Aspirin Administered at Bedtime, But Not on Awakening, Has an Effect on Ambulatory Blood Pressure in Hypertensive Patients

Objectives The purpose of this research was to investigate in untreated hypertensive patients the effects on ambulatory blood pressure (BP) of aspirin (ASA) administered at different times of the day. Background Previous studies have shown that ASA produces an administration time-dependent inhibition of angiotensin II. Low-dose ASA has also been shown to reduce BP when administered before bedtime, as opposed to upon awakening, in normotensive and hypertensive volunteers, and in pregnant women at high risk for preeclampsia. Methods We studied 328 untreated patients with grade 1 hypertension, 44.0 +/- 12.6 years of age, randomly divided into three groups: nonpharmacological hygienic-dietary recommendations, the same recommendations and ASA (100 mg/day) on awakening, or the same recommendations and ASA before bedtime. Blood pressure was measured every 20 min during the day and every 30 min at night for 48 consecutive h before and after 3 months of intervention. Results After three months of nonpharmacological intervention, there was a small and nonsignificant reduction of BP (<0.2 mm Hg; p = 0.648). Blood pressure was slightly elevated after aspirin on awakening (2.6/1.6 mm Hg in the 24-h mean of systolic/diastolic BP; p = 0.002). A significant BP reduction, however, was observed in the patients who received aspirin before bedtime (6.8/4.6 mm Hg in systolic/diastolic BP; p < 0.001). Conclusions This prospective trial documents a significant administration time-dependent effect of low-dose ASA on BP in untreated hypertensive patients. The timed administration of low-dose ASA could provide a valuable approach, beyond the secondary prevention of cardiovascular disease, in the added BP control of patients with mild essential hypertension.