Judging the effectiveness of antihypertensive therapy in an individual patient.

The physician's decision as to whether a hypertensive drug has produced satisfactory blood pressure lowering is more difficult than it is usually perceived to be. Variability of blood pressure, regression to the mean and habituation to the taking of blood pressure all conspire to blur the significance of the observed drop. We present algorithms outlining the number of visits before and after the initiation of therapy and the mmHg drop required for determination with acceptable certainty that any response to the hypotensive drug has occurred. Our conclusion is that the variability of blood pressure limits the clinician's ability to confidently conclude that antihypertensive therapy is effective unless the change in blood pressure exceeds a relatively high threshold and/or the number of visits both before and after the initiation of antihypertensive therapy is large. Because regression to the mean will be minimized, fewer visits and/or a lesser blood pressure fall in the treated patient changing or adding medications will be necessary to determine that a real decline has occurred.