Approximately 100000 people suffer cardiopulmonary arrest in Japan every year, and the aging of society means that this number is expected to increase. Worldwide, approximately 100 million develop cardiac arrest annually, making it an international issue. Although survival has improved thanks to advances in cardiopulmonary resuscitation, there is a high rate of postresuscitation encephalopathy after the return of spontaneous circulation, and the proportion of patients who can return to normal life is extremely low. Treatment for postresuscitation encephalopathy is long term, and if sequelae persist then nursing care is required, causing immeasurable economic burdens as a result of ballooning medical costs. As at present there is no drug treatment to improve postresuscitation encephalopathy as a complication of cardiopulmonary arrest, the development of novel drug treatments is desirable. In recent years, new efficacy for existing drugs used in the clinical setting has been discovered, and drug repositioning has been proposed as a strategy for developing those drugs as therapeutic agents for different diseases. This review describes a large-scale database study carried out following a discovery strategy for drug repositioning with the objective of improving survival rates after cardiopulmonary arrest and discusses future repositioning prospects.