials. Antiplatelet therapy is mandatory with flow diverters, which has highlighted the need for better evidence for monitoring and tailoring antiplatelet therapy. In this paper we review the devices, their uses, associated complications, evidence base, and ongoing studies.

Effect of Oral Anti-platelet Regimens on Platelet Aggregation using Chronolog Light Transmittance Aggregometry in Coronary Heart Disease Patients: An Observational Study

INTRODUCTION

Coronary heart disease is one of the most common cardiac health problem in India. Anti-platelet therapy is the cornerstone in the management of coronary heart disease. The current study was undertaken to compare the effect of different oral anti-platelet regimens on percentage inhibition of platelet aggregation in coronary heart disease patients using chronolog light transmittance aggregometry.

MATERIAL AND METHODS

Blood samples of 215 consecutive patients diagnosed of coronary heart disease (Male: Female ratio- 142: 73) with mean age of 55.2 ±10.3 years, who underwent platelet aggregation test were analysed. Patients were either on aspirin, clopidogrel, prasugrel, cilostazol or a combination of these drugs in different dosages. Of the 215 coronary heart disease patients, 35, 115 and 65 patients were on single, dual and triple anti-platelet drug regimen respectively.

RESULTS

The Percentage Inhibition of Platelet Aggregation (%IPA) in patients on dual anti-platelet regimen was highest i.e., 65.14 ± 23.23 as compared to 48.89 ± 22.16 in patients on monotherapy and 62.14 ± 21.64 in patients on triple anti-platelet regimen. Percentage of responders (> 40% inhibition of platelet aggregation) were 54.28%, 73.91% and 64.61% in single, dual and triple drug regimens respectively. Among responders on dual anti-platelet regimen, 64.7% were on aspirin + prasugrel and 35.3% were on aspirin + clopidogrel. The Percentage Inhibition of platelet aggregation in diabetics on dual anti-platelet regimen was 71.69 ± 17.54 as compared to 56.14 ± 23.29 in diabetics on triple anti-platelet regimen.

CONCLUSION

Dual anti-platelet therapy containing prasugrel was found to be more effective than dual anti-platelet therapy containing clopidogrel on background aspirin therapy and triple anti-platelet therapy in terms of percentage inhibition of platelet aggregation in coronary heart disease patients especially those with concomitant diabetes, however this conclusion needs to be further confirmed by large-scale randomized clinical trials.

Basics of Antithrombotic Therapy for Cardiovascular Disease: Pharmacologic Targets of Platelet Inhibitors and Anticoagulants

Arterial thrombus formation is the common pathophysiologic process of cardiovascular disease manifestations, requiring interplay between platelets and coagulation factors. Current platelet inhibitors block the formation of thromboxane A₂ and interfer with adenosine diphosphate stimulation mediated by the P2Y₁₂ receptor. Novel antiplatelet agents blocking these and other pathways are under clinical development. Thrombin represents a bridge between platelets and coagulation. Indirect and direct thrombin inhibitors are pivotal in clinical settings. Other key coagulation factors include factors IX and X which are therapeutic targets of current and novel anticoagulants. This article reviews the pathophysiology of arterial thrombosis and current and novel antiplatelet and anticoagulant agents.

Comparison of peri-procedural platelet inhibition with prasugrel versus adjunctive cilostazol to dual anti-platelet therapy in patients with ST segment elevation myocardial infarction

BACKGROUND

It has been well known that the inhibition of platelet aggregation (IPA) by anti-platelet agents was important to reduce the thrombo-embolic events in patients with ST segment elevation myocardial infarction (STEMI). However, the peri-procedural IPA by anti-platelet agents was not well known.

METHODS

We compared the peri-procedural IPA between prasugrel and adjunctive cilostazol to dual anti-platelet therapy (triple anti-platelet therapy; TAP) in patients with STEMI undergoing primary percutaneous coronary intervention (PCI). We prospectively randomized 70 consecutive clopidogrel-naive patients with STEMI planned PCI to either prasugrel [loading dose (LD) 60 mg; 37 patients] or TAP (LD aspirin 300 mg, clopidogrel 600 mg, and cilostazol 200mg; 33 patients). Primary end points of the study were the platelet reactivity unit (PRU) or % inhibition by the VerifyNow P2Y12 assay at pre-PCI and pre-discharge.

RESULTS

The drug loading to pre-PCI time was similar between prasugrel and TAP groups (25.4 ± 10.42 min vs. 25.5 ± 10.56 min, p=0.957). PRU at pre-PCI was significantly lower in prasugrel than in TAP (269.1 ± 71.69 vs. 306.5 ± 48.67, p=0.012). The lower PRU and greater % inhibition also observed in prasugrel than in TAP at pre-discharge (108.2 ± 60.51 vs. 238.1 ± 73.40; 63.6 ± 18.51% vs. 16.8 ± 17.91%, p<0.001 respectively). No differences in in-hospital bleeding complications between the two groups were observed.

CONCLUSION

Our study demonstrates that prasugrel could produce a significantly greater peri-procedural as well as in-hospital IPA compared with TAP in patients with STEMI undergoing primary PCI.

Effect of cilostazol on arterial stiffness and vascular adhesion molecules in type 2 diabetic patients with metabolic syndrome: a randomised, double-blind, placebo-controlled, crossover trial

BACKGROUND

The phosphodiesterase inhibitor cilostazol has beneficial effects on atherosclerosis by virtue of vasodilatory and antiplatelet effects. However, less is known about the effect of cilostazol on arterial stiffness and biochemical markers related to vascular inflammation and endothelial dysfunction in type 2 diabetic patients with metabolic syndrome.

