What is the recommended dosage of aspirin (acetylsalicylic acid) for adults?

Recommended Dosage of Aspirin for Adults

The recommended dosage of aspirin for adults is 75-162 mg daily for cardiovascular prevention, with 81 mg being the most commonly prescribed dose in the United States as it provides effective cardiovascular benefits while minimizing bleeding risk. 1

Dosage Guidelines by Clinical Scenario

Primary Prevention

• For adults aged 50-59 years with ≥10% 10-year cardiovascular risk and low bleeding risk, 75-162 mg/day is recommended 1
• For adults aged 60-69 years, aspirin may be considered at 75-162 mg/day, but with smaller net benefit due to increased bleeding risk 1
• Not recommended for adults <50 years with low cardiovascular risk due to unfavorable benefit-risk ratio 1
• Not generally recommended for adults >70 years as bleeding risks typically outweigh benefits 1

Secondary Prevention

• For patients with established atherosclerotic cardiovascular disease (ASCVD), 75-162 mg/day is strongly recommended 1
• For acute coronary syndrome, a loading dose of 162-325 mg followed by 75-100 mg daily maintenance dose 2
• For patients with documented aspirin allergy, clopidogrel 75 mg/day should be used 1

Dosing Considerations

Optimal Dose Selection

• The lowest effective dose (75-100 mg daily) should be used to minimize gastrointestinal bleeding risk 3
• 81 mg daily is the most common low-dose tablet in the US and is generally sufficient for cardiovascular protection 1
• Clinical trials have used doses ranging from 50-650 mg daily, but most evidence supports 75-162 mg daily 1, 4
• The ADAPTABLE trial showed no significant differences in cardiovascular events or major bleeding between 81 mg and 325 mg daily doses in patients with established cardiovascular disease 1

Special Populations

• In diabetic patients, 75-162 mg/day may be considered for primary prevention in those with high cardiovascular risk and low bleeding risk 1
• Dual antiplatelet therapy (aspirin plus P2Y12 inhibitor) is recommended for 1 year after acute coronary syndrome 1, 2
• Aspirin is contraindicated in patients <21 years due to risk of Reye syndrome 1

Safety Considerations

Bleeding Risk

• Major bleeding risk increases with aspirin use, from 3.2% to 4.1% in primary prevention studies 1
• Gastrointestinal bleeding risk may be as high as 5 per 1,000 person-years in real-world settings 1, 2
• Risk factors for bleeding include older age, history of GI bleeding, concurrent NSAID or anticoagulant use, and uncontrolled hypertension 2

Risk-Benefit Assessment

• For patients with >1% annual ASCVD risk, the number of cardiovascular events prevented is similar to or greater than bleeding events induced 1, 2
• Benefit-risk ratio is most favorable in secondary prevention 1
• Shared decision-making is important, especially in primary prevention scenarios 1

Administration

• Aspirin should be taken with a full glass of water 5
• Non-enteric coated aspirin should be chewed when possible for rapid onset of antiplatelet action in acute settings 2
• Daily administration is preferred over alternate-day dosing for cardiovascular prevention 6

Remember that while FDA-approved analgesic dosing may be higher (up to 4-8 tablets every 4 hours), cardiovascular prevention requires much lower doses to optimize the benefit-risk ratio 5, 3.