1875. How Many Different Antimicrobial Regimens Are There and Which Are Emerging and Declining?

BACKGROUND: Antimicrobial regimens evolve with changing recommendations and emerging practice patterns. We sought to explore the diversity of these patterns and to identify which inpatient regimens may be emerging in US Veterans Affairs medical centers (VAMC). METHODS: We extracted antimicrobial use and admission data from all acute care VA medical centers between 2005 and 2016. A regimen was defined as all unique antimicrobials and their routes given in a day to a single patient. We applied smoothing to account for intended discontinuation and intermittent dosing due to clearance. We described the distribution of regimens among VAMCs using the Gini index (a Gini index of 0 would mean all regimens were equally frequent and 1 would mean that one regimen dominated all others). We calculated the rank percentile of all regimens. We also used the absolute change in rank percentile between years 2005 and 2016 of the regimen used to describe emerging and declining regimens. RESULTS: There were 55,767 distinct regimens. Table 1 describes the Gini index and its decomposition among VAMCs. Overlap accounts for most of the inequality present because regimens are shared between VAMCs. Approximately 20% of the inequality present can be accounted for by variation between VAMCs. Table 2 describes the top 10 rising and the top 10 declining regimens. [Image: see text] [Image: see text] CONCLUSION: While there was a large number of distinct regimens, there was a relative handful of antimicrobial regimens dominated—most of which were commonly present among VAMCs (as manifest by the Gini “overlap” percent). Most regimens in the top 10 were broad-spectrum IV agents, with PO levofloxacin and doxycycline being notable standouts. IV vancomycin, which was the single most common regimen in 2005, decreased markedly. Linezolid and mixed PO metronidazole agents appear to be on the decline. DISCLOSURES: V. Stevens, Pfizer, Inc.: Grant Investigator, Research grant.