In search of strategies to improve compliance, we assessed medication-taking behavior among 19 ambulatory hypertensives, using both pill counts and electronic monitoring. The regimen consisted of one pill each day for less-than-or-equal-to 63 weeks with return visits at 1 to 4 week intervals. The study population was 79% male, 68% white, and 16% black with mean (+/- SEM) age 58.4 +/- 2.5 years. Only 51% of the intervisit intervals displayed greater-than-or-equal-to 80% of vial openings within the desirable range (24 +/- 6 h). Pill counts detected only 2% of suboptimal interdosing intervals identified by electronic monitoring. Early changes in compliance correlated well with later changes (r = 0.83, P = .002). A few of the subjects exhibited a large deviation from the prescription, uncorrectable with drugs having a long duration of action. We conclude that (a) pill counts tend to overestimate patients' compliance rates, (b) changes in medication-taking behavior early in therapy may predict subsequent compliance rates; and (c) prolonging drug action may compensate for some imperfect medication-taking behavior.
