[Modern anticoagulation. Problems of the proven, hope for the new].

Anticoagulation is highly effective in the prevention and treatment of venous thromboembolism (VTE). Since decades, vitamin K antagonists (VKA) were the only available oral anticoagulants. Even though VKA are very effective, they have numerous practical problems: Due to their narrow therapeutic window, highly variable dose requirements and drug interactions, close monitoring is mandatory, aiming towards an INR of 2-3 for most indications. At present, new oral anticoagulants are being studied, such as the oral direct thrombin inhibitor Ximelagatran, which in trials for prevention and treatment of VTE appears at least equivalent to heparin and VKA. Heparins have to be administered parenterally, and low molecular-weight heparins have been able to overcome some of the shortcomings of standard heparins, such as limited bioavailability, variable dose response and heparin induced thrombocytopenia (HIT). Heparinoids and hirudins are alternative anticoagulants to treat HIT. With the development of synthetic pentasaccharides, such as Fondaparinux an increase in efficacy could be achieved in high-risk thromboprophylaxis.