Mode of action of unfractionated and low molecular weight Heparins on the generation of thrombin in plasma

H.C. Hemker, S. Beguin

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    Heparins, unfractionated and low molecular weight, act primarily by their scavenging of thrombin (S-type heparins). Via the feedback effect on factor VIII this has a secondary effect on prothrombin conversion in the intrinsic pathway (activated partial thromboplastin time). The anti-Xa action of a heparin will not significantly inhibit prothrombin conversion, except in the case of ultra low molecular weight heparins (P-type heparins) that have no significant antithrombin activity. These P-type heparins need, therefore, be given at high doses to have an antithrombotic effect. In platelet-rich plasma heparins retard platelet activation by lowering thrombin levels. Activated platelets neutralize up to 0.5 U/ml of unfractionated heparin, but low molecular weight heparin is much less affected.
    Original languageEnglish
    Pages (from-to)81-92
    Number of pages12
    Issue numberSuppl. 1
    Publication statusPublished - 1990

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