Low molecular weight heparin (LMWH) is a type of anticoagulant drugs used to:
- prevent and treat venous thromboembolism
- treatment of myocardial infarction (heart attack)
- treatment of superficial phlebitis
- prevention of stroke in patients with atrial fibrillation
Heparin is a naturally occurring polysaccharide which counteracts coagulation i.e. works against the process which leads to thrombosis. Low molecular weight heparins are manufactured usually from heparin through depolymerization process. The best known low molecular weight heparins are FRAXIPARINE (nadroparin), Clexane (enoxaparin) and Fragmin (dalteparin).
They are used in the form of subcutaneous injection. Your doctor can explain you how to applicate the heparin injection yourself. Patients are usually able to do it themselves with the factory prepared a syringe with a metered dose, much like a diabetic insulin. They are applied mostly to the skin of the abdomen or thighs. If you are longer on low molecular heparin therapy, bruises can form after application as a result of its own anticoagulant effect.
Unlike warfarin, the low molecular weight heparin effect start already a short time after application and lasts about 12-24h. It is used when is needed immediate anticoagulant effect which is relatively short lasting. Low molecular weight heparin is generally used for transferring a patient on warfarin, and vice versa. The effect of warfarin starts after a few days of use, and therefore the simultaneous use of LMWH helps to bridge this period.
Treatment usually does not require frequent laboratory control, and there is a lower risk of bleeding. Caution in dosing is necessary, particularly in patients with impaired renal function.
Low molecular weight heparin in pregnancy
Although warfarin is the anticoagulant of choice in the nonpregnant state, it crosses the placenta and has been linked to structural birth defects known as “warfarin embryopathy.” Heparins (unfractionated and low molecular weight) are the preferred drugs for management of venous thromboembolism in pregnancy. Both are large molecular weight molecules and neither crosses the placenta (i). In contrast to the coumarin derivatives (Wafrarin, Coumadin), heparins do not cause teratogene-sis or toxic fetal effects.