Variation in the prescription drugs covered by health systems across high-income countries: A review of and recommendations for the academic literature.
BACKGROUND
Because not all medicines are equally safe, effective, and affordable, health systems often use formularies to define explicitly which medicines will be included and excluded from coverage.


OBJECTIVE
We sought to synthesize methods and findings from published studies of formulary variation across health systems in high-income countries.


METHODS
We conducted a systematic review of peer-reviewed research papers published from 2000 to 2017, inclusively. Because of the heterogeneous nature of the literature, we used an inductive approach to summarize methods and findings.


RESULTS
Nine studies met our study inclusion criteria. Included studies used a variety of methods for selecting medicines for analysis, for measuring coverage levels, and for measuring concordance between formularies. Studies assessing variations in coverage of all licensed medicines and found lower rates of cross-national coverage variation than studies of coverage for selected specialty drugs and indications. The one study that focused on coverage of high-volume medicines found the most complete and consistent levels of formulary listings across countries.


CONCLUSION
Although published studies contain interesting findings that likely have prompted discussions about their policy implications, the literature can be improved with greater transparency concerning the overarching objective of work in this area and more rigor concerning the selection, analysis, and reporting of data.