Factors associated with first-fill adherence rates for diabetic medications: a cohort study.

Abstract

BACKGROUND: Little is known about first-fill adherence rates for diabetic medications and factors associated with non-fill. OBJECTIVE: To assess the proportion of patients who fill their initial prescription for a diabetes medication, understand characteristics associated with prescription first-fill rates, and examine the effect of first-fill rates on subsequent A1c levels. DESIGN: Retrospective, cohort study linking electronic health records and pharmacy claims. PARTICIPANTS: One thousand one hundred thirty-two patients over the age of 18 who sought care from the Geisinger Clinic, had Geisinger Health Plan pharmacy benefits, and were prescribed a diabetes medication for the first time between 2002 and 2006. MEASUREMENTS: The primary outcome of interest was naïve prescription filled by the patient within 30 days of the prescription order date. RESULTS: The overall first-fill adherence rate for antidiabetic drugs was 85%. Copays < $10 (OR 2.22, 95% CI 1.57-3.14) and baseline A1c > 9% (OR 2.63, 95% CI 1.35, 5.09) were associated with improved first-fill rates while sex, age, and co-morbidity score had no association. A1c levels decreased among both filling and non-filling patients though significantly greater reductions were observed among filling patients. Biguanides and sulfonylureas had higher first-fill rates than second-line oral agents or insulin. CONCLUSIONS: First-fill rates for diabetes medication have room for improvement. Several factors that predict non-filling are readily identifiable and should be considered as possible targets for interventions.