What are the differences between unfractionated heparin and low molecular weight heparin?
Unfractionated heparin (UFH) is a naturally occurring polysaccharide that is derived from porcine and bovine mucosal tissues, whereas low molecular weight heparin (LMWH) is a chemically modified derivative of UFH. UFH is a large molecule with a molecular weight of around 20,000 Da, whereas LMWHs have a molecular weight of around 5,000 Da. LMWH has a more predictable anticoagulant response than UFH, since it is composed of smaller, more homogenous molecules. LMWH requires less frequent dosing than UFH and is associated with lower risk of heparin-induced thrombocytopenia. LMWH also has a longer half-life than UFH and can be administered subcutaneously. Finally, LMWHs have been found to be more effective than UFH in the prevention of venous thromboembolism in patients undergoing major orthopedic surgery. 