Low molecular weight heparin

Low-molecular-weight heparin (LMWH) is a class of anticoagulant medications. These drugs are used for treating deep vein thrombosis, pulmonary embolism when it is located in the veins, or heart attacks and strokes when located in the arteries.

Heparin is a naturally occurring polysaccharide that inhibits coagulation, the process that leads to thrombosis. Natural heparin consists of molecular chains of varying lengths, or molecular weights. Chains of varying molecular weights, from 5000 to over 40,000 Daltons, make up polydisperse pharmaceutical-grade heparin. LMWHs, in contrast, consist of only short chains of polysaccharide. LMWHs are defined as heparin salts having an average molecular weight of less than 8000 Da and for which at least 60% of all chains have a molecular weight less than 8000 Da. These are obtained by various methods of fractionation or depolymerisation of polymeric heparin.

Heparin derived from natural sources, mainly porcine intestine or bovine lung, can be administered therapeutically to prevent thrombosis. However, the effects of natural, or unfractionated heparin are more unpredictable than LMWH.

Lupus anticoagulant

Lupus anticoagulant (also known as lupus antibody, LA, LAC, or lupus inhibitors) is an immunoglobulin that binds to phospholipids and proteins associated with the cell membrane. Lupus anticoagulant is a misnomer, as it is actually a prothrombotic agent. That is, Lupus anticoagulant antibodies in living systems cause an increase in inappropriate blood clotting. Their name derives from their properties in vitro, since in laboratory tests, these antibodies cause an increase in aPTT. It is speculated that the antibodies interfere with phospholipids utilized to induce in vitro coagulation. In vivo, it is thought to interact with platelet membrane phospholipids, increasing adhesion and aggregation of platelets; thus its in vivo prothrombotic characteristics.