Evaluation of the antihypertensive effect of nocturnal administration of acetylsalicylic acid: a cross-over randomized clinical trial

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Several studies have shown that evening intake of aspirin has antihypertensive effect in healthy adults, which has not been proven in patients with cardiovascular disease, who mostly take aspirin in the morning. We have evaluated the antihypertensive effect of bedtime administration of aspirin in patients with cardiovascular disease already treated for hypertension.


This is a multicenter randomized triple-blind placebo-controlled crossover trial, with hypertensive patients treated with aspirin for secondary prevention. There was a baseline-randomized assignment to 2-month periods of bedtime aspirin (100 mg) first and morning-time aspirin later, or inversely, both periods separated by an open label 2–4 weeks period of morning-time aspirin. At the start and end of each treatment period, a 24-h ambulatory blood pressure monitoring was performed. The main outcome measure was mean 24-h blood pressure. The analyses were performed according to the intention-to-treat principle.


Overall, 225 patients were randomized. No significant differences were observed in ambulatory blood pressure by time of intake of usual low doses of aspirin. The mean SBP/DBP was 123.2/69.9 (95% CI 121.58–124.9/68.86–76.86) with bedtime administration and 122.4/68.8 (95% CI 120.76–124.01/67.85–69.83) with daytime administration (P = 0.3 and P = 0.23 for SBP and DBP, respectively).


Administering aspirin at bedtime rather than in the morning does not modify the 24-h ambulatory blood pressure in hypertensive patients in secondary cardiovascular prevention.


The trial was registered with ClinicalTrials.gov (number NCT01741922).

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