METHODS

In this randomized, double-blind, crossover trial, 45 diabetic patients with metabolic syndrome were randomly assigned to either the cilostazol group (50 mg for 2 weeks, 100 mg for 6 weeks) or placebo group for an 8-week treatment phase, and then crossed over. Brachial-ankle pulse wave velocity (baPWV) and serum levels of inflammatory cytokines and vascular cellular adhesion molecules were measured before and after each treatment phase.

RESULTS

Compared with the placebo group, the mean baPWV did not improve in the cilostazol group (mean difference 31.42 cm/sec, 95% CI -55.67 to 118.5). Cilostazol treatment significantly reduced soluble vascular cellular adhesion molecule-1 (sVCAM-1) level (from 1288.7 ± 285.6 to 1168.2 ± 252.3 ng/dL, P = 0.0003), and there was also significant mean difference between groups (mean difference 105.18 ng/dL, 95% CI 10.65 to 199.71). However, other biochemical markers including lipid profiles, high sensitivity C-reactive protein, adiponectin, interleukin-6, tumor necrosis factor-alpha, monocyte chemotactic protein-1, and soluble intercellular adhesion molecule-1 did not improve with cilostazol treatment.

CONCLUSION

Cilostazol treatment significantly reduced serum sVCAM-1 level, but this short term treatment was not associated with beneficial effect on arterial stiffness and other inflammatory markers.

TRIAL REGISTRATION

(Clinical trial reg. no. NCT00573950, clinicaltrials.gov.).

Comparison of On-Treatment Platelet Reactivity Between Triple Antiplatelet Therapy With Cilostazol and Standard Dual Antiplatelet Therapy in Patients Undergoing Coronary Interventions

Background:

The recent literature has shown that triple antiplatelet therapy with cilostazol in addition to the standard dual antiplatelet therapy with aspirin and clopidogrel may reduce platelet reactivity and improve clinical outcomes following percutaneous coronary intervention. The purpose of this meta-analysis is to compare the efficacy of triple antiplatelet therapy and dual antiplatelet therapy in regard to on-treatment platelet reactivity.

Methods:

Nine studies (n = 2179) comparing on-treatment platelet reactivity between dual antiplatelet therapy (n = 1193) and triple antiplatelet therapy (n = 986) in patients undergoing percutaneous coronary intervention were included. Primary end points were P2Y12 reaction unit (PRU) and platelet reactivity index (PRI). Secondary end points were platelet aggregation with adenosine diphosphate (ADP) 5 and 20 µmol/L and P2Y12% inhibition. Mean difference (MD) and 95% confidence intervals (CI) were computed and 2-sided α error <.05 was considered as a level of significance.

Results:

Compared to dual antiplatelet therapy, triple antiplatelet therapy had significantly lower maximum platelet aggregation with ADP 5 µmol/L (MD: −14.4, CI: −21.6 to −7.2, P < .001) and 20 µmol/L (MD: −14.9, CI: −22.9 to −6.8, P < .001), significantly lower PRUs (MD: −45, CI: −59.4 to −30.6, P < .001) and PRI (MD: −26, CI: −36.8 to −15.2, P < .001), and significantly higher P2Y12% inhibition (MD: 18.5, CI: 2.3 to 34.6, P = .025).

Conclusion:

Addition of cilostazol to conventional dual antiplatelet therapy significantly lowers platelet reactivity and may explain a decrease in thromboembolic events following coronary intervention; however, additional studies evaluating clinical outcomes will be helpful to determine the benefit of triple antiplatelet therapy.

Platelet-function testing in patients undergoing neurovascular procedures: caught between a rock and a hard place

In the context of neurointerventional procedures, clopidogrel hyper-responsiveness has been associated with hemorrhage; on the other hand, clopidogrel resistance has been associated with thromboembolism. This might seem to make a compelling argument in favor of routine platelet testing. Our reading of the literature leads us to conclude that routine platelet testing in neurointerventional procedures is not, unfortunately, ready for prime time.

Platelet function profiles in patients with diabetes mellitus

Patients with diabetes mellitus (DM) are at high risk for several cardiovascular disorders such as coronary heart disease, stroke, peripheral arterial disease, and congestive heart failure. DM has reached epidemic proportions and its strong association with coronary artery disease is responsible for increased cardiovascular morbidity and mortality. DM patients are characterized by platelet hyperreactivity, which contribute to the enhanced atherothrombotic risk of these subjects. Several mechanisms are involved in the hyperreactive platelet phenotype characterizing DM patients. Furthermore, a large proportion of DM patients show inadequate response to standard antiplatelet treatments and high rate of adverse recurrent cardiovascular events despite compliance with standard antiplatelet treatment regimens. Therefore, new antiplatelet treatment regimens are warranted in DM patients to reduce their atherothrombotic risk. The present manuscript provides an overview on the current status of knowledge on platelet function profiles in patients with DM and therapeutic considerations.

Adjunctive cilostazol versus high maintenance dose of clopidogrel in patients with hyporesponsiveness to chronic clopidogrel therapy

PURPOSE

Whether addition of cilostazol is superior to increasing dose of clopidogrel in patients with hyporesponsiveness to chronic clopidogrel therapy is unknown.

MATERIALS AND METHODS

We studied 73 patients with hyporesponsiveness to clopidogrel on standard dual antiplatelet therapy for more than 2 weeks. Clopidogrel hyporesponsiveness was defined as percent inhibition of P2Y12 reaction units (PRU) <30% on VerifyNow P2Y12 assay. Patients were randomly assigned to increased dose of clopidogrel (aspirin 100 mg+clopidogrel 150 mg daily: group A, n=38) or to receiving additional cilostazol (aspirin 100 mg+clopidogrel 75 mg+cilostazol 100 mg bid daily: group B, n=35).

