Effect of antihypertensive therapy on the circadian blood pressure pattern.

This study employed 24-hour automated ambulatory blood pressure monitoring to evaluate whole-day patterns of blood pressure in age-matched groups of normotensive volunteers, untreated hypertensive patients, and hypertensive patients treated with prazosin. As would be expected, overall systolic and diastolic blood pressures were found to be lowest in the normotensive subjects and highest in the untreated hypertensive patients. The systolic and diastolic blood pressure values for patients receiving prazosin twice daily were significantly lower than in the untreated patients; they were slightly, but not significantly, higher than the values recorded for the normotensive volunteers. The data from 24-hour monitoring revealed no between-group differences in the actual circadian rhythm of the blood pressure. This finding established that the blood pressure pattern for hypertensive patients treated with prazosin was parallel to that for normal individuals. Thus, prazosin administered twice daily reduces blood pressure throughout a full 24-hour period in a fashion that maintains the normal circadian pattern of the blood pressure.