Direct thrombin inhibitors
Direct factor Xa inhibitors ("xabans")
Rivaroxaban and apixaban are the first drugs in this group of new oral anticoagulants (NOACs). As their group name already suggests, they act by directly inhibiting clotting factor Xa in a reversible and selective manner. Due to this mechanism both the intrinsic and the extrinsic coagulation pathways are interrupted.
Rivaroxaban and apixaban are both registered for the prevention of thromboembolic events in patients who received hip or knee surgery. In addition, rivaroxaban may be used for the prevention of stroke and systemic embolism in patients with atrial fibrillation and for the treatment and prevention of deep venous thrombosis, and the prevention of pulmonary embolism.
The most common adverse effects of direct factor Xa inhibitors
are anaemia, dizziness, headache, syncope (fainting), bleeding in various parts of the body, tachycardia (rapid heartbeat), hypotension (low blood pressure), haematoma (collection of blood under the skin), and gastrointestinal disorders.
Monitoring of the coagulation with INR in patients treated with these anticoagulants is not necessary as is the case with the vitamin K antagonists. This might seem an advantage for the patient, however compliance can not be monitored clearly anymore.
Rivaroxaban has high oral bioavailability and a rapid, predictable, dose-related action. Its half-life is about 5–9 hours. Rivaroxaban is substrate of CYP3A4 and is mainly excreted via the kidneys. Apixaban has a bioavailability of 50% and is almost completely metabolised in the liver by CYP3A4.