The present invention relates to a novel antiplatelet agent and a novel compound as the active ingredient of the same. The present invention provides an antiplatelet agent, comprising as the active ingredient a compound of formula I:wherein X is N or CR1d Xb1to Xb5are the same or different and represent nitrogen or carbon R1ato R1dare the same or different and represents hydrogen atom, optionally substituted alkyl, optionally substituted alkoxy, optionally substituted alkylthio, alkenyl, cycloalkyl, halogen, cyano, hydrogen group, or amino group optionally substituted by one or two alkyl R2is optionally substituted aryl or optionally substituted heteroaryl R3is optionally substituted aryl or optionally substituted heteroaryl or a pharmacologically acceptable salt thereof.本發明乃新穎抗血小板藥及作為其有效成分之新穎化合物有關者。本發明提供以下列式I所示化合物或其藥理學上容許之鹽作為有效成分之抗血小板藥:(上式中,X示N或CR1d,Xb1至Xb5可為相同或不同,示氮或碳原子,R1a至R1d可為相同或不同,示氫原子、可具有取代基之烷基、可具有取代基之烷氧基、可具有取代基之烷硫基、烯基、環烷基、鹵素、氰基、羥基、或可為1或2個烷基取代之胺基,R2示可具有取代基之芳基或可具有取代基之雜芳基,R3示可具有取代基之芳基或可具有取代基之雜芳基。)
