Heparin. An important drug enters its seventh decade

Heparin is the drug most widely used to prevent blood from clotting. Approximately 33 metric tons, representing 500 million doses, of heparin are used worldwide each year. The use and applications of heparin continue to increase despite its structural complexity, multiple activities and many side-effects. New heparins having high therapeutic indices and increased specificities, are currently being developed. The 21st century assures a rising demand for heparinised biomaterials with the introduction of new extracorporeal devices and implanted artificial organs. This article discusses the history of heparin, its biosynthesis and preparation, its structure and biological activities, and future direction.