Factors Associated with First-Fill Adherence Rates for Diabetic Medications: A Cohort Study

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Abstract
Little is known about first-fill adherence rates for diabetic medications and factors associated with non-fill. 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. Retrospective, cohort study linking electronic health records and pharmacy claims. 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. The primary outcome of interest was naïve prescription filled by the patient within 30 days of the prescription order date. 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. 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.