Compliance after switching from branded to generic statins

Abstract

Purpose: The purpose of this study was to evaluate the impact of switching from branded to generic statins on medication compliance.

Methods: In this historic cohort study, we identified patients taking branded statins between January 2003 and December 2012 from Sutter Health's electronic health records in Northern California. Patients with ≥2 consecutive pharmacy claims for generic statins after initiating branded statins were classified as switchers. Switchers and non-switchers were matched 1:1 on the propensity for switching. Medication possession ratio (MPR) was calculated as the sum of days supply of therapy divided by treatment duration. We assessed between-group differences in compliance (MPR ≥ 0.80) by logistic regression.

Results: Among 16,364 patients meeting eligibility criteria, 8470 were retained in the matched cohort. No significant differences in compliance with statin therapy were observed for non-switchers versus switchers, overall, or versus patients switched from a branded to generic statin of the same agent (generic substitutions). Patients switched from a branded to generic statin of a different agent (therapeutic substitutions) more frequently received less potent statin dosing relative to those with generic substitutions (42.2% vs. <2%, respectively) and were significantly less compliant with statin therapy in the first 6 months after switching (73.9% vs. 77.6%; p = 0.011); however, compliance significantly improved among patients with therapeutic substitutions relative to generic substitutions more than 12 months after switching (66.2% vs. 61.3%; p = 0.021).

Conclusions: Compliance with statin therapy was largely similar among patients who switch to generic statins and those remaining on branded statins. Dosing should be reviewed when changing therapy to optimize clinical outcomes.

Keywords: compliance; drug interchange; generics; pharmacoepidemiology; statins.