Time to Filling of New Prescriptions for Chronic Disease Medications Among a Cohort of Elderly Patients in the USA.

Background: Data on primary nonadherence remains sparse, due to a lack of data resources that combine information on medication prescribing and dispensing. In addition, previous work on primary nonadherence has used follow-up periods ranging from 30 days up to 18 months, making results difficult to compare.

Objective: To evaluate the prevalence and predictors of primary nonadherence by measuring time until filling in a cohort of elderly patients.

Design: Retrospective cohort study of new prescription episodes.

Patients: Data comes from a linked database of electronic health records and claims for patients aged ≥ 65 years enrolled in Medicare Parts A, B, and D during 2007-2014. We identified patients receiving a new prescription for a chronic disease medication with continuous Medicare enrollment for 180 days prior to the index prescription order and no fills or orders for the medication during this period.

Main Measures: Time until filling of the index prescription for up to 1 year.

Key Results: In 32,586 new medication orders, the majority (75%; 95% confidence interval [CI] 74-75%) of new prescriptions were filled within 7 days, 81% (81-82%) were filled within 30 days, and 91% (91-92%) were filled within 1 year. The rate and timing of dispensing were similar across therapeutic areas. Timing of initial filling within 7 days or within 30 days could be predicted with moderate accuracy (C-statistics = 0.70-0.74). Patients with > 5 current medications on hand at the time of the index prescription and average out-of-pocket medication costs < $5 filled 89% of prescriptions within 7 days. Patients with no current medications and out-of-pocket costs > $50 filled only 25% of prescriptions within 7 days.

Conclusions: Nearly 20% of patients do not fill a new chronic disease prescription within 30 days. Patients with fewer recent fills and higher out-of-pocket costs are at higher risk of primary nonadherence.