Background and objectives: Previous studies on the potential influence of aspirin (AAS) on blood pressure have not taken in consideration the chronopharmacologic effects of non-steroidal antiinflammatory drugs. This pilot study investigated the effects of AAS on blood pressure in hypertensive patients under no antihypertensive treatment who received AAS at different day times according to their rest-activity cycle.
Patients and method: We studied 64 untreated patients with mild hypertension (24 men), 43.5 (12.0) (mean [SD]) years of age, randomly divided in 3 groups: group 1, non-pharmacological hygienic-dietetic recommendations; group 2, the same recommendations plus AAS (100 mg/day) on awakening, and group 3, the same recommendations plus AAS (100 mg/day) before bedtime. Blood pressure was measured every 20 min during the day and every 30 min at night for 48 consecutive hours before and after 3 months of intervention. The circadian pattern of blood pressure in each group was established by population multiple-component analysis. Circadian parameters obtained for each group of patients before and after the intervention were compared with a nonparametric paired test.
Results: After 3 months of non-pharmacological intervention, there was a small and non-significant reduction of blood pressure (< 1.5 mmHg; p = 0.28). There was no change in blood pressure when AAS was given on awakening (p = 0.21). A highly significant blood pressure reduction was, however, observed in patients who received AAS before bedtime (decrease of 7 and 5 mmHg in systolic and diastolic blood pressure, respectively; p = 0.006).
Conclusions: Our results indicate a statistically significant time-dependent administration effect of low-dose AAS on blood pressure in untreated patients with mild hypertension. This effect reinforces the need to quantify and control AAS effects in patients using this agent in combination with antihypertensive agents.