Abstract Background 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 a higher clopidogrel LD regimen in primary percutaneous coronary intervention 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. Purpose The objective of this meta-analysis is to validate current randomized trials that investigate the efficacy and safety of two clopidogrel loading regimens (600 mg vs 300 mg) in patients with ischemic heart disease treated with primary percutaneous coronary intervention. Method A systematic literature search for randomized controlled trials was performed comparing 600 mg with 300 mg LD of clopidogrel using PubMed, MEDLINE, Embase, Cochrane, Clinicaltrials.gov. and Herdin PH. Studies included those between 2010 - 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. Result Nine randomized control studies involving 29,827 patients were included in the efficacy analysis. Mean duration of follow-up was 30 days. Only 8 studies were eligible for safety analysis. Compared with standard LD clopidogrel, high LD significantly reduced 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 to 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 to 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 of clopidogrel LD reduces the overall risk of MACE with an associated increased risk of major bleeding in patients with ischemic heart disease undergoing primary percutaneous coronary intervention.MACE OUTCOMES