Apixaban

Apixaban is an anticoagulant medication used to treat and prevent blood clots and to prevent strokes in people with atrial fibrillation. In particular, it is used to prevent blood clots after hip or knee replacement surgery and in people who have been previously diagnosed with blood clots. It is preferred as an alternative to warfarin, it does not require monitoring by blood tests, can be taken orally, and has a more favorable side effect profile. It is taken by mouth.

In 2007, Pfizer and Bristol-Myers Squibb began developing apixaban as an anticoagulant. Apixaban was approved for medical use in the European Union in May 2011 and in the United States in December 2012. It is on the World Health Organization's list of essential medicines.

Pharmacodynamics

Factor X is a coagulation factor and an important component in the human blood coagulation cascade. In its activated form (factor Xa), it catalyzes the formation of thrombin from prothrombin, which is responsible for blood clotting. Apixaban selectively inhibits factor Xa in its free and bound forms, thereby stopping blood clotting. Apixaban also inhibits prothrominase. These effects prevent thrombus formation.

Pharmacokinetics

Apixaban is approximately 50% bioavailable. Protein binding is relatively high at 92-94%. Approximately 50% of the orally administered dose is excreted as unchanged parent compound. Apixaban metabolites account for approximately 32% of the excreted dose. Apixaban is metabolized primarily by the enzyme CYP3A4 and to a lesser extent by CYP1A2, CYP2C8, CYP2C9, CYP2C19, and CYP2J2. 56% of the orally administered dose is excreted in feces and 24.5-28.8% of the dose is excreted in urine. The elimination half-life is 12 h on average.

Drug Interactions

Concomitant use with other drugs that affect blood clotting may further increase the risk of bleeding.

These include drugs such as:

• Anticoagulants
• Heparin
• Aspirin
• Platelet aggregation inhibitors
• Selective serotonin reuptake inhibitors (SSRIs)
• Serotonin-norepinephrine reuptake inhibitors (SNRI)
• Non-steroidal anti-inflammatory drugs (NSAIDs)

Side effects

• Anemia
• Increased risk of bleeding (gastrointestinal bleeding, nosebleeds)
• Hematochezia
• Hematemesis
• Melena
• Thrombocytopenia
• Drop in blood pressure
• Nausea

Contraindications

• Hemophilia
• Severe liver diseases