RESULTS

Baseline percent inhibition of PRU and PRU was similar between 2 groups (13.0 ± 10.2% versus 11.8 ± 9.7%, p = 0.61, and 286.3 ± 54.7 versus 295.7 ± 53.7, p=0.44, respectively). At follow-up, percent inhibition of PRU was higher and PRU was lower significantly in group B than in group A (38.5 ± 17.9% versus 28.3 ± 16.6%, p=0.02, and 207.3 ± 68.2 versus 241.3 ± 76.7, p=0.050, respectively). Among those still showing hyporesponsiveness to clopidogrel at follow-up (21 patients in group A, 10 patients in group B), 12 patients completed further crossover study. Compared to the baseline, magnitude of change in percent inhibition of PRU and PRU showed an improved tendency after the crossover (from 2.7 ± 8.7% to 15.8 ± 18.4%, p=0.08, and from -18.6 ± 58.0 to -61.9 ± 84.3, p=0.08).

CONCLUSION

Adjunctive cilostazol improved clopidogrel responsiveness better than the higher maintenance dose of clopidogrel in hyporesponsive patients with chronic clopidogrel therapy.

Genetic determinants of clopidogrel responsiveness in Koreans treated with drug-eluting stents

BACKGROUND

Variations of genes encoding cytochrome enzymes, drug transporters, and paraoxonase have recently been reported to be associated with clopidogrel response variability besides the well-known CYP2C19 loss-of-function (LOF) alleles. We determined whether newly reported genetic variations are associated with clopidogrel on-treatment platelet reactivity (OPR) in Korean patients.

METHODS

OPR was measured in 1264 consecutive patients who underwent percutaneous coronary intervention using the VerifyNowP2Y12 assay system and genotyping of PON-1 Q192R, ABCB1 C3435T, CYP1A2*1F, CYP2B6*6, CYP2C19*2, CYP2C19*3, CYP2C19*17, CYP3A4 (IVS10+12G>A), and CYP3A5*3 was performed. We applied two different cutoffs, i.e. 240 P2Y12 reaction units (PRU) and 253 PRU, to define high OPR.

RESULTS

Mean OPR of the entire population was 231±83 PRU. Genetic variations of ABCB1 and PON-1 genes as well as that of CYP1A2, 2B6, 3A4, and 3A5 were not associated with clopidogrel response variability. As for CYP2C19, patients were classified into 4 metabolism genotypes: 0.6% ultrarapid (UM), 40.3% extensive (EM), 48.8% intermediate (IM), and 10.3% poor metabolizers (PM). After adjustment for possible confounders, CYP2C19 metabolism genotype was associated with a significant increase in OPR: effect on OPR-difference: +27 PRU, p=0.015 for EM, +53 PRU, p<0.001 for IM, and +74 PRU, p=0.006 for PM compared with UM. In multivariable analysis, the CYP2C19 genotype was the only independent predictor of high-OPR among genetic variations using two different cutoffs.

CONCLUSIONS

Among genes postulated to be involved in clopidogrel metabolism, only the CYP2C19 genotype is associated with response variability and emerged as an independent predictor of high-OPR using two different cutoffs. PON-1 and ABCB1 genetic variants do not affect clopidogrel OPR in Korean patients.

Effect of tailored antiplatelet therapy on periprocedural myonecrosis in patients with diabetes mellitus (from the DM-Verify Now Trial)

We investigated whether additional platelet inhibition with a glycoprotein IIb/IIIa inhibitor would be beneficial in reducing the risk of periprocedural myocardial infarction (PMI) in diabetic patients with high residual platelet reactivity (HPR). Patients with diabetes mellitus were administered aspirin and clopidogrel at a 300-mg loading dose 1 day before the procedure, and the VerifyNow P2Y(12) assay was performed just before percutaneous coronary intervention. Patients with HPR, defined as a P2Y(12) reaction unit of ≥270 were randomly assigned to group A or control group C1. Patients without HPR were assigned to control group C2. Conventional anticoagulation with heparin was given to groups C1 and C2, and group A received additional abciximab treatment. Clinically relevant PMI was defined as any elevation in the biomarkers creatine kinase-MB isoenzyme and cardiac troponin I >3 times the upper normal limit measured 8, 16, or 24 hours after percutaneous coronary intervention. Of the patients, 47 and 51 were assigned to group A and C1; the clinical and procedural characteristics in the 2 groups were balanced. Of the 47 patients in group A and 51 patients in group C1, 9 (19%) and 9 (18%), respectively, experienced a PMI event according to the creatine kinase-MB cutoff (p = 1.00), and 27 in group A (57%) and 29 in group C1 (57%) experienced a PMI event according to the troponin I cutoff (p = 1.00). Five minor bleeding events, including small and localized hematomas, were observed immediately after the procedure (4 in group A and 1 in group C1). Only 1 major bleeding event, retroperitoneal hemorrhage, was observed in group A. The patients in group C2 had a PMI event rate (50% of 32 patients, p = 1.00) similar to that of group C1. In conclusion, additional platelet inhibition using a tailored approach and a point-of-care assay did not improve the periprocedural outcome in diabetic patients with HPR.

In vitro platelet antiaggregatory properties of 4-methylcoumarins

Platelets play a crucial role in physiological haemostasis. However, in coronary arteries damaged by atherosclerosis, enhanced platelet aggregation, with subsequent thrombus formation, is a precipitating factor in acute myocardial infarction. Current therapeutic approaches are able to reduce approximately one quarter of cardiovascular events, but they are associated with an increased risk of bleeding and in some resistant patients are not efficient. Some coumarins possess antiplatelet activity and, due to their additional antioxidant effects, may be promising drugs for use in combination with the present therapeutic agents. The aim of this study was to analyse a series of simple 4-methylcoumarins for their antiplatelet activity. Human plasma platelet suspensions were treated with different aggregation inducers [arachidonic acid (AA), collagen and ADP] in the presence of the 4-methylcoumarins. Complementary experiments were performed to explain the mechanism of action. 5,7-Dihydroxy-4-methylcoumarins, in particular those containing a lipophilic side chain at C-3, reached the activity of acetylsalicylic acid on AA-induced aggregation. Other tested coumarins were less active. Some of the tested compounds mildly inhibited either collagen- or ADP-induced aggregation. 5,7-Dihydroxy-4-methylcoumarins did not interfere with the function of thromboxane synthase, but were competitive antagonists of thromboxane A(2) receptors and inhibited cyclooxygenase-1 as well. 5,7-Dihydroxy-4-methylcoumarins appear to be promising candidates for the extension of the current spectrum of antiplatelet drugs.

