Ambulatory blood pressure monitoring in the design of studies on antihypertensive drug efficacy.

Ambulatory blood pressure monitoring (ABPM) provides advantages for studies of the efficacy of antihypertensive drugs in addition to demonstrating antihypertensive effects in daily life conditions. For example, ABPM is devoid of the "white coat" effect and can thus more precisely estimate the relative proportion of responders and nonresponders to treatment. It also may reduce the study size because of the greater reproducibility of 24 h average blood pressure (BP) (as compared to clinic BP) and the lack of a substantial placebo effect, which eliminates the need for a placebo group. Some disadvantages exist, including the inability of automatic ABPM to consistently provide accurate BP readings and to estimate BP variability. Finally, hourly average BPs are less reproducible than their average 24 h counterpart, which may make it more difficult to statistically demonstrate an antihypertensive effect throughout the 24 h. Some of these disadvantages, however, may be reduced in the near future by new ABPM devices.