Anticoagulant Therapy
Anticoagulation therapy denotes the administration of an anticoagulant drug with the aim to inhibit clotting of the subject’s blood. The effect of an anticoagulant is based on the influence to the plasmatic coagulation of the subject, the influence to the plasmatic coagulation factors, to reduce or inhibit clotting activity.
Anticoagulants can be divided into:
- vitamin K antagonists
- indirect anticoagulants
- direct anticoagulants
For many years, treatment options of venous thromboembolism have been limited to unfractionated heparin or vitamin K antagonists. Recently, many other anticoagulants have been established.
Vitamin K Antagonists
These drugs belong to the group of coumarins. They suppress the vitamin K dependent synthesis of coagulation factors and thus exert an inhibitory effect on the plasmatic coagulation. The dosage form is a daily tablet intake. Regular blood sample drawing and determination of the INR value define the dose.
Indirect Anticoagulants
Heparins (glycosaminoglycans) are only administered parenterally. Their mechanism of action is based on the increase in activity of endogenous antithrombin. The anticoagulant effect is therefore dependent of the subject’s antithrombin. Depending on the molar mass, heparins are distinguished between unfractionated heparin (UFH) and low molecular weight heparin (LMWH). Routine measurement of LMWH like UFH is still under discussion. In the following exceptional cases, the determination of anti-factor Xa levels is recommended:
- renal failure
- underweight, overweight, obesity
- bleeding complications
- thrombosis despite adequate therapy
- elderly subjects
- children and neonates
The pentasaccharide fondaparinux (Arixtra®), is also an indirect factor Xa inhibitor and is prepared completely synthetically. A drug level can be obtained by using specific calibrators. Danaparoid sodium (Oragaran®), is an anticoagulant from the group of heparinoids that inhibits blood clotting similar to heparin. It accelerates the inhibitory activity of antithrombin. It consists of a mixture of glycosaminoglycans, which are obtained from animal intestinal mucosa. A drug level can be obtained by using specific calibrators.
Direct Anticoagulants
These drugs intervene directly in the coagulation cascade and inhibit directly specific clotting factors. The targets of currently approved anticoagulants are factor Xa and factor IIa (thrombin). Current research also deals with other factors of the coagulation cascade (e.g. Factor XIa, Factor XIIa and Factor XIIIa).
Factor Xa inhibitors
- Apixaban (Eliquis®)
- Rivaroxaban (Xarelto®)
- Edoxaban (Lixiana®)
Factor IIa inhibitors
- Dabigatran (Pradaxa®)
See also: DOACs