Use of prescription-refill records to assess patient compliance.

Prescription-refill records were used to assess patient compliance, to evaluate factors previously associated with compliance, and to determine the association between selected drugs and compliance. Records were selected from a computerized database containing prescription-coverage claims, based on the following criteria: (1) the prescriptions were refilled during 1987-1989 and within two times the days' supply after the dispensing date, (2) they involved any of 12 drugs selected for study, (3) they required one to four doses per day, and (4) at least 20 records with the same regimen were available. Compliance was defined as refill within 0.2 times the days' supply after the refill-due date, and it was assessed by calculating the compliance rate and the compliance index (which describes the relationship between the refill-due date and the actual refill date). Data from 19,118 prescription-refill records were analyzed. The compliance index improved slightly as the number of concurrent medications increased, worsened as the number of doses per day increased, and improved as the immediacy of the risk of noncompliance increased. Different medications and indications were associated with different degrees of compliance. Medication compliance generally improves as the number of daily doses decreases, may improve slightly as the number of concurrent medications increases, and varies with the particular drug and indication.