A design for testing interventions to improve adherence within a hypertension clinical trial

The Potassium Adherence Clinical Trial (PACT) incorporates one randomized c linical trial within another. A randomized trial of interventions to increa se adherence to medication is nested within a second randomized clinical tr ial testing hypotensive effect of supplemental oral potassium. The trial ai ms principally to compare the effects of three intervention strategies: two sessions of individual patient counseling, two telephone contacts, or stan dard care. The trial aims secondarily to evaluate the effect of 60 mEq supp lemental oral potassium daily on sitting systolic and diastolic blood press ure in hypertensive patients on established drug therapy. Therefore, it org anizes the patients given potassium into three study groups for adherence i nterventions, and the patients assigned to placebo into a further three. We evaluate adherence primarily by means of the Medication Event Monitoring System (MEMS), an electronic system that records the date and time that th e container of study medication is opened. Additional measurements, such as assessments of change in levels of urinary potassium, pill counts, appoint ment records, self-reporting by patients, and estimates by physician of adh erence, are used and correlated with MEMS data. At a single center, the trial enrolled 107 participants between the ages of 26 and 80. This paper describes the background to this trial within a tria l, details its design, documents the baseline characteristics of participan ts enrolled, and describes issues experienced during implementation of the trial. Control Clin Trials 2000;21:62-72 (C) Elsevier Science Inc. 2000.