OPTIMAL PRETREATMENT TIMING FOR HIGH LOAD DOSING (600 MG) OF CLOPIDOGREL BEFORE PLANNED PERCUTANEOUS CORONARY INTERVENTION FOR MAXIMAL ANTIPLATELET EFFECTIVENESS

Background The optimal timing for 600 mg clopidogrel pre-treatment before planned PCI in patients with stable coronary artery disease has never been tested in a randomized trial.
Methods The time course of platelet inhibition was investigated in 105 patients pre-treated with clopidogrel ≥ 6h before the planned procedure. Flow cytometric analysis of the vasodilator stimulated phosphoprotein (VASP) phosphorylation state was done and a Platelet Reactivity Index (PRI) was calculated prior to treatment (baseline) and at 12, 28, 36, 60, 84 and 108 hours after the clopidogrel loading dose administration.
Results The maximal inhibition of platelet activation was seen at 28 h post administration (PRI mean 36 ± 23%), and 2/3 of patients had PRI value < 50%. At 12 hours 47% of patients had PRI value ≥ 50% (mean 45 ± 21%). 600 mg of clopidogrel significantly suppressed platelet activation for 4 days. A correlation was between baseline PRI and its values by 28 hours (rS = 0.48, p < 0.001), between 12 h – 28 h the correlation was strong (rS = 0.77, p < 0.001).
Conclusion The time curve of clopidogrel efficacy was dependent on baseline platelet reactivity. Among stable CAD patients, pre-treatment with 600 mg of clopidogrel resulted in maximal antiplatelet efficacy one day after drug administration.