High-Dose Clopidogrel Loading in Percutaneous Coronary Intervention

OBJECTIVE: To review the use of a 600-mg clopidogrel loading dose in patients undergoing percutaneous coronary intervention (PCI). DATA SOURCES: Human clinical trials and platelet studies available through PubMed (1966-March 2005), bibliographies of pertinent articles, and citations supplied by the drug manufacturer were accessed. DATA SYNTHESIS: The administration of a 600-mg loading dose of clopidogrel can decrease the time required for maximum platelet inhibition to 2 hours compared with > or =6 hours achieved with 300 mg. This higher loading dose has been investigated in multiple platelet studies and one observational report. Several randomized controlled trials have used a 600-mg loading dose; however, these studies were not designed to evaluate the efficacy and safety of this loading regimen. To date, only one randomized trial has compared the 600-mg loading dose with a 300-mg loading dose. CONCLUSIONS: When compared with a conventional loading regimen of 300 mg in lower-risk patients, pretreatment with clopidogrel 600 mg was shown to be more effective in reducing periprocedural events and demonstrated similar safety. Studies are needed to clarify the use of a 600-mg loading dose in higher-risk patients, with concomitant glycoprotein IIb/IIIa receptor antagonism, or when administration is delayed until immediately before or after PCI.