A double-blind, randomized study on platelet aggregation in patients treated with a daily dose of 150 or 75 mg of clopidogrel for 30 days

AIMS: We sought to test whether an increase in the clopidogrel maintenance dose results in increased inhibition of platelet aggregation. METHODS AND RESULTS: Sixty patients after pre-treatment with 600 mg of clopidogrel and within 12 h after successful PCI were included in this trial. They were allocated to receive one of two clopidogrel daily maintenance doses (75 or 150 mg) for 30 days in a double-blind randomized manner. Platelet function was evaluated 30 days after the intervention with optical aggregometry and with a new point-of-care test (VerifyNowtrade mark P2Y12 assay). Maximal 5 microM ADP-induced platelet aggregation 30 days after PCI in the group treated with 150 mg/day clopidogrel (45.1 +/- 20.9%) was significantly lower than in the group treated with 75 mg/day (65.3 +/- 12.1%; P < 0.001). The VerifyNowtrade mark P2Y12 assay also indicated a higher degree of platelet function inhibition in the group treated with 150 mg/day (60.0 +/- 72.0 P2Y12 Reaction Units) than in the group treated with 75 mg/day (117.0 +/- 64.3 P2Y12 Reaction Units; P = 0.004). CONCLUSION: Administration of a 150 mg oral maintenance dose of clopidogrel results in more intense inhibition of platelet aggregation than administration of the currently recommended 75 mg maintenance dose.