Interaction analysis between genetic polymorphisms and pharmacodynamic effect in patients treated with adjunctive cilostazol to dual antiplatelet therapy: results of the ACCEL-TRIPLE (Accelerated Platelet Inhibition by Triple Antiplatelet Therapy According to Gene Polymorphism) study

WHAT IS ALREADY KNOWN ABOUT THIS SUBJECT

Compared with standard dual antiplatelet therapy, adjunctive cilostazol to dual antiplatelet therapy ('triple antiplatelet therapy') has a potential to reduce ischemic event occurrence after percutaneous coronary intervention. The pharmacokinetic and pharmacodynamic effects of clopidogrel have been significantly influenced by the enzyme activity of the ABCB1 C3435T and the CYP2C19 system. • For the pharmacokinetics of cilostazol, genetic polymorphisms of the CYP3A5 and CYP2C19 have been associated with the substantial interindividual variability in healthy volunteers.

WHAT THIS STUDY ADDS

Loss-of-function polymorphism of the CYP2C19 gene, but not the ABCB1 C3435T and CYP3A5*3 genes, affects the antiplatelet effect of triple antiplatelet therapy. Most of extensive and intermediate East Asian metabolizers (0 or 1 CYP2C19 loss-of-function allele) show adequate platelet inhibition when treated with triple antiplatelet therapy after percutaneous coronary intervention. However, carriage of 2 CYP2C19 loss-of-function alleles is still associated with the risk of high platelet reactivity (defined by by 5 µM ADP-induced maximal platelet aggregation >46%), which clinical impact needs to be validated in future clinical trials. AIMS Although adjunctive cilostazol to dual antiplatelet therapy can reduce the risks of clinical events after percutaneous coronary intervention (PCI), whether genetic polymorphism can influence the pharmacodynamics of this regimen has not been evaluated.

METHODS

One hundred and twenty-seven patients treated with PCI and taking triple antiplatelet therapy (≥1 month) were enrolled. Platelet reactivity was assessed by conventional aggregometry and the VerifyNow P2Y12 assay. High on-treatment platelet reactivity (HPR) was defined as 5 µm ADP-induced maximal platelet reactivity (Agg(max) ) >46%. CYP3A5*3, CYP2C19*2/*3 and ABCB1 3435C > T were genotyped.

RESULTS

CYP3A5*3 and ABCB1 3435C > T variants did not affect the antiplatelet effect of triple antiplatelet therapy. For non-carriers, one and two carriers of the CYP2C19 loss-of-function (LOF) allele, Agg(max) consecutively increased after the addition of 5 µm[mean (95% confidence intervals): 24.6% (20.8 to 28.5%) vs. 28.7% (25.4 to 32.0%) vs. 32.3% (25.8 to 38.7%), P = 0.062, respectively] and 20 µm ADP [34.2% (29.3 to 39.0%) vs. 41.7% (37.8 to 45.6%) vs. 44.9% (37.9 to 51.9%), P = 0.007, respectively]. Likewise, late platelet reactivity and P2Y12 reaction units proportionally changed according to the number of CYP2C19 LOF alleles. HPRs were observed in 9.2% of subjects: 6.3%, 7.4% and 20.0% with 0, 1 and 2 carriers of CYP2C19 LOF allele(s) (P = 0.099). In multivariate analysis, carriage of two CYP2C19 LOF alleles was a significant predictor for the prevalence of HPR (odds ratio 5.78, 95% CI 1.21, 27.78, P = 0.028).

CONCLUSION

Among PCI-treated patients, the effect of triple antiplatelet therapy is influenced by the CYP2C19 LOF allele. Its clinical benefit needs to be validated according to the CYP2C19 metabolic phenotype in future clinical trials. [Adjunctive Cilostazol Versus High Maintenance dose ClopidogrEL in Acute Myocardial Infarction Patients According to CYP2C19 Polymorphism (ACCEL-AMI-2C19), NCT00915733 and Adjunctive Cilostazol Versus High Maintenance-dose Clopidogrel According to Cytochrome 2C19 Polymorphism (ACCEL-2C19), NCT01012193].

Newer agents in antiplatelet therapy: a review

Antiplatelet therapy remains the mainstay in preventing aberrant platelet activation in pathophysiological conditions such as myocardial infarction, ischemia, and stroke. Although there has been significant advancement in antiplatelet therapeutic approaches, aspirin still remains the gold standard treatment in the clinical setting. Limitations in safety, efficacy, and tolerability have precluded many of the antiplatelet inhibitors from use in patients. Unforeseen incidences of increased bleeding risk and recurrent arterial thrombosis observed in patients have hampered the development of superior next generation antiplatelet therapies. The pharmacokinetic and pharmacodynamic profiles have also limited the effectiveness of a number of antiplatelet inhibitors currently in use due to variability in metabolism, time to onset, and reversibility. A focused effort in the development of newer antiplatelet therapies to address some of these shortcomings has resulted in a significant number of potential antiplatelet drugs which target enzymes (phosphodiesterase, cyclooxygenase), receptors (purinergic, prostaglandins, protease-activated receptors, thromboxane), and glycoproteins (αIIbβ3, GPVI, vWF, GPIb) in the platelet. The validation and search for newer antiplatelet therapeutic approaches proven to be superior to aspirin is still ongoing and should yield a better pharmacodynamic profile with fewer untoward side-effects to what is currently in use today.

