Low molecular weight heparin
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In medicine, low molecular weight heparin (LMWH) is a class of medication used as an anticoagulant in diseases that feature thrombosis, as well as for prophylaxis in situations that lead to a high risk of thrombosis.
Heparin is a naturally-occurring polysaccharide that inhibits coagulation, the process whereby thrombosis occurs. In nature, heparin consists of molecular chains of varying lengths, or molecular weights. Heparin derived from natural sources (including intestine) can be administered therapeutically to prevent thrombosis (see anticoagulation). However, the effects of natural, or unfractionated, heparin can be difficult to predict. After a standard dose of unfractionated heparin, coagulation parameters must be monitored very closely to prevent over- or under-anticoagulation.
Low molecular weight heparin, in contrast, consists of only short chains of polysaccharide selected from unfractionated heparin. This means that a given dose of low-molecular weight heparin will be absorbed more predictably, leading to overall more predictable anticoagulation. It is also more selective for thrombin and is a comparatively weak inhibitor of factor Xa.
Its differences with unfractioned heparin are:
- No need for monitoring of the APTT coagulation parameter
- Possibly a smaller risk of bleeding
- Smaller risk of osteoporosis in long-time use
- Smaller risk of heparin-induced thrombocytopenia, a feared side-effect of heparin.
When the degree of anticoagulation must be monitored closely, such as in patients with extremes of weight or kidney function, an anti-factor Xa activity may be followed.
Makes of LMWHs include:
- Dalteparin (Fragmin®)
- Enoxaparin (Clexane® and Lovenox®)
- Nadroparin (Fraxiparin® and Fraxodi®)
- Tinzaparin
- Several othersnn:Lågmolekylært heparin