Association between CYP2C19 genotype and the additional effect of cilostazol to clopidogrel resistance in neuroendovascular therapy

We investigated the association between CYP2C19 genotype and additional effect of cilostazol on clopidogrel resistance (CR) in neuroendovascular therapy. Between January 2012 and January 2016, 447 consecutive patients were administered with 75-mg cilostazol/day. The VerifyNow System was used for evaluating P2Y12 reaction units (PRU) > 230 and/or percentage inhibition of platelet function (% Inhibition) ≤ 20 as CR. Among 158 patients with CR, 31 were administered with additional 100- or 200-mg cilostazol/day and their platelet function was evaluated. According to CYP2C19 genotypes revealed using the Spartan RX and DNeasy Blood & Tissue Kit, patients were classified into three phenotypic groups: extensive metabolizer (EM, three patients), intermediate metabolizer (IM, 12 patients), and poor metabolizer (PM, 16 patients). Administration of additional cilostazol decreased PRU (EM group: 160.7 ± 85.2 after vs 278.3 ± 40.1 before, P = 0.15; IM group: 205.6 ± 74.0 vs 254.3 ± 35.0, P = 0.02; and PM group: 227.8 ± 52.2 vs 282.1 ± 30.4, P = 0.003), and increased % Inhibition (EM group: 40.0 ± 27.9 vs 9.3 ± 3.8, P = 0.25; IM group: 31.4 ± 18.0 vs 11.8 ± 8.2, P = 0.001; and PM group: 24.6 ± 15.0 vs 10.4 ± 9.3, P = 0.001). However, the rate of normalized-clopidogrel response, thromboembolic lesions, and bleeding complications were not significantly different among the three groups. Thus, the addition of cilostazol was effective on CR in terms of PRU, % Inhibition, rate of change of normalized-clopidogrel response, thromboembolic events, and bleeding complications irrespective of phenotype.