Despite wide interindividual variability in response to clopidogrel, platelet P2Y₁₂ ADP receptor inhibition in Japanese patients has not been fully studied using specific methodology. This study compared platelet P2Y₁₂ ADP receptor inhibition during treatment with clopidogrel versus clopidogrel plus cilostazol in patients undergoing coronary stenting.
Forty-two patients in whom platelet function was measured within 2 months after coronary stenting were enrolled. All patients were treated with aspirin 100 or 200 mg/day, and were divided into a dual therapy group (aspirin plus clopidogrel 75 mg/day; n = 34) and a triple therapy group (aspirin plus clopidogrel 75 mg/day plus cilostazol 200 mg/day; n = 8). Vasodilator-stimulated phosphoprotein (VASP) phosphorylation analysis and 5 and 20 μmol/L-induced maximal platelet aggregation were assessed.
No differences were found in baseline characteristics except for a higher incidence of diabetes mellitus (DM) in the triple therapy group. Although there were no differences in platelet aggregation between the 2 groups, VASP index was significantly lower in the triple therapy group than in the dual therapy group (23.1 ± 15.3% versus 51.2 ± 19.9%; P = 0.001). The rate of low responsiveness to clopidogrel, defined by VASP index > 50%, was lower in the triple therapy group than in the dual therapy group (12.5% versus 55.9%; P = 0.047). Similarly, in DM patients the triple therapy group had a lower VASP index compared with the dual therapy group (23.1 ± 15.3% versus 47.0 ± 23.5%; P = 0.015).
Clopidogrel plus cilostazol is more effective in inhibiting the platelet P2Y₁₂ ADP receptor pathway than clopidogrel alone. This may be useful for reducing clopidogrel resistance in Japanese patients.