Volume 50 | Number 2 | April 2015

Abstract List

Andrew J. Karter Ph.D., Melissa M. Parker M.S., O. Kenrik Duru M.D., M.S.H.S., Dean Schillinger M.D., Nancy E. Adler Ph.D., Howard H. Moffet M.P.H., Alyce S. Adams Ph.D., James Chan Pharm.D., Ph.D., Willam H. Herman M.D., M.P.H., Julie A. Schmittdiel Ph.D.


To assess the impact of a pharmacy benefit change on mail order pharmacy () uptake.

Data Sources/Study Setting

Race‐stratified, random sample of diabetes patients in an integrated health care delivery system.

Study Design

In this natural experiment, we studied the impact of a pharmacy benefit change that conditionally discounted medications if patients used and prepaid two copayments. We compared uptake among those exposed to the benefit change ( = 2,442) and the reference group with no benefit change ( = 8,148), and estimated differential uptake across social strata using a difference‐in‐differences framework.

Data Collection/Extraction Methods

Ascertained uptake (initiation among previous nonusers).

Principal Findings

Thirty percent of patients started using after receiving the benefit change versus 9 percent uptake among the reference group ( < .0001). After adjustment, there was a 26 percentage point greater uptake (benefit change effect). This benefit change effect was significantly smaller among patients with inadequate health literacy (15 percent less), limited English proficiency (14 percent less), and among Latinos and Asians (24 and 16 percent less compared to Caucasians).


Conditionally discounting medications delivered by effectively stimulated uptake overall, but it unintentionally widened previously existing social gaps in use because it stimulated less uptake in vulnerable populations.