Aims of ambulatory blood pressure monitoring during phase II and III clinical trials.

Ambulatory blood pressure monitoring (ABPM) is now widely used for the assessment of antihypertensive agents. This procedure may be used in phase II studies in dose-ranging evaluations. Indeed, ABPM provides data more appropriate for determining the dose-response relationship than are those from conventional blood pressure measurement. For each dose, it is possible to investigate both the magnitude and the duration of the antihypertensive effect. For these phase II studies, more accurate findings may be obtained by excluding patients for whom the diagnosis of hypertension is based on clinic readings only. ABPM tends to be used increasingly in clinical trials. An important advantage of this technique is to determine whether the complete dose interval is covered by the drug and to prove such a sustained duration of action in the natural environment of the patient. Because clinical decisions concerning management of hypertension are always based on office blood pressure measurement, entry criteria for these studies cannot derive from ABPM data but subgroup analyses may take ABPM data into account. The better intrasubject reproducibility of ABPM has been proposed to reduce the number of subjects needed for a clinical trial. This advantage seems to be more significant for cross-over studies. ABPM could reveal more easily than does conventional blood pressure measurement minimal differences in efficacy and duration of action between two different drugs. ABPM might help to quantify objectively the trough: peak effect ratio of an antihypertensive drug. Indeed, it allows better recognition of the real peak effect but the real-life conditions may be disadvantageous in calculating the ratio.