apixaban

Apixaban is an oral anticoagulant in the direct oral anticoagulant (DOAC) class. It selectively inhibits factor Xa, a key enzyme in the coagulation cascade, which lowers thrombin generation and reduces the formation of clots. It is marketed as Eliquis and is used to reduce the risk of stroke and systemic embolism in nonvalvular atrial fibrillation, to prevent venous thromboembolism after hip or knee replacement, and to treat deep vein thrombosis (DVT) and pulmonary embolism (PE) in appropriate patients.

Mechanism and pharmacology

Apixaban acts directly and specifically on factor Xa, both in the absence and presence of clot formation, leading to decreased thrombin production. Routine laboratory monitoring is not required for dose management, but coagulation tests may be affected by tests used in special circumstances. It is absorbed orally with a bioavailability of about 50% and reaches peak concentrations in a few hours. The elimination half-life is around 12 hours in healthy individuals. Apixaban is metabolized mainly by CYP3A4 and transported by P-glycoprotein; approximately a portion is excreted renally. Doses may be adjusted or avoided with strong inhibitors or inducers of CYP3A4 and P-gp. Care is needed when combined with NSAIDs or other antiplatelet agents due to bleeding risk.

Dosing by indication

For nonvalvular atrial fibrillation, the standard dose is 5 mg twice daily. A reduction to 2.5 mg twice daily is recommended if a patient has at least two of: age 80 years or older, body weight 60 kg or less, or creatinine clearance insufficient (for example, elevated serum creatinine). For the treatment of DVT or PE, typical regimens start with 10 mg twice daily for 7 days, followed by 5 mg twice daily. For prophylaxis after hip or knee replacement, apixaban is given at 2.5 mg twice daily starting 12 to 24 hours after surgery; hip replacement typically requires 35 days of therapy, while knee replacement requires 12 days.

Safety and contraindications

Apixaban increases bleeding risk and is not recommended in patients with active major bleeding, severe hepatic impairment with coagulopathy, significant renal impairment (creatinine clearance very low), pregnancy, or lactation. It is contraindicated in patients with mechanical heart valves. As with other anticoagulants, careful assessment is needed for those with prior bleeding, gastric ulcers, or concurrent use of other anticoagulants or antiplatelets.

Reversal and perioperative management

In cases of major bleeding, apixaban should be discontinued; specific reversal with andexanet alfa is available in appropriate settings. Activated charcoal may be used if ingestion occurred within a short window. Prothrombin complex concentrates may be considered when reversal agents are not available or appropriate. Perioperative planning should balance bleeding risk with thrombosis risk.