Best Time to Take Aspirin 150 mg
For a 40-year-old adult with cardiovascular disease taking aspirin 150 mg for secondary prevention, evening dosing (at bedtime around 8:00 PM) provides superior platelet inhibition during the critical early morning hours when cardiovascular events are most likely to occur.
Dosing Timing Recommendation
Evening intake (bedtime) is preferable to morning intake based on the following evidence:
Morning aspirin intake results in the lowest platelet inhibition during early morning hours (6:00-8:00 AM), when cardiovascular events peak, with serum thromboxane B2 levels approximately twice as high (5843 pg) compared to evening dosing (2877 pg) 1
Evening aspirin intake significantly reduces morning platelet reactivity by 22 aspirin reaction units compared to morning dosing in patients with established cardiovascular disease 2
Bedtime aspirin reduces reticulated platelet levels in the evening and maintains higher platelet inhibition throughout the critical early morning window 3
Dose Adjustment Consideration
Your current 150 mg dose should be reduced to 75-162 mg daily (most commonly 81 mg in the U.S.):
The American Diabetes Association and American College of Cardiology recommend 75-162 mg daily for secondary prevention in patients with established cardiovascular disease 4, 5
The ADAPTABLE trial demonstrated no difference in cardiovascular events or major bleeding between 81 mg and 325 mg daily doses, indicating higher doses provide no additional benefit 4, 6
Lower doses (75-81 mg) minimize gastrointestinal bleeding risk while maintaining full cardiovascular efficacy 5, 7
Practical Implementation
Take 81 mg aspirin at bedtime (around 8:00 PM) rather than in the morning:
This timing provides optimal platelet inhibition during the 6:00-10:00 AM period when myocardial infarction and stroke incidence peaks 1, 3, 2
Evening dosing does not affect blood pressure differently than morning dosing, so timing can be chosen purely for antiplatelet optimization 2
Important Caveats
Continue aspirin indefinitely for secondary prevention as the cardiovascular benefits far outweigh bleeding risks in patients with established cardiovascular disease 4, 5, 6
Monitor for bleeding risk factors including age >70 years, history of gastrointestinal ulcers, anemia, chronic kidney disease, or concurrent use of NSAIDs or anticoagulants 5, 7, 6
If aspirin allergy is documented, substitute with clopidogrel 75 mg daily 4, 6