血液凝固是导致血栓形成症的直接原因,抗血凝药的使用,可減低血栓形成的趋势。首先应用于治疗的抗血凝药是肝素。它能延長血液凝固的时間,为目前阻止和控制栓塞性血栓形成症最常用的速效药。其唯一缺点是口服無效,必須注射給药,而且有效时間很短,只能維持几小时。因此有效的口服抗凝血药,就显得特別重要。近年来在这方面已有很多新的發現,茲將已經临床試驗証明其确具相当疗效而有代表性者分述如下: Blood coagulation is the direct cause of thrombosis, the use of anti-coagulant drugs, can reduce the tendency of thrombosis. The first anticoagulant used in the treatment of heparin. It prolongs blood clotting time and is currently the most commonly used fast-acting drug in the prevention and control of thromboembolism. Its only drawback is oral ineffective, it must be injected and administered, and the effective time is very short, only to maintain a few hours. Therefore, effective oral anticoagulants, it is particularly important. In recent years, many new discoveries have been made in this respect. The following are the typical examples of clinical trials that have proven to be quite effective: