Ambulatory blood pressure in relation to drug treatment and clinical trials.

Spontaneous differences in blood pressure from one clinic visit to another inevitably lead to the use of unnecessarily high doses of drugs in the treatment of hypertension and to unnecessarily high recommended doses of new antihypertensive drugs. This can be avoided by the use of ambulatory blood pressure monitoring. The improved reproducibility achieved by ambulatory monitoring substantially reduces the number of subjects required to detect small differences in pressure between one treatment and another. Furthermore, 24-h monitoring eliminates time-related fluctuations and makes it possible to use crossover trials to compare the antihypertensive effects of different drugs. Differences of 5 mmHg in diastolic pressure between two treatments can thus be detected in a trial on less than 20 subjects.