Comparative effect on platelet function of a fixed-dose aspirin and clopidogrel combination versus separate formulations in patients with coronary artery disease: A phase IV, multicenter, prospective, 4-week non-inferiority trial

BACKGROUND/OBJECTIVES

The effect of aspirin and clopidogrel in a fixed-dose combination (FDC) on platelet function was compared with separate formulations in patients that had undergone percutaneous coronary intervention (PCI) with drug-eluting stent (DES).

METHODS

This was a phase IV, prospective, multicenter, single-arm, non-inferiority study. Patients that had taken aspirin 100 mg and clopidogrel 75 mg once daily as separate formulations for >6 months after PCI with DES were enrolled, and then switched to an aspirin/clopidogrel FDC once-daily for 4 weeks. Platelet reactivity was determined using the VerifyNow® P2Y12 assay at baseline (immediately prior to switching) and 4 weeks later.

RESULTS

A total of 648 patients (the full-analysis population; age, 63.6±9.0 years; male, 76.5%) finished the study, and 565 (the per-protocol population) completed without protocol violations. In the per-protocol population, the % inhibitions of P2Y12 and ARU were not significantly different between baseline and after 4 weeks of FDC treatment (29.2±20.0% to 29.0±19.9%, P=0.708; 445.1±69.2 to 446.2±63.0, P=0.799, respectively) and the difference in P2Y12 inhibition observed did not exceed the predetermined limit of non-inferiority (95% CI, -0.9 to 1.3). In the full-analysis population, the % inhibitions of P2Y12, PRU, and ARU were not significantly changed after 4 weeks of FDC treatment.

CONCLUSIONS

This study demonstrates that the efficacy of platelet inhibition by an aspirin/clopidogrel FDC was not inferior to that of separate aspirin and clopidogrel formulations in patients that had undergone PCI with DES.

Lack of association between low density lipoprotein particle size and on-treatment platelet reactivity in patients with coronary artery disease

BACKGROUND AND OBJECTIVES

Small dense low density lipoproteins (sd-LDL) are a risk factor for coronary artery disease and are known to stimulate platelet function in vitro. This study aimed to evaluate whether high proportion of sd-LDL is associated with high on-treatment platelet reactivity (HOPR).

SUBJECTS AND METHODS

From January 2009 to March 2010, 439 subjects (mean age: 64.3±9.7, Male : Female=306 : 133) were enrolled from the low density LIPOProtein-cholesterol Size measurement Registry with coronary artery disease, who had undergone elective percutaneous coronary intervention and measured both LDL particle size and on-treatment platelet reactivity (OPR). Mean LDL particle size was measured by gradient gel electrophoresis (Quantimetrix, Lipoprint™) and OPR by the VerifyNow™ system (aspirin and P2Y12).

RESULTS

Between pattern A (large, buoyant LDL dominant) and B (sd-LDL dominant) population, there were no significant difference in OPR to aspirin (441.3±71.9 vs. 434.07±63.45 aspirin reaction units, p=0.351) or clopidogrel (237.9±87.3 vs. 244.9±80.7 P2Y12 reaction units, p=0.465). There was no difference in LDL particle size between patients with HOPR compared with non-HOPR patients (aspirin: 26.8±0.5 vs. 26.7±0.6 nm, p=0.078, clopidogrel: 26.7±0.6 vs. 26.8±0.5 nm, p=0.857). Pearson's correlation coefficients between LDL particle size and platelet reactivity were not statistically significant (aspirin assay: r=0.080, p=0.098, P2Y12 assay: r=-0.027, p=0.568).

CONCLUSION

There was no significant association between LDL particle size and OPR in patients with coronary artery disease.

A comparison of clopidogrel responsiveness in patients with versus without chronic renal failure

We sought to compare the platelet responsiveness to clopidogrel between patients with chronic renal failure and those with normal renal function. We conducted a prospective, randomized, open-label, single-center trial. A total of 23 patients with normal renal function received a usual daily dose of 75 mg of clopidogrel (group I, 61 +/- 7 years). Also, 36 patients with chronic renal failure (60 +/- 5 years) were divided into 2 groups according to their daily dose of clopidogrel: a daily dose of 75 mg of clopidogrel for 30 days (group II, n = 18) or a daily dose of 150 mg (group III, n = 18). The primary efficacy variables among the study groups using the VerifyNow P2Y12 assay were the P2Y12 reaction unit value and the percentage of inhibition. A significant difference was found in the P2Y12 reaction unit value among the 3 groups (239 +/- 87 in group I, 308 +/- 70 in group II, 302 +/- 81 in group III (p = 0.013) and in the percentage of inhibition (35 +/- 20 in group I, 21 +/- 16 in group II, 23 +/- 14 in group III, p = 0.026). No significant difference was found in the P2Y12 reaction units or percentage of inhibition between groups II and III. In conclusion, platelet responsiveness to clopidogrel decreased more in patients with chronic renal failure than in those with normal renal function, and this decreased platelet responsiveness to clopidogrel was not improved by an increase in the clopidogrel dosage.

Acute and subacute stent thrombosis in a patient with clopidogrel resistance: a case report

Drug-eluting stents (DES) are considered the treatment of choice for most patients with obstructive coronary artery disease when percutaneous intervention (PCI) is feasible. However, stent thrombosis seems to occur more frequently with DES and occasionally is associated with resistance to anti-platelet drugs. We have experienced a case of recurrent stent thrombosis in a patient with clopidogrel resistance. A 63-year-old female patient suffered from acute myocardial infarction and underwent successful PCI of the left anterior descending coronary artery (LAD) with two DESs. She was found to be hyporesponsive to clopidogrel and was treated with triple anti-platelet therapy (aspirin 100 mg, clopidogrel 75 mg, and cilostazol 200 mg daily). Three days after discharge, she developed chest pain and was again taken to the cardiac catheterization laboratory, where coronary angiography (CAG) showed total occlusion of the mid-LAD where the stent had been placed. After intravenous administration of a glycoprotein IIb/IIIa inhibitor, balloon angioplasty was performed, resulting in Thrombolysis In Myocardial Infarction (TIMI) III antegrade flow. The next day, however, she complained of severe chest pain, and the electrocardiogram showed marked ST-segment elevation in V1-V6, I, and aVL with complete right bundle branch block. Emergent CAG revealed total occlusion of the proximal LAD due to stent thrombosis. She was successfully treated with balloon angioplasty and was discharged with triple anti-platelet therapy.