Use of Cilostazol in Percutaneous Coronary Interventions

OBJECTIVE:

To evaluate the addition of cilostazol to standard dual antiplatelet therapy (DAT) with aspirin and clopidogrel in patients receiving coronary stenting.

DATA SOURCES:

Relevant information was identified through a search of MEDLINE (1966-November 2011), International Pharmaceutical Abstracts (1960-2011), and Cochrane Databases (publications archived until November 2011) using the terms cilostazol, percutaneous coronary intervention, triple therapy, and antiplatelet agents.

STUDY SELECTION AND DATA EXTRACTION:

English-language prospective and retrospective studies, including registry data in adults, were eligible for inclusion if triple therapy with cilostazol was compared with DAT with aspirin and clopidogrel in patients undergoing percutaneous coronary intervention (PCI) with stenting. Article bibliographies were also reviewed.

DATA SYNTHESIS:

Cilostazol uniquely possesses antiproliferative properties in addition to its antiplatelet effects. Several prospective and retrospective clinical trials evaluated it as a third agent in standard antiplatelet regimens after PCI with both bare metal and drug-eluting stents. Both angiographic and clinical outcomes, including major adverse cardiac events (MACEs), have been improved with the addition of cilostazol to DAT in most trials, without increasing bleeding risk. Higher-risk patients, such as elderly individuals and patients with diabetes, long lesions, or small vessels, seem to benefit the most from triple therapy. Patients who are poor responders to clopidogrel also appear to benefit from the addition of cilostazol by improving platelet reactivity with standard DAT.

CONCLUSIONS:

Triple therapy with cilostazol has been shown to reduce MACEs by providing increased inhibition of platelet aggregation and reducing the rates of in-stent thrombosis compared to DAT without increasing the risk of bleeding complications. Further studies are needed to identify proper patient selection based on risk factors for the addition of cilostazol. Additionally, studies comparing cilostazol with newer antiplatelet therapies, such as prasugrel and ticagrelor, are needed.

Loading effect of 200 mg cilostazol on platelet inhibition in patients undergoing percutaneous coronary intervention

To date, most studies conducted on cilostazol have examined its effects as an agent of maintenance-dose therapy, but its loading effects on platelet inhibition have never been reported. This study aimed to determine the loading effects of 200 mg cilostazol in addition to aspirin and clopidogrel on platelet inhibition in patients undergoing percutaneous coronary intervention.Sixty consecutive patients undergoing coronary intervention were enrolled and assigned to receive 300 mg of aspirin and clopidogrel with or without 200 mg of cilostazol. All loading doses were given at least 3 hours before percutaneous coronary intervention and followed by dual or triple maintenance-dose therapy. Platelet function tests were performed just before and at 24 hours and 30 days after percutaneous coronary intervention by light transmittance aggregometry and VerifyNow® P2Y12 assay.There were no significant differences in baseline or angiographic characteristics between the 2 groups. The results of platelet function tests revealed that the adjunctive loading dose of 200 mg of cilostazol induced more potent platelet inhibition compared to a dual regimen at each time point. Cilostazol reduced the incidence of high post-treatment platelet reactivity (HPPR).Adjunctive 200 mg cilostazol can improve platelet responsiveness to clopidogrel in the pre- and postprocedural phases, reducing the prevalence of HPPR.

Increased atherothrombotic burden in patients with diabetes mellitus and acute coronary syndrome: a review of antiplatelet therapy

Patients with diabetes mellitus presenting with acute coronary syndrome have a higher risk of cardiovascular complications and recurrent ischemic events when compared to nondiabetic counterparts. Different mechanisms including endothelial dysfunction, platelet hyperactivity, and abnormalities in coagulation and fibrinolysis have been implicated for this increased atherothrombotic risk. Platelets play an important role in atherogenesis and its thrombotic complications in diabetic patients with acute coronary syndrome. Hence, potent platelet inhibition is of paramount importance in order to optimise outcomes of diabetic patients with acute coronary syndrome. The aim of this paper is to provide an overview of the increased thrombotic burden in diabetes and acute coronary syndrome, the underlying pathophysiology focussing on endothelial and platelet abnormalities, currently available antiplatelet therapies, their benefits and limitations in diabetic patients, and to describe potential future therapeutic strategies to overcome these limitations.

Platelet reactivity in patients with chronic kidney disease receiving adjunctive cilostazol compared with a high-maintenance dose of clopidogrel: results of the effect of platelet inhibition according to clopidogrel dose in patients with chronic kidney disease (PIANO-2 CKD) randomized study

BACKGROUND

Chronic kidney disease (CKD) is a factor of low response to clopidogrel. We sought to assess the functional impact of cilostazol in CKD patients with undergoing hemodialysis.

METHODS

Seventy-four patients with CKD undergoing hemodialysis and percutaneous coronary intervention were enrolled. Patients were randomly assigned to receive clopidogrel (75 mg/d [group 1, n = 24]), high-maintenance dose of clopidogrel (150 mg/d [group 2, n = 25]), or clopidogrel (75 mg/d) with cilostazol (200 mg/d [group 3, n = 25]) for 14 days. Another 50 patients with normal renal function undergoing percutaneous coronary intervention were treated with 75 mg of clopidogrel and served as the control group. Platelet function was evaluated before and after antiplatelet therapy with light transmittance aggregometry and with VerifyNow P2Y12 assay (Accumetrics, San Diego, CA). Platelet activation markers (soluble CD40 ligand and soluble P-selectin) were also assessed.

