Ticlopidine，Dipyridamoleの血小板機能に及ぼす影響—人工弁置換術後における比較検討

Evaluation of antiplatelet drugs on platelet functions: Comparison between ticlopidine and dipyridamole after prosthetic valve replacement

　心臓外科領域において，人工弁置換術後の合併症としてもっとも重要なものは血栓塞栓症であり，その予防は術後早期から遠隔期にいたるまできわめて重要な患者管理となっている^1）。この抗血栓療法に対して，ビタミンK拮抗物質であるwarfarinの投与は広く各施設において行われているが，血栓形成のメカニズムが究明されるにつれて，血栓形成においては血小板の関与がきわめて大きいことが示されるようになった。すなわち，人工弁周辺における血栓形成はまず血小板の粘着凝集により始まることが考えられ^2,3），抗血小板薬を投与することの必要性も報告されるようになったが^4,5），血小板機能を抑制する薬剤の種類は多く，その作用機序も薬剤によって異なり，効果判定については一定していない。

　今回，抗血小板薬としてticlopidineとdipyridamoleを取り上げ，人工弁置換術後早期と遠隔期における血小板機能に及ぼす影響について比較検討したので報告する。

　We examined the efficacy of antiplatelet drugs after prosthetic valve replacement.

　As an early postoperative group (group E), 49 patients were divided into four groups. In group A only warfarin was given. In group B warfarin and dipyridamole 300 mg/day, in group C warfarin and ticlopidine 300 mg/day, in group D warfarin and ticlopidine 600 mg/day were administered respectively. As a late postoperative group (group L), 45 patients with prosthetic valves were divided into two groups. In group I dipyridamole 300 mg/day in group II ticlopidine 300 mg/day were administered. Both group I and II received warfarin. In group E platelet counts and platelet aggregability were examined to 22 POD. In group L starting two years after valve replacement, platelet counts were examined eight times by three-month intervals, and platelet aggregability, platelet adhesiveness were investigated 36 months in group I and 27 months in group II postoperatively.

　Results are the following. 1) Neither ticlopidine nor dipyridamole had any effects on the platelet counts through the postoperative period. 2) In the early postoperative period, the administration of antiplatelet drugs to groups B, C, and D suppressed platelet aggregability more than group A. 3) Ticlopidine (groups C and II) reduced ADP and collagen aggregabilities compared with dipyridamole (group B and I) both in the early and late postoperative period. 4) Ticlopidine 300 mg/day (group C) and ticlopidine 600 mg/day (group D) had no difference in ADP and Collagen aggregabilities. 5) No significant difference was shown between dipyridamole (group I) and ticlopidine (group II) in platelet adhesiveness.

　It was concluded that ticlopidine inhibited platelet aggregability more effectively than dipyridamole both in short and long term administration after prosthetic valve replacement.