Changes in Outpatient Use of Antibiotics by Adults in the United States, 2006–2015

Introduction: Numerous initiatives over the past decade have targeted the problem of antibiotic overuse in the US; however, the cumulative impact of such initiatives upon recent patterns of use is not known. Objectives: The aims of this study were to (1) describe general trends in outpatient antibiotic use among adults over the period 2006–2015; and (2) identify rapid shifts in use during this time period as potential indicators for key events. Methods: This was an observational study set in the ambulatory setting. Patients ≥ 18 years of age were selected from the Optum Clinformatics Datamart™, a commercial insurance claims database. The outcome measures of interest were prescriptions filled/1000 enrolled individuals, by year or quarter. We used linear regression to identify trends in use over multiple years, and change-point regression to identify rapid shifts in use within individual years. Results: From 2006 to 2015, antibiotic use declined significantly, decreasing by 12% for adults younger than 65 years of age (913–807 prescriptions/1000 individuals, p = 0.0001) and by 5% for adults ≥ 65 years of age (991–943 prescriptions/1000 individuals, p = 0.018). With change-point regression, we identified a number of rapid shifts in the use of specific antibiotic classes, such as downward shifts in the use of quinolones and macrolides during the second quarter of 2008 and 2013, respectively. Conclusions: Over the period 2006–2015 outpatient use of antibiotics decreased substantially among adults. Rapid shifts in use occurring in 2008 and 2013 may reflect the presence of key drivers of change, such as abrupt changes in access to care or perceived antibiotic safety.