Objective  To evaluate medication adherence and treatment outcomes in elderly outpatients using daily-dose blister packaging (Pill Calendar) compared with medications packaged in bottles of loose tablets.

Design  Randomized controlled trial.

Setting  Ambulatory care clinics at Ohio State University Medical Center, Columbus; University of Arizona Health Science Center, Tucson; and Riverside Methodist Hospital Family Medicine Clinic, Columbus, Ohio, from July 1, 2002, to December 31, 2004.

Patients  85 individuals 65 years of age or older being treated with lisinopril for hypertension.

Intervention  Patients were randomly assigned to receive lisinopril in either daily-dose blister packaging (Pill Calendar) or traditional bottles of loose tablets.

Main outcome measures  Adherence was assessed by prescription refill regularity and medication possession ratio (MPR). Treatment outcome and use of medical services were assessed by medical record review of blood pressure and morbidity associated with poorly controlled hypertension.

Results  Patients receiving lisinopril in the daily-dose blister packaging (Pill Calendar) refilled their prescriptions on time more often (P = 0.01), had higher MPRs (P = 0.04), and had lower diastolic blood pressure (P = 0.01) than patients who had their medications packaged in traditional bottles of loose tablets.

Conclusion  Providing medications in a package that identifies the day each dose is intended to be taken and provides information on proper self-administration can improve treatment regimen adherence and treatment outcomes in elderly patients.