Patterns of drug compliance with medications to be taken once and twice daily assessed by continuous electronic monitoring in primary care.

Adherence to drug treatment is difficult to assess in routine medical practice. Therefore, electronic compliance monitoring and a new computer software program, the PC-RDP (Reader, Display, Printer) system was used. It allows instant evaluation of a patient's dosing record, at the patient's return to the practice. Compliance was measured in 24 patients on antihypertensive treatment, either continuous (n = 8) or newly prescribed treatment (n = 16) in primary care, for a total period of 5144 patient days. Fifteen patients received compliance feedback by their physician, 9 did not receive feedback. The drugs prescribed were triamterene plus hydrochlorothiazide, as a single dose, once daily (QD), and nifedipine twice daily (BID). The mean percentages of prescribed doses taken were 89% (QD) and 88% (BID). Partial compliance was 10 times more often (1243 days) than overcompliance (114 days), and days without dosing were observed twice as frequently with the QD than the BID regimen. Omissions of doses occurred more often on weekends than any other day of the week. With the BID regimen, evening doses were omitted twice as often as morning doses. When treatment was initiated, compliance was consistently high until the end of the study period, whereas in patients on continuous treatment, it decreased over time. Both compliance feedback (n = 11/16) and the beginning of treatment may be important factors to explain the difference in compliance behavior. An implementation of compliance monitoring into practical patient care seems to be feasible and promising.