What is the recommended dose of apixaban (Direct Oral Anticoagulant) for Deep Vein Thrombosis (DVT) prophylaxis in a 75-year-old female with no known renal impairment?

Apixaban Dosing for DVT Prophylaxis in a 75-Year-Old Female

For DVT prophylaxis after major orthopedic surgery (hip or knee replacement), the recommended dose is apixaban 2.5 mg orally twice daily, starting 12-24 hours post-operatively, for 12 days after knee replacement or 35 days after hip replacement. 1, 2

Context-Specific Dosing Recommendations

Post-Orthopedic Surgery Prophylaxis

• Initiate apixaban 2.5 mg orally twice daily beginning 12-24 hours after surgery 1, 2
• Duration varies by procedure:
  • Hip replacement: 35 days of treatment 1, 2
  • Knee replacement: 12 days of treatment 1, 2
• This dosing applies regardless of age, including patients ≥75 years 1

Medical Prophylaxis (Non-Surgical)

• Apixaban 2.5 mg twice daily for 30 days was NOT superior to enoxaparin for VTE prophylaxis in acutely ill medical patients and was associated with increased major bleeding 1
• Based on this evidence, apixaban is not recommended for routine medical prophylaxis in hospitalized patients 1

Age-Related Considerations for This 75-Year-Old Patient

No Dose Adjustment Required for Prophylaxis

• The 2.5 mg twice daily prophylactic dose remains unchanged at age 75 1
• Age-based dose reduction criteria (2.5 mg twice daily) apply only to atrial fibrillation treatment, not prophylaxis, and require age ≥80 years PLUS at least one additional criterion (weight ≤60 kg OR creatinine ≥1.5 mg/dL) 3, 2

Increased Bleeding Risk Awareness

• Patients ≥75 years have increased risk of gastrointestinal and intracranial bleeding with DOACs compared to younger patients 1
• Dabigatran and rivaroxaban specifically show increased GI bleeding in patients ≥75 years, though apixaban data shows favorable bleeding profiles 1
• Monitor closely for bleeding signs and symptoms and educate the patient accordingly 1

Renal Function Monitoring

Essential Pre-Treatment Assessment

• Check creatinine clearance (CrCl) using Cockcroft-Gault formula before initiating therapy 1
• Apixaban has 27% renal elimination, making it more favorable than other DOACs in renal impairment 1, 3

Dosing Adjustments Based on Renal Function

• CrCl >50 mL/min: Standard prophylactic dose of 2.5 mg twice daily 1
• CrCl 30-50 mL/min: Standard prophylactic dose of 2.5 mg twice daily (no adjustment needed for prophylaxis) 1
• CrCl 15-30 mL/min: Use with caution; apixaban should be avoided in severe renal impairment 1, 2
• CrCl <15 mL/min: Contraindicated 1, 2

Critical Safety Considerations

Drug Interactions to Avoid

• Avoid concurrent use with combined P-glycoprotein AND strong CYP3A4 inhibitors (e.g., ketoconazole, ritonavir) 1
• If such combinations are necessary, consider alternative anticoagulation 3
• Avoid combination with other anticoagulants, antiplatelets (except when specifically indicated), NSAIDs, SNRIs, or SSRIs due to increased bleeding risk 1

Contraindications

• Active bleeding 1
• Severe hepatic impairment (transaminases >2× upper limit of normal OR total bilirubin >1.5× upper limit of normal) 1, 3
• Intracranial vascular malformations 4

Neuraxial Anesthesia Precautions

• Do NOT perform spinal or epidural anesthesia if insufficient discontinuation time has elapsed 1
• Risk of spinal/epidural hematoma with potential permanent paralysis 2
• For high-risk procedures requiring neuraxial anesthesia, discontinue apixaban at least 48 hours prior 2

Common Pitfalls to Avoid

Incorrect Dose Selection

• Do NOT use the 5 mg twice daily dose for prophylaxis—this is the treatment dose for acute VTE after the initial 7-day loading period 1, 2
• Do NOT apply atrial fibrillation dose-reduction criteria (age ≥80, weight ≤60 kg, creatinine ≥1.5 mg/dL) to prophylaxis dosing 3, 2

Timing Errors

• Do NOT start apixaban immediately post-operatively—wait 12-24 hours to reduce bleeding risk 1, 2
• Do NOT double the dose if a dose is missed—take as soon as remembered on the same day and resume twice-daily schedule 2

Inadequate Monitoring

• Recheck renal function postoperatively if the surgical procedure or medical condition could affect kidney function 1
• No routine laboratory monitoring is required for apixaban efficacy, as it provides predictable anticoagulation at fixed doses 4

Alternative Scenarios

If This Were Treatment (Not Prophylaxis) of Acute DVT

• Initial loading dose: 10 mg orally twice daily for 7 days 1, 4, 2
• Maintenance dose: 5 mg orally twice daily for at least 3 months (provoked) or consider indefinite therapy (unprovoked) 1, 4
• Extended prevention: 2.5 mg orally twice daily after completing at least 6 months of full-dose therapy 4, 5, 2