RESULTS

The baseline platelet function measurements were similar in the 3 groups of patients; however, the CKD groups had significantly higher platelet aggregation activity compared with the control groups. The rate of high on-treatment platelet reactivity was significantly lower in group 3 than in groups 1 and 2 (10% vs 43% vs 32%, respectively; P < .05). After 14 days of antiplatelet therapy, the changes in plasma soluble CD40 ligand and soluble P-selectin levels were significantly higher in group 3 compared with groups 1 and 2 (P < .01); however, there were no significant differences in platelet function and activation markers between groups 1 and 2.

CONCLUSIONS

Adjunctive cilostazol improves platelet inhibition compared with 75 or 150 mg of clopidogrel in CKD patients undergoing hemodialysis.

Overcoming limitations of current antiplatelet drugs: a concerted effort for more profitable strategies of intervention

Platelets play a central role in the pathophysiology of atherothrombosis, an inappropriate platelet activation leading to acute ischemic complications (acute myocardial infarction, ischemic stroke). In view of this, platelets are a major target for pharmacotherapy. Presently, the main classes of antiplatelet agents approved for the use in such complications are aspirin and thienopyridines. Although antiplatelet treatment with these two types of drugs, alone or in combination, leads to a significant reduction of non-fatal myocardial infarction (-32%), non-fatal stroke (-25%), and of cardiovascular death (-17%), a residual risk persists. Newer antiplatelet agents have addressed some, but not all, these limitations. Vis-à-vis their net clinical benefit, the higher potency of some of them is associated with a rise in bleeding complications. Moreover, newer thienopyridines do not show advantages over and above the older ones as to reduction of stroke. A concerted effort that takes into consideration clinical, genetic, and laboratory information is increasingly recognized as a major direction to be pursued in the area. The well-established road signs of clinical epidemiology will provide major information to define newer potentially useful targets for platelet pharmacology.

Comparison of antiplatelet effect and tolerability of clopidogrel resinate with clopidogrel bisulfate in patients with coronary heart disease (CHD) or CHD-equivalent risks: a phase IV, prospective, double-dummy, parallel-group, 4-week noninferiority trial

BACKGROUND

Clopidogrel resinate is a resinate complex of (+)-clopidogrel optical isomer, wherein the (+)-clopidogrel isomer binds to a water-soluble cation exchange resin via sulfonic acid groups. It was approved by the Korean Food and Drug Administration on the basis of a Phase I study that demonstrated the bioequivalence of clopidogrel resinate and clopidogrel bisulfate. However, there are no available data regarding efficacy and tolerability in patients with vascular disease.

OBJECTIVE

The goal of this study was to investigate the antiplatelet efficacy and tolerability of clopidogrel resinate in patients with coronary heart disease (CHD) or CHD-equivalent risks.

METHODS

This study was a Phase IV, randomized, double-blind, double-dummy, parallel-group, noninferiority trial. We prospectively recruited patients in 10 centers between March 2008 and July 2008. Patients who had documented CHD or CHD-equivalent risks were randomly assigned to 1 of 3 groups: group A, aspirin (100 mg) + clopidogrel bisulfate placebo + clopidogrel resinate placebo; group B, aspirin (100 mg) + clopidogrel bisulfate placebo + clopidogrel resinate (75 mg); or group C, aspirin (100 mg) + clopidogrel bisulfate (75 mg) + clopidogrel resinate placebo. The primary outcome was the percent P2Y(12) inhibition after medication, assessed by using a point-of-care assay. If the 1-sided 90% upper confidence limit for the difference was less than the prespecified delta value (-5.7), clopidogrel resinate would be considered noninferior to clopidogrel bisulfate. The secondary outcome, the prevalence of adverse events (AEs) associated with study medications, was assessed at each visit by direct interview.

RESULTS

A total of 314 patients (mean [SD] age, 62.2 [9.0] years; male 63.7%; weight, 67.3 [13.6] kg [range, 45-102 kg]; all Asian) were enrolled, and 287 patients finished the study (group A, n = 97; group B, n = 90; and group C, n = 100). Eight patients took no study medications and were excluded from the tolerability and efficacy analyses. Nineteen patients discontinued the study because of protocol violation (n = 15), adverse events (n = 3), or voluntary withdrawal (n = 1) and were excluded from the efficacy analysis. There were no significant differences in baseline clinical characteristics among the groups except for the frequency of a history of CHD (group A, 85.4%; group B, 73.0%; and group C, 88.3%; P = 0.01). Patients treated with either type of clopidogrel showed significant inhibition (mean [SD]) of P2Y(12) (group A, -5.9% [15.1%]; group B, 23.4% [21.9%]; and group C, 19.5% [23.8%]; P < 0.001). Differences between clopidogrel resinate and clopidogrel bisulfate in the inhibition of P2Y(12) did not exceed the predetermined value for inferiority (P for noninferiority, 0.02; 90% CI, -0.9 to 10.3). In the tolerability analysis, there was no mortality during the study period and no significant differences between groups in the frequency of AEs and serious AEs (AEs: group A, 33.0%; group B, 26.0%; and group C, 23.3% [P = 0.27]; serious AEs: group A, 1.0%; group B, 3.0%; and group C, 1.0% [P = 0.42]). One patient in group B underwent coronary stent implantation for treatment of stable angina.

CONCLUSIONS

In this small, selected Asian patient population, differences in the platelet inhibition efficacies of clopidogrel resinate and clopidogrel bisulfate did not exceed the predetermined limits for noninferiority. The differences in tolerability between the 2 drugs did not reach statistical significance.

Significance of clopidogrel resistance related to the stent-assisted angioplasty in patients with atherosclerotic cerebrovascular disease

OBJECTIVE

To evaluate the prevalence and risk factors of clopidogrel resistance, and association between thromboembolic complications and clopidogrel resistance in patient with stent-assisted angioplasty for atherosclerotic cerebrovascular disease.

