To describe patterns of outpatient antibacterial use among California Medicaid (Medi-Cal) fee-for-service system beneficiaries, and to investigate the influence of demographic factors—age, race-ethnicity, state county, and population density—on those patterns.
Retrospective analysis of administrative claims data.
Medi-Cal fee-for-service system claims database.
All outpatient Medi-Cal fee-for-service system beneficiaries enrolled between 2006 and 2011 who had at least one systemic antibacterial claim.
MEASUREMENTS AND MAIN RESULTS
Rates of antibacterial prescribing and the proportion of broad-spectrum antibacterial use were measured over the study period and among age, racial-ethnic and geographic (county) groups. Of the 10,018,066 systemic antibacterial claims selected for analysis, antibacterial prescribing rates decreased from 542 claims/1000 beneficiaries in 2006 to 461 claims/1000 beneficiaries in 2011 (r = –0.971, p = 0.0012; τ-b = –1.00, p = 0.009). Among age groups, children had the highest rate of use (605 claims/1000 beneficiaries, χ2 (2) = 320,000, p < 0.001); among racial-ethnic groups, Alaskan Natives and Native Americans had the highest rate of use (1086/1000 beneficiaries, χ2 (5) = 197,000, p < 0.001). Broad-spectrum antibacterial prescribing increased from 28.1% (95% confidence interval [CI] 28.1–28.2%) to 32.7% (95% CI 32.6–32.8%) over the study period. Senior age groups and Caucasians received the highest proportions of broad-spectrum agents (53.4% [95% CI 52.5–54.3%] and 36.6% [95% CI 36.6–36.7%], respectively). Population density was inversely related to both overall antibacterial use (ρ = –0.432, p = 0.0018) and broad-spectrum antibacterial prescribing (ρ = –0.359, p < 0.001). The rate of prescribing decreased over the study period for all antibacterial classes with the exception of macrolides and sulfonamides. Amoxicillin was the most frequently prescribed agent.
Overall and broad-spectrum antibacterial use in the Medi-Cal fee-for-service program are less than that observed nationally. Significant variations in prescribing exist between age and racial-ethnic groups, and heavily populated areas are associated with both less antibacterial use and less broad-spectrum antibacterial prescribing. Studies are needed to determine the reasons for the observed differences in antibacterial use among demographic groups.