Comparison of 600 mg Versus 300 mg Clopidogrel Loading Dose for Patients With Ischemic Heart Disease: A Meta-Analysis of Randomized Controlled Trials

Introduction: While a 600 mg loading dose (LD) of clopidogrel has demonstrated superior inhibition of platelet function compared to 300 mg LD, the clinical evidence supporting this superiority is limited. The debate centers on whether higher clopidogrel LD regimen in percutaneous coronary intervention (PCI) outperforms the standard 300 mg LD, with potential benefits being more pronounced in higher-risk patients. Balancing enhanced platelet inhibition to reduce ischemic events against the associated risk of increased bleeding remains a critical consideration in determining the optimal loading dose of clopidogrel for patients with ischemic heart disease. Methods: A systematic literature search for randomized clinical trials (RCTs) was performed comparing 600 mg with 300 mg LD of clopidogrel using PubMed, MEDLINE, Embase, Cochrane, Clinicaltrials.gov and HerdinPH. Studies included those between 2010 and 2023 involving human subjects. The primary efficacy endpoint was a 1-month rate of major adverse cardiac event (MACE) and the primary safety outcome was bleeding adverse effects. Results: Nine RCTs involving 29,827 patients were included in the efficacy analysis. Mean duration of follow-up was 30 days. Only eight studies were eligible for safety analysis. Compared with standard LD clopidogrel, high LD significantly reduced the incidence of overall MACE (OR: 0.82, 95% CI: 0.74-0.91, p = 0.0002), nonfatal myocardial infarction (OR: 0.56; 95% CI: 0.32-0.99, p = 0.15) and target vessel revascularization (OR: 0.63; 95% CI: 0.41-0.95, p = 0.03), without significant difference in terms of cardiac death (OR: 0.89; 95% CI: 0.76-1.04, p = 0.15) and stroke (OR: 0.92; 95% CI: 0.67-1.26, p = 0.61). However, major bleeding risk was higher in the 600 mg LD (1.9%; 261/13288) compared with 300 mg LD (2.4%; 328/13242) [OR: 1.27; 95% CI: 1.08-1.49, p = 0.005] without significant difference in minor bleeding (OR: 1.05; 95% CI: 0.94-1.17, p = 0.35). Conclusion: The administration of 600 mg clopidogrel LD reduces the overall risk of MACE with associated increased risk of major bleeding.