Apixaban selectively inhibits factor Xa, a key enzyme in the coagulation cascade. The mechanism of action involves:

1. Inhibition of Factor Xa:
   • Factor Xa plays a critical role in the conversion of prothrombin to thrombin, a key step in blood clot formation.
   • By inhibiting factor Xa, apixaban reduces thrombin generation, thereby preventing the formation of blood clots.
2. Anticoagulant Effect:
   • Apixaban’s action is specific to factor Xa, making it a targeted anticoagulant with a lower risk of affecting other clotting factors.
   • It does not require antithrombin III (unlike heparin) for its activity.
3. Predictable Pharmacokinetics:
   • Apixaban has a rapid onset of action, reaching peak plasma concentrations within 3–4 hours.
   • It has a half-life of approximately 12 hours, allowing for twice-daily dosing.

Apixaban is approved for the following conditions:

1. Prevention of Stroke and Systemic Embolism in Atrial Fibrillation:
   • Used in patients with non-valvular atrial fibrillation (NVAF) to reduce the risk of stroke and systemic embolism.
2. Treatment and Prevention of Deep Vein Thrombosis (DVT) and Pulmonary Embolism (PE):
   • Used for the treatment of acute DVT and PE.
   • Also used for the prevention of recurrent DVT and PE.
3. Postoperative Thromboprophylaxis:
   • Used to prevent venous thromboembolism (VTE) in patients undergoing hip or knee replacement surgery.

the dosage of apixaban varies depending on the indication and patient-specific factors. Below are general guidelines:

1. Atrial Fibrillation (Stroke Prevention):
   • Standard Dose: 5 mg taken orally twice daily.
   • Reduced Dose: 2.5 mg twice daily for patients with at least two of the following:
     • Age ≥ 80 years
     • Body weight ≤ 60 kg
     • Serum creatinine ≥ 1.5 mg/dL
2. Treatment of DVT and PE:
   • Initial Dose: 10 mg taken orally twice daily for the first 7 days.
   • Maintenance Dose: 5 mg taken orally twice daily.
3. Prevention of Recurrent DVT and PE:
   • Standard Dose: 2.5 mg taken orally twice daily.
4. Postoperative Thromboprophylaxis:
   • Standard Dose: 2.5 mg taken orally twice daily, starting 12–24 hours after surgery.
   • Duration:
     • Hip replacement: 32–38 days.
     • Knee replacement: 10–14 days.
5. Administration:
   • Apixaban can be taken with or without food.
   • Do not crush or chew the tablets.

Apixaban is generally well-tolerated, but some side effects may occur. These include:

1. Common Side Effects:
   • Bleeding (e.g., nosebleeds, gum bleeding, bruising)
   • Nausea
   • Anemia
2. Less Common Side Effects:
   • Headache
   • Rash
   • Elevated liver enzymes
3. Rare but Serious Side Effects:
   • Major Bleeding: Gastrointestinal bleeding, intracranial hemorrhage.
   • Hypersensitivity Reactions: Rare cases of anaphylaxis or angioedema.
   • Spinal/Epidural Hematoma: Especially in patients undergoing spinal procedures.

1. Contraindications:
   • Hypersensitivity to apixaban or any component of the formulation.
   • Active clinically significant bleeding.
   • Severe hepatic impairment (Child-Pugh class C).
2. Warnings:
   • Bleeding Risk: Apixaban increases the risk of bleeding. Use with caution in patients with a history of bleeding disorders or conditions that predispose to bleeding.
   • Renal Impairment: Use with caution in patients with severe renal impairment (CrCl < 15 mL/min). Dose adjustment may be required.
   • Pregnancy and Lactation: Apixaban is not recommended during pregnancy or breastfeeding unless the benefits outweigh the risks.
3. Monitoring:
   • Regular monitoring of renal function (serum creatinine).
   • Watch for signs of bleeding (e.g., unusual bruising, blood in stool or urine).

Apixaban interacts with several medications, including:

1. Strong CYP3A4 and P-gp Inhibitors (e.g., ketoconazole, ritonavir): Increase apixaban levels, increasing the risk of bleeding. Avoid concurrent use or reduce the dose of apixaban.
2. Strong CYP3A4 and P-gp Inducers (e.g., rifampin, carbamazepine): Decrease apixaban levels, reducing its efficacy. Avoid concurrent use.
3. Other Anticoagulants (e.g., warfarin, heparin): Increased risk of bleeding.
4. NSAIDs (e.g., ibuprofen): Increased risk of gastrointestinal bleeding.

Antiplatelet Agents (e.g., aspirin, clopidogrel): Increased risk of bleeding

Apixaban is available under its generic name as well as brand names. Some common formulations include:

• Generic Name: Apixaban
• Brand Name: Eliquis (commonly used worldwide).