Heparin and Low-Molecular-Weight Heparin Mechanisms of Action, Pharmacokinetics, Dosing, Monitoring, Efficacy, and Safety

Heparinand its derivative, low-molecular-weight heparin (LMWH), are theanticoagulants of choice when a rapid anticoagulant effect is required, because their onset of action is immediate when administered by IVinjection. Both types of heparins are administered in lower doses forprimary prophylaxis than for treatment of venous thrombosis or acutemyocardial ischemia. Heparin has pharmacokineticlimitations 1 Rosenberg RD Lam L Correlation between structure and function of heparin. Proc Natl Acad Sci USA. 1979; 76: 1218-1222 Crossref PubMed Google Scholar not shared by LMWHs. Based on thesepharmacokinetic limitations, heparin therapy is usually restricted tothe hospital setting, where its effect can be monitored and its dosageadjusted frequently. In contrast, LMWH preparations can be administeredin either the in-hospital or out-of-hospital setting because they canbe administered subcutaneously (sc) without the need for laboratorymonitoring. When long-term anticoagulant therapy is indicated, heparinor LMWH administration is usually followed by treatment with oralanticoagulants. However, long-term out-of-hospital treatment withheparin or LMWH is used when anticoagulant therapy is indicated inpregnancy and in patients who develop recurrent venous thromboembolismwhile treated with appropriate doses of oral anticoagulants.