Heparin (including heparin sodium, heparin calcium, and low molecular weight heparin) is an anticoagulant.

　　(1) Ordinary heparin is a sodium sulfamate (calcium) extracted from the intestinal mucosa of the lungs of pigs or cattle, with an average molecular weight of about 15000 daltons.

　　(2) Small molecular fragments with small molecular weights (about 3000-7000 daltons) are usually referred to as low molecular weight heparin.

　　Heparin has achieved good results in the prevention and treatment of venous thrombosis, but it also brings many adverse reactions, such as bleeding, thrombocytopenia, anaphylaxis and so on. Compared with ordinary heparin, LMWH heparin has a longer half-life, higher bioavailability, better antithrombotic effect, fewer bleeding adverse reactions, and generally does not require laboratory monitoring.

　　Low molecular weight heparin (LMWH) is a small molecular fragment with an average molecular weight of about 5000 daltons, which is obtained by heparinase digestion, β -elimination chemical depolymerization, and nitrite lysis. There are two types: low molecular weight heparin calcium and low molecular weight heparin sodium. Low molecular weight heparin calcium in IIa was slightly stronger than low molecular weight heparin sodium, and anticoagulant factor Xa was weaker. After subcutaneous injection of low molecular weight heparin calcium, the colloid between capillary cells did not decrease, nor did vascular permeability change, and the side effect of subcutaneous injection of bleeding was small. Low molecular weight heparin calcium also has obvious anti-renin and anti-aldosterone activities, local stimulation is lighter than heparin sodium.