Factors Influencing Prescription Drug Synchronization: The Complex Role of Number of Medications.

Background: Despite the well-documented association of medication refill synchronization with medication adherence, little is known about how best to measure synchronization at pharmacy visits or about its relationship to number of medications.

Objective: To examine the relationship of a commonly cited synchronization measure with the number of prescription medications.

Methods: Using a cohort of women aged 66-90 years with stage 0-3 hormone receptor-positive breast cancer from the Surveillance, Epidemiology and End Result (SEER)-Medicare data, we identified women with pharmacy claims for at least 1 endocrine therapy prescription and at least 1 other medication fill. Twelve-month medication refill synchronization was calculated as the quotient of the number of pharmacy visits and the number of filled medications subtracted from 1. Multiple linear regression (including polynomials) was then used to assess the relationship between refill synchronization, number of medications, and other potentially influential factors.

Results: Over 47% of cohort subjects took more than 10 unique medications. Subjects made an average (SD) of 29.9 (18.0) pharmacy visits, resulting in a mean (SD) synchronization of 0.28 (0.18, range = 0.0-0.92). The number of medications, including powers through to the fourth, was strongly associated with refill synchronization, with a rapid initial rise followed by a gradual increase after 10 medications. Although patient age and race/ethnicity were not associated with synchronization, there was a significant positive association of receipt of a low-income subsidy and residence in rural areas with synchronization.

Conclusions: There is a complex relationship between refill synchronization and number of prescribed medications, and future research into synchronization should account for this.

Disclosures: This study was supported by the National Institute on Minority Health and Health Disparities under grant R01 MD010728. The authors have nothing to disclose. This study was presented as an oral abstract at the Society of General Internal Medicine Meeting; April 13, 2018; Denver, CO.