Growing racial/ethnic disparities in buprenorphine distribution in the United States, 2007-2017

Objective: To assess whether per capita buprenorphine distribution varies by regional racial/ethnic composition, Medicaid expansion status, and time period. Methods: Our unit of analysis-three-digit ZIP codes (ZIP3s)-was classified into quintiles based on percentage of White residents. A weighted linear regression model of buprenorphine distribution-including White resident quintile, waivered prescriber rate, overdose rate, sociodemographic factors, and year fixed effects-was estimated using national buprenorphine distribution data from 2007 to 2017. We report predictive margins of the buprenorphine distribution rate by quintile, as well as average marginal effects of waivered prescriber rate on buprenorphine distribution rate for each quintile. Analyses were stratified by Medicaid expansion status and time period (2007-2010, 2011-2014, 2015-2017). Results: Buprenorphine distribution increased nationally during 2007-2017, yet growth was disproportionately greater for ZIP3s with higher percentages of White residents. Medicaid expansion states exhibited significant differences in buprenorphine distribution across ZIP3 quintiles during 2007-2010, the magnitude of which increased across time periods. Non-expansion states exhibited significant quintile differences during 2011-2014 and 2015-2017. The average marginal effect of increasing the waivered prescriber rate on the distribution rate was consistently smaller in ZIP3s with lower percentages of White residents, particularly in expansion states. Conclusions: We find ecological evidence consistent with racial/ethnic disparities in buprenorphine distribution. Our finding that increasing the waivered prescriber rate had differential effects by ZIP3 racial/ethnic composition suggest that broad initiatives to increase the number of waivered prescribers are likely insufficient to achieve equitable buprenorphine access. Rather, targeted and tailored policy efforts are warranted.

Automated summary

The study found that buprenorphine distribution increased nationally from 2007 to 2017, with disproportionately greater growth in ZIP3s with higher percentages of White residents. Medicaid expansion states showed significant differences in buprenorphine distribution across ZIP3 quintiles during 2007-2010, and the differences increased over time periods. Non-expansion states exhibited significant quintile differences during 2011-2014 and 2015-2017.