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Study Objective. To assess the accuracy of patient-kept diaries relative to electronic monitoring of compliance with isosorbide dinitrate prescribed 3 times/day for ischemic heart disease.

Design. Unblinded, prospective, three-phase study.

Methods. Patients with coronary artery disease prescribed isosorbide dinitrate 3 times/day were asked to record the time of administration of each dose in a pocket diary while being monitored for compliance with a computerized Medication-Event Monitoring System (MEMS-4) vial that electronically recorded the date and time the vial was opened.

Results. Sixty-eight stable outpatients with documented coronary artery disease who were prescribed isosorbide dinitrate 3 times/day were evaluated. Based on a prospectively chosen definition including a nitrate-free period, the mean (± SD) overall compliance rates were 71% (± 30) versus 55% (± 32) for the patient-kept diaries and the MEMS vials respectively (p=0.001). The concordance between patient-kept diaries and MEMS data indicate that 67% of patients overestimate their compliance when using a self-recording tool. An average of 30% of diary entries were in error compared with the MEMS vial recordings.

Conclusions. Patient-kept diaries statistically overestimate actual compliance relative to that determined by MEMS devices. Given the prevalence of the use of diaries as the predominant tool on which researchers depend to document compliance with study drugs, our findings suggest that this practice should be reevaluated specifically when the time of the dose and documentation of administration are critical to qualifying the outcome of drug therapy. Such is the case with isosorbide dinitrate use in patients with ischemic heart disease. Furthermore, the overall poor compliance documented in this study suggests that the utility of isosorbide dinitrate prescribed 3 times/day be reevaluated as a clinically effective antianginal drug.