METHODS

Between September 2006 and June 2008, clopidogrel resistance test was performed on 41 patients who underwent stent-assisted angioplasty for atherosclerotic cerebrovascular disease. It was performed before drug administration and about 12 hours after drug administration (loading dose : 300 mg, maintain dose : 75 mg). Two patients were excluded, and 41 patients were included (mean : 67.59±7.10 years, age range : 41-79). Among 41 patients, 18 patients had intracranial lesions, and 23 had extracranial lesions. We evaluated the prevalence, risk factors and complications related to clopidogrel resistance.

RESULTS

Twenty-one patients (51.2%) showed clopidogrel resistance [intracranial : 10 patients (55.6%), extracranial : 11 patients (47.8%)] and no clopidogrel resistance was seen in 20 patients. Hypercholesterolemia was an indepedent risk factor of clopidogrel resistance. Stent-assisted angioplasty was technically successful in all patients, but acute in-stent thrombosis occurred in 5 patients with intracranial lesions (4 patients with clopidogrel resistance and 1 without clopidogrel resistance). Acute thrombi were completely lysed after intra-arterial infusion of abciximab.

CONCLUSION

There was relatively high prevalence of clopidogrel resistance in patients with atherosclerotic cerebrovascular disease. Hypercholesterolemia was an independent predictive factor of clopidogrel resistance. Acute in-stent thrombosis was more frequently seen in the clopidogrel resistant group. Therefore, clopidogrel resistance test should be performed to avoid thromboembolic complications related to stent-assisted angioplasty for atherosclerotic cerebrovascular disease, especially patients with hypercholeterolemia and intracranial lesion.

Oral antiplatelet therapy in diabetes mellitus and the role of prasugrel: an overview

Diabetics have a prothrombotic state that includes increased platelet reactivity. This contributes to the less favorable clinical outcomes observed in diabetics experiencing acute coronary syndromes as well as stable coronary artery disease. Many diabetics are relatively resistant to or have insufficient response to several antithrombotic agents. In the setting of percutaneous coronary intervention, hyporesponsiveness to clopidogrel is particularly common among diabetics. Several strategies have been examined to further enhance the benefits of oral antiplatelet therapy in diabetics. These include increasing the dose of clopidogrel, triple antiplatelet therapy with cilostazol, and new agents such as prasugrel. The large TRITON TIMI 38 randomized trial compared clopidogrel to prasugrel in the setting of percutaneous coronary intervention for acute coronary syndromes. The diabetic subgroup (n = 3146) experienced considerable incremental benefit with a 4.8% reduction in cardiovascular death, nonfatal myocardial infarction, and nonfatal stroke at 15-month follow-up with prasugrel treatment. Among diabetics on insulin this combined endpoint was reduced by 7.9% at 15 months. Major bleeding was not increased in the diabetic subgroup. This confirms the general hypothesis that more potent oral antiplatelet therapy can partially overcome the prothrombotic milieu and safely improve important clinical outcomes in diabetics.

Diabetes mellitus and cardiovascular prevention: the role and the limitations of currently available antiplatelet drugs

Diabetes mellitus (DM) is associated with macrovascular and microvascular complications. Platelets have a “key role” in atherogenesis and its thrombotic complications in subjects with DM. Moreover, the concomitant presence of multiple “classical” cardiovascular risk factors in diabetic subjects contributes to enhanced atherothrombotic risk. Antiplatelet agents are effective in primary and secondary prevention of arterial thrombosis (cardiovascular events, ischaemic stroke, and peripheral arterial occlusive disease). The role of chronic administration of antiplatelet drugs in primary prevention of arterial vascular events is known to be less clear than in secondary prevention, and, also in diabetic patients, the decision to give primary prophylaxis should be taken on an individual-patient basis, after a careful evaluation of the balance between the expected benefits and the risk of major bleedings. Although, currently, treatment has proven useful in reducing vascular events, diabetic patients continue to have a higher risk of adverse cardiovascular events compared with those in nondiabetic patients. This paper reviews the role of currently available antiplatelet drugs in primary and secondary prevention of vascular events in diabetic patients and the limitations of these drugs, and it discusses the role of novel and more potent antiplatelets and of new agents currently under clinical development.

Optimizing antiplatelet therapy in acute coronary syndrome and percutaneous coronary intervention

Dual antiplatelet therapy with aspirin and clopidogrel is the standard of care for patients with acute coronary syndrome (ACS) and those undergoing percutaneous coronary intervention (PCI). It is well established that inhibition of platelet aggregation reduces the risk of recurrent thrombotic events and stent thrombosis. However, some patients show a reduced antiplatelet response to standard clopidogrel loading (300 mg) and maintenance (75 mg day(-1)) doses, which has been associated with poorer patient outcomes. Pharmacodynamic and pharmacokinetic studies show that higher-than-standard clopidogrel dosing strategies facilitate more rapid platelet inhibition of a greater intensity as a result of greater plasma concentrations of the clopidogrel active metabolite. Recently completed studies suggest that in patients with ACS undergoing PCI, higher-than-standard clopidogrel dosing regimens provide greater inhibition of platelet function and improved clinical outcomes with a small but significant increase in major bleeding. Newer, more potent antiplatelet agents such as prasugrel and ticagrelor are other alternative strategies that result in more rapid, greater inhibition of platelet function and better outcomes than standard-dose clopidogrel. Whether platelet reactivity-guided therapy or genotyping for cytochrome P450 polymorphisms is useful in managing patients needs to be further defined. Most importantly, early and effective antiplatelet therapy results in the best short- and long-term outcomes for patients with ACS or those undergoing PCI.

