Abstract: Drug compositions containing a substituted diamine compound represented by formula (1): Q1-Q2-r-N(R1)-Q3-N(R2)??(1) wherein Q3 represents the following group wherein Q5 represents an alkylene group having 4 carbon atoms, R3 represents a hydrogen atom, and R4 represents a 3-6 membered heterocyclic group which may be substituted; are useful for preventing and/or treating cerebral infarction, cerebral embolism, myocardial infarction, angina pectoris, pulmonary infarction, pulmonary embolism, Buerger's disease, deep venous thrombosis, disseminated intravascular coagulation syndrome, thrombus formation after artificial valve or joint replacement, thrombus formation and reocclusion after angioplasty, systemic inflammatory response syndrome (SIRS), multiple organ dysfunction syndrome (MODS), thrombus formation during extracorporeal circulation, or blood clotting upon blood drawing.