(1) Ordinary (standard) heparin is extracted from pig or sheep mucous membrane with an average molecular weight of 15000, which is quite stable.

　　(2) The molecular weight less than 6000 is usually called low molecular weight heparin. Compared with ordinary heparin, low molecular weight heparin has a longer half-life and better antithrombotic effect, but has a weaker anticoagulant bleeding tendency and has a tendency to replace ordinary heparin. Clinical commonly used in recent years are: da heparin sodium, enoxaparin sodium, low molecular heparin calcium.

　　(3) There are other heparin preparations with low anticoagulant activity, modified heparin and heparin-like substances that are currently under in-depth study. These drugs are characterized by low anticoagulant activity, high antithrombotic activity, long acting time and less bleeding effect, which have great development prospects.

　　Heparin sodium is a sodium salt of glucosamine sulfate extracted from pig intestinal mucosa. It belongs to mucosaccharide and plays an anticoagulant role by activating antithrombin ⅲ (AT- ⅲ). It has an effect on all three stages of the coagulation process, has anticoagulant effect in vivo and in vitro, and can prolong the coagulation time, prothrombin time and thrombin time.

　　The effect of heparin calcium and heparin sodium is similar, but this product does not reduce the calcium glia of intercellular capillaries or change the permeability of blood vessels after subcutaneous injection, and basically overcomes the side effect of heparin sodium subcutaneous injection which is easy to cause bleeding. This product also has obvious anti renin and anti aldosterone activity.