Potential mechanisms of nafamostat therapy for severe COVID-19 pneumonia with disseminated intravascular coagulation

•Antiviral treatment did not show efficacy for hypoxemia and DIC in a COVID-19 patient.•Heparin and nafamostat combination therapy showed dramatic efficacy on the illness.•Mechanisms by which nafamostat is effective for COVID-19 have been fully explained.•This would be an instructional lecture on nafamostat therapy for COVID-19 patients. Nafamostat, a serine proteinase inhibitor with various actions including antithrombin, antiplasmin, and antitrypsin effects, has been used in clinical practice to treat disseminated intravascular coagulation (DIC) and pancreatitis. This case report describes the clinical course of a patient with COVID-19 pneumonia whose severe hypoxemia, probably caused by DIC and pulmonary embolism, showed remarkable improvement with combination heparin and nafamostat therapy. In addition, beneficial mechanisms of nafamostat against COVID-19 and the necessity of attention to hyperkalemia as an adverse effect are discussed.