What are the initial doses of Aspirin (ASA) and Clopidogrel (Plavix) for acute ischemic CVA?

Initial Dosing of Dual Antiplatelet Therapy for Acute Ischemic Stroke

For acute ischemic stroke, the recommended initial dosing is aspirin 160-325 mg loading dose followed by 75-100 mg daily maintenance, plus clopidogrel 300-600 mg loading dose followed by 75 mg daily maintenance. 1

Loading Dose Recommendations

Aspirin Loading Dose

• Initial dose: 160-325 mg 2, 1
• Administration: Should be given within 48 hours of symptom onset 1
• Route: Oral preferred; can be given rectally (325 mg) or via enteral tube (80 mg) in patients with swallowing difficulties 1

Clopidogrel Loading Dose

• Initial dose: 300-600 mg 2, 3
• Higher loading dose (600 mg) provides more rapid and complete platelet inhibition 2
• With 300 mg loading dose, antiplatelet effects appear within 90 minutes and reach full effect within 6 hours 2

Maintenance Dose Recommendations

Aspirin Maintenance Dose

• Daily dose: 75-100 mg 2, 1
• Lower maintenance doses (81 mg) are preferred to minimize bleeding risk while maintaining efficacy 2

Clopidogrel Maintenance Dose

• Daily dose: 75 mg 2, 1, 3
• Should be continued for up to 90 days in high-risk patients 3, 4

Duration of Therapy

• For minor stroke or high-risk TIA: Dual antiplatelet therapy for 21-90 days 3, 4
• Recent evidence supports DAPT initiated within 72 hours (not just 24 hours) after stroke onset 4
• After the initial dual therapy period, transition to single antiplatelet therapy (typically clopidogrel 75 mg daily or aspirin 75-100 mg daily) 1

Clinical Evidence Supporting These Recommendations

• The POINT trial demonstrated that clopidogrel (600 mg loading, 75 mg daily) plus aspirin reduced recurrent stroke risk compared to aspirin alone when initiated within 24 hours (5.0% vs 6.5% at 90 days) 3
• The INSPIRES trial showed benefit of DAPT even when initiated within 72 hours after stroke onset (7.3% vs 9.2% stroke recurrence) 4
• The antiplatelet effects of clopidogrel with a 300 mg loading dose appear within 90 minutes, and after 6 hours, the effects are equivalent to those achieved after 10 days of therapy 2

Important Considerations and Pitfalls

• Bleeding risk: DAPT increases bleeding risk (0.9% vs 0.4% for aspirin alone) 3, so carefully assess bleeding risk before initiating
• Timing matters: Earlier initiation (within 24 hours) provides greater benefit in preventing recurrent events 3
• Loading dose importance: Without a loading dose, clopidogrel takes approximately 5 days to achieve maximal platelet inhibition 2
• Aspirin dose with clopidogrel: When used in combination with clopidogrel, lower aspirin doses (81 mg) provide similar antiplatelet effects with potentially lower bleeding risk compared to higher doses 5

Special Populations

• Patients with dysphagia: Consider aspirin rectally or via enteral tube; clopidogrel can be administered via enteral tube 1
• Patients with prior stroke or TIA history: Use caution with prasugrel (not recommended for this population) 2
• Elderly patients (>75 years): Consider lower loading doses due to increased bleeding risk

By following these dosing recommendations for dual antiplatelet therapy in acute ischemic stroke, you can optimize the reduction in recurrent stroke risk while minimizing bleeding complications.