International variation in drug utilization: Antidepressant utilization in North America, Greece, and Ireland

Abstract

Background: Given significant regional differences globally in healthcare systems, policies, and culture, we examined rates of pharmaceutical utilization among four developed nations using antidepressant drugs as a case example. Materials and Methods: We conducted a population-based cross-sectional time series analysis of antidepressant utilization in Canada, the United States, Greece, and Ireland from January 2007 to September 2011 using data from IMS Healthcare Inc., which tracks over 80% of global prescription sales of over 1.3 million products. We studied 23 antidepressants from five drug classes, namely, 1) serotonin-specific reuptake inhibitors (SSRIs), 2) serotonin-norepinephrine reuptake inhibitors (SNRIs), 3) tricyclic antidepressants (TCAs), 4) monoamine oxidase inhibitors (MAOIs), and 5) 'other' antidepressants. We used time series analysis to examine trends in utilization patterns. Results: Overall antidepressant utilization increased steadily over time for all study regions, although regions differed considerably in the magnitude of antidepressant utilization and the rates of increase. While overall antidepressant utilization rates were similar between Canada (2,876 units per 1,000 population per month) and the United States (2,815 units per 1,000 population per month), these rates were approximately 83% higher than in Greece (1,558 units per 1,000 population per month) and approximately 50% higher than in Ireland (1,898 units per 1,000 population per month). Although the use of SSRIs, SNRIs, and other antidepressants generally increased over time, the use of TCAs and MAOIs generally decreased over time. Utilization of specific drug classes varied widely between regions, ranging from an 80% relative difference in SSRI utilization between the United States and Greece to a nearly 700% difference in the utilization of MAOIs between Canada and the United States. Conclusions: The findings of our study, using antidepressants as the case example, are consistent with previous studies demonstrating significant variation in drug utilization levels internationally. Future studies are needed to document regional variation in light of appropriateness of drug therapies to determine optimal utilization levels for maximal societal benefit.