Racial and ethnic disparities in rifaximin use and subspecialty referrals for patients with hepatic encephalopathy in the United States.

BACKGROUND & AIMS: Rifaximin use in combination with lactulose is associated with a decreased risk of overt hepatic encephalopathy (HE). We sought to determine whether race and ethnicity were associated with rifaximin prescriptions. METHODS: We examined data for a 20% random sample of United States Medicare enrollees with cirrhosis and hepatic encephalopathy treated with outpatient lactulose and Part D prescription coverage from 2011-2019. Beginning at the time of first diagnosis, we evaluated time to first prescription of rifaximin accounting for competing risks (