Aspirin Does Not Lower Blood Pressure
Aspirin does not lower blood pressure and should not be used as an antihypertensive agent. In fact, like other nonsteroidal anti-inflammatory drugs (NSAIDs), aspirin may slightly increase blood pressure or interfere with blood pressure control, though low-dose aspirin (75-100 mg daily) appears to have minimal clinically significant effects on blood pressure in treated hypertensive patients 1, 2.
Evidence Against Blood Pressure Lowering Effects
The highest quality evidence demonstrates that low-dose aspirin does not reduce blood pressure:
In the Primary Prevention Project (PPP) study of 142 hypertensive patients on stable antihypertensive therapy, 3 months of aspirin 100 mg daily produced no statistically significant changes in either clinic blood pressure or 24-hour ambulatory blood pressure monitoring compared to controls 2
The Hypertension Optimal Treatment (HOT) Study, which randomized 18,790 hypertensive patients to aspirin 75 mg daily versus placebo for 3.8 years, found that blood pressure values achieved were "superimposable" between aspirin and placebo groups, with clinically irrelevant differences 3
Cohort studies actually show an 18% increase in the risk of developing hypertension among aspirin users 1
Why the Confusion Exists
Some uncontrolled, unmasked trials have suggested that aspirin administered at bedtime might lower blood pressure, but these studies are potentially biased and conflict with the higher-quality controlled evidence 1. These methodologically flawed studies should not guide clinical practice.
What Aspirin Actually Does in Hypertensive Patients
Aspirin's role in hypertension is for cardiovascular event prevention, not blood pressure reduction:
In the HOT Study, aspirin 75 mg daily reduced major cardiovascular events by 15% and myocardial infarction by 36% in well-controlled hypertensive patients, independent of any blood pressure effects 4, 5
Low-dose aspirin (75-162 mg daily) is recommended for hypertensive patients aged ≥50 years with controlled blood pressure (<150/90 mmHg) who have target organ damage, diabetes, or 10-year cardiovascular risk >15% 4, 6
Clinical Implications
For blood pressure management:
- Use proven antihypertensive medications (ACE inhibitors, calcium channel blockers, diuretics, beta-blockers, ARBs) 4
- Do not prescribe aspirin with the expectation of lowering blood pressure 1
For cardiovascular risk reduction in hypertensive patients:
- Consider low-dose aspirin (75-100 mg daily) once blood pressure is adequately controlled 6, 5
- The cardiovascular benefits of aspirin are independent of blood pressure effects 3
Important Safety Consideration
Low-dose aspirin does not significantly interfere with the blood pressure-lowering effects of antihypertensive drugs, including ACE inhibitors, making it safe to use concurrently for cardiovascular protection 2, 3. However, uncontrolled hypertension increases bleeding risk with aspirin and should be addressed before initiating aspirin therapy 4.