[Study of the placebo effect by the pressure profile method].

The effect of one tablet of placebo daily for 8 days on blood pressure was studied in 90 hypertensive patients, using the blood pressure profile method, with a 12-hour recording period (from 8 a.m. to 8 p.m) and readings every 15 minutes (Dinamam 845). Statistical analysis of the results showed no significant difference in diastolic, systolic and mean blood pressure in 50% of the cases. A significant decrease of about 10% in blood pressure without change in variability was observed in more than 20% (complete placebo effect) and in about 30% (total placebo effect) of the cases. A significant increase of about 8% on blood pressure was recorded in less than 20% of the cases. Almost 25% of the patients had a significant decrease in heart rate. There was no correlation between heart rate and blood pressure under placebo. These criteria, which are both qualitative and quantitative, can be taken as reference when the blood pressure profile method is used to evaluate the effectiveness of antihypertensive drugs.