[Differences in the reduction of blood pressure according to drug administration at activity hours or rest hours]. / Diferencias en la reducción de la presión arterial en función de la toma de la medicación en horario diurno o nocturno.

BACKGROUND AND OBJECTIVE: In this study, 123 recordings of blood pressure (BP) obtained by ambulatory BP monitoring were analyzed. These recordings were measured in 2011 in patients from a Spanish tertiary university hospital. All participating patients were treated with 2, 3 or 4 anti-hypertensive drugs. The main aim of this study was to determine differences in BP control, if any, depending on the medication schedule. Thus, BP levels were studied at 3 periods of the day: activity hours, rest hours and 24h. PATIENTS AND METHOD: We compared subjects taking all anti-hypertensive agents during the day (n=70, group 1) with those taking at least one at night (n=53, group 2). RESULTS: Significant differences were found on diastolic BP, where group 2 patients had lower levels at activity, 24h periods and sleep-time. Even if it was not statistically significant, lower levels of systolic BP from group 2 were also observed at activity and 24h periods as well as lower levels of systolic, diastolic and mean BP at rest hours periods. There were also significant group differences in relation to the number of prescribed agents (with the mean being higher for group 2) and the type of agent (beta-blockers and calcium antagonists were more prevalent in group 2). Nevertheless, the multivariate regression analysis done taking into account these variables did not change the observed statistical significance. CONCLUSION: The administration of anti-hypertensive drugs at night could be associated with lower BP levels.