Objective: To search for major gaps in medication-taking behavior predisposing patients to cardiovascular morbidity and mortality.
Design: Convenience sample; cohort prospectively followed for < or = 5 months.
Setting: General internal medicine and cardiology clinics in a university medical center.
Patients: From among 893 patients, the authors identified 132 eligible individuals and entered 33 subjects (25%) with chronic cardiovascular conditions, 1-3 chronic oral medications for these conditions, overall regimen of < or = 6 drugs, regular visits at 1-3-month intervals, literacy in English, willingness to use electronic monitors, and physician permission to participate.
Outcome measures: Medication compliance rates and patterns by patient self-report, physician estimates, pill count, and electronic monitoring of pill vial opening.
Results: Despite moderately complex regimens (5.4 +/- 0.5 pills daily; range 1-11), most subjects took most medications according to the prescription: median intervals between pill vial openings were 1.00, 0.50, and 0.43 days for once, twice, and three times daily dosing, respectively. Medication-taking gaps of > or = 2 times the prescribed interdosing interval occurred for 48% of the patients. Patients' dosing patterns often produced "uncovered" intervals (mean duration 3.7 days, range 0-25) with doubtful pharmacologic effectiveness. These lapses were underestimated by patients and poorly perceived by their treating physicians, despite familiarity with their care. Baseline sociodemographic, psychosocial, medical system, or clinical characteristics did not predict the patterns or degrees of medication noncompliance.
Conclusions: Major treatment gaps occur frequently, even in carefully selected ambulatory populations, and generally escape detection. The compliance patterns and gaps may contribute to reported excesses of cardiovascular morbidity and mortality.