Low molecular weight heparins (LMWHs) (derivatives of heparin)and heparin are drugs of choice when rapid anticoagulation is required.Because of the heterogeneous pharmacokinetics of heparin and its sidepotentially severe effects. Low molecular weight heparins have replacedunfractionated heparin in various medical and surgical settings such asprevention of venous thromboembolism, for the treatment of venousthrombosis, for the treatment of acute pulmonary embolism and for theearly treatment of patients with unstable angina.