ε-Aminocaproic acid (EACA) and tranexamic acid (TA) are synthetic lysine analogs that inhibit plasminogen and/or plasmin-mediated Fibrinolysis. The efficacy of TA is ten times that of EACA. The anti-fibrinolytic ability of lysine analogues is understood by studying preventive prevention of blood loss and reduction of bleeding during cardiac surgery and cardiopulmonary bypass surgery. A recent meta-analysis of 12 randomized trials in patients undergoing cardiac surgery showed that TA reduced the proportion of patients receiving allogeneic red blood cell transfusions. In the same meta-analysis, only three studies (118 patients) showed that EACA was appropriate and the relative comparison was not significant. Unfortunately, there are only a few prospective studies analyzing data on the safety of the use of these agents. In ISPOT's meta-analysis of 12 cardiac trials, no increase in myocardial infarction was found, but these were retrospective analyzes that were not specifically designed for safety. Although judging from the experimental data of randomized control groups, EACA is quite limited. A combined analysis of four cardiac surgical procedures (total*** 548 patients) showed a significant increase in myocardial infarction (OR, 2.5; 95CI, 1.06-5.86; p=0.035). In noncardiac surgery, three randomized controlled trials evaluated TA in orthopedic surgery. All showed a significant reduction in transfusion requirements and none demonstrated any increase in deep vein thrombosis (DVT) or pulmonary thrombus. The ratio was ***97 people in the TA group, 6 people (6.2) developed thrombosis, ***94 people in the placebo group, 9 people (9.6) developed thrombosis (OR, 0.71; 95CI, 0.26--1.96; p=0.51) . Three trials of prophylactic TA to reduce blood loss in patients undergoing liver transplantation found no thrombotic complications in either the TA group or the control group. Although thrombosis of major blood vessels is common in patients with liver disease, because the fibrinolytic state is usually self-limiting in liver transplant patients, there is still a view that EACA may exaggerate this tendency. Kang and colleagues gave EACA to 20 patients who had undergone liver transplantation and observed no thrombosis, compared with a control rate of 3 out of 77 (3.9). Munoz and colleagues conducted a meta-analysis of 52 randomized clinical trials published from 1985 to 1998, including the use of EACA (n = 9) and aprotinin (n = 46) during cardiac surgery. Raw outcomes included whole blood loss, red blood cell transfusion rate and total volume, repeat probing rate, stroke rate, myocardial infarction, and mortality. Unfortunately, the results of EACA were five times greater than those of aprotinin, and most EACA investigators were primary CABG patients who reported minimal bleeding. The authors report significant reductions following all postoperative infusions of EACA (a decrease of 61 compared with placebo) and high-dose aprotinin (a decrease of 62). In these studies, data from patients in the aprotinin-treated group included a series of repeat sternotomies, valve surgeries, and more complex patients, whereas the EACA-treated group consisted of a small number of primary CABG surgery patients. Although both drugs reduce reprobing rates to a similar extent, aprotinin must be used at higher doses. Finally, most of the methods used to study the incidence of side effects in EACA-treated patients are not consistent with the rigorous evaluation methods used in FDA-sponsored clinical trials to evaluate the safety of aprotinin.