OBJECTIVES

: To assess the pattern and quality of prescribing using Formulary Selectivity Index (FSI) and to measure drug dispersion using Herfindahl-Hirschman Index (HHI)

METHODS

: We retrieved prescription data from electronic health record across four institutions: Brigham and Women’s Hospital (BWH), Northwestern Medicine (NM), University of Illinois (UIC) and Veterans Administration (VA). We calculated the FSI as the Gini coefficient, the value for FSI ranges from 0 (“No selectivity”) to 1 (“complete selectivity”). We also calculated HHI as the sum of the square of the drug share, with value are divided from <0.2 (Competitively dispersed), 0.2-0.6 (Moderately dispersed) and >0.6 (Highly dispersed). The two indices were normalized to allow comparison between drug classes with variable number of drugs.

RESULTS

: The research included 4655 Primary Care Physicians (PCPs) and 4 930 707 patients written to an adult patient population from January 1, 2017, to December 31, 2018 for 15 drug classes. PCPS were more selective when prescribing ACE inhibitors (FSI: 0.90-0.97; HHI: 0.66-0.90) and least selective when prescribing SSRIs (FSI: 0.59-0.67). Drugs were competitively dispersed (HHI: 0.11-0.2) in Injectibles used in the treatment of Diabetes Mellitus. PCPs of UIC were most selective when compared to other three centers. Opioids drug class had more number of drugs (18) in its basket, primary drugs being Tramadol, Oxycodone and Hydrocodone.

CONCLUSIONS

: The findings show differences in prescribing among PCPs across four centers, with more selective use within classes of ACE inhibitors and ARBs than other commonly prescribed drugs.