Study of the placebo effect in using the non-invasive ambulatory measurement of blood pressure

The aim of this study is to evaluate the antihypertensive effect of placebo assessed by 24 hr non invasive blood pressure monitoring. 20 patients (16 males, 4 females, 55 +/- 10 years old) with primary hypertension (WHO stage I or II) were included with a diastolic blood pressure greater than or equal to 100 mmHg (mean blood pressure from three clinical readings). Casual blood pressure and blood pressure monitoring (Spacelabs - 4 measurements per hour during a 24 hr period) were established before and at the end of the placebo run in period (one placebo tablet given once daily at 8 h-8 h 30 a.m. for 15 days). Overall sample data: There was no antihypertensive effect of the placebo with casual BP (167 +/- 16-109 +/- 6 mmHg before and 167 +/- 16-109 +/- 7 mmHg after placebo) and with 24 hr B.P. monitoring (142 +/- 14-96 +/- 8 mmHg before and 141 +/- 14-96 +/- 8 mmHg after placebo). The circadian curves were similar. Individual patient data: A clinical placebo effect (B.P. decrease of at least 10 mmHg) was found in 5 patients for the systolic B.P. and in 2 for diastolic B.P. A significant ambulatory placebo effect (p less than 0.05) was found in 5 patients for the 24 hr systolic B.P. and in 4 patients for the 24 hr diastolic B.P. However, patients with clinical placebo effect were not the same as those with ambulatory placebo effect. There was no correlation between the clinical and the ambulatory response to placebo treatment.(ABSTRACT TRUNCATED AT 250 WORDS)