Impact of adjunctive cilostazol therapy on platelet function profiles in patients with and without diabetes mellitus on aspirin and clopidogrel therapy

Cilostazol is a platelet inhibitor which when added to aspirin and clopidogrel has shown to reduce the risk of recurrent ischaemic events without an increase in bleeding. These clinical benefits have shown to be more pronounced in patients with diabetes mellitus (DM). However, it remains unknown whether cilostazol exerts different pharmacodynamic effects in patients with and without DM. This was a randomised, double-blind, placebo-controlled, cross-over pharmacodynamic study comparing platelet function in patients with and without DM on aspirin and clopidogrel therapy. Patients (n=111) were randomly assigned to either cilostazol 100 mg or placebo twice daily for 14 days and afterwards crossed-over treatment for another 14 days. Platelet function was performed at baseline, 14 days post-randomisation, and 14 days post-cross-over. Functional testing to assess P2Y12 signalling included flow cytometric analysis of phosphorylation status of vasodilator-stimulated phosphoprotein measured by P2Y12 reactivity index (PRI), light transmittance aggregometry and VerifyNow. Thrombin generation processes were also studied using thrombelastography. Significantly lower PRI values were observed following treatment with cilostazol compared with placebo both in DM and non-DM groups (p < 0.0001). The absolute between-treatment differences of PRI between groups was a 35.1% lower in patients with DM (p=0.039). Similar results were obtained using all other functional measures assessing P2Y12 signalling. Thrombin generation was not affected by cilostazol. Cilostazol reduces platelet reactivity both in patients with and without DM, although these pharmacodynamic effects are enhanced in patients with DM. Despite the marked platelet inhibition, cilostazol does not alter thrombin-mediated haemostatic processes, which may explain its ischaemic benefit without the increased risk of bleeding.

Clopidogrel-drug interactions

Multidrug therapy increases the risk for drug-drug interactions. Clopidogrel, a prodrug, requires hepatic cytochrome P450 (CYP) metabolic activation to produce the active metabolite that inhibits the platelet P2Y₁₂ adenosine diphosphate (ADP) receptor, decreasing platelet activation and aggregation processes. Atorvastatin, omeprazole, and several other drugs have been shown in pharmacodynamic studies to competitively inhibit CYP activation of clopidogrel, reducing clopidogrel responsiveness. Conversely, other agents increase clopidogrel responsiveness by inducing CYP activity. The clinical implications of these pharmacodynamic interactions have raised concern because many of these drugs are coadministered to patients with coronary artery disease. There are multiple challenges in proving that a pharmacodynamic drug-drug interaction is clinically significant. To date, there is no consistent evidence that clopidogrel-drug interactions impact adverse cardiovascular events. Statins and proton pump inhibitors have been shown to decrease adverse clinical event rates and should not be withheld from patients with appropriate indications for therapy because of concern about potential clopidogrel-drug interactions. Clinicians concerned about clopidogrel-drug interactions have the option of prescribing either an alternative platelet P2Y₁₂ receptor inhibitor without known drug interactions, or statin and gastro-protective agents that do not interfere with clopidogrel metabolism.

Antiplatelet drug therapy: role of pharmacodynamic and genetic testing

Antiplatelet therapy represents the cornerstone of treatment for the short- and long-term prevention of atherothrombotic disease processes, in particular in high-risk settings such as in patients with acute coronary syndrome and those undergoing percutaneous coronary intervention. Currently, dual antiplatelet therapy with aspirin and clopidogrel represents the most commonly used treatment regimen in these settings. However, a considerable number of patients continue to experience adverse outcomes, including both bleeding and recurrent ischemic events. Numerous investigations have demonstrated that this phenomenon may be, in part, attributed to the broad variability in individual response profiles to this standard antiplatelet treatment regimen, as identified by various assays of platelet function testing. In addition, recent studies have demonstrated that genetic polymorphisms may also have an important role in determining levels of platelet inhibition and may be considered as a tool to identify patients at risk of adverse events. This article provides an overview on antiplatelet drug response variability, an update on definitions, including the role of pharmacodynamic testing, underlying mechanisms – with emphasis on recent understandings on pharmacogenetics and drug–drug interactions – and current and future perspectives on individualized antiplatelet therapy.

Comparison of dual drug-eluting Cilotax stent and paclitaxel-eluting Taxus Liberte stent in native coronary artery lesions

Cilotax stent is a new type of drug-eluting stent (DES) designed to increase the antirestenotic performance of the paclitaxel-eluting stent and decrease the risk of stent thrombosis by the incorporation of cilostazol. Therefore, we investigated the safety and efficacy of Cilotax dual DESs and compared their performance to that of paclitaxel-eluting Taxus Liberte. Patients undergoing percutaneous coronary intervention for de novo coronary artery lesions at 2 centers in Korea were randomized to receive Cilotax (n = 55) or Taxus Liberte (n = 56) stents. The primary end point was in-segment late loss at 8 months. The 2 groups had similar baseline characteristics. Cilotax stent was not inferior to Taxus Liberte stent as determined by in-segment late loss (0.28 ± 0.30 vs 0.42 ± 0.45 mm, difference -0.14, 95% confidence interval -0.27 to -0.01, 1-sided p = 0.028 for noninferiority). In-stent late loss was significantly lower in the Cilotax than in the Taxus Liberte group (0.22 ± 0.31 vs 0.50 ± 0.55 mm, p = 0.002). Although in-segment restenosis rate did not differ significantly between the 2 groups (3.8% vs 10.9%, respectively, p = 0.271), in-stent restenosis rate was significantly lower in the Cilotax stent group (0% vs 10.9%, p = 0.027). There was no stent thrombosis at 8 months in either group. Rates of death, myocardial infarction, and any target lesion revascularization at 8 months were 0%, 0%, and 1.9%, respectively, in the Cilotax group and 1.8%, 0% and 3.6%, respectively, in the Taxus Liberte group. In conclusion, the Cilotax stent was safe and effective in decreasing late loss, indicating that this stent represents a promising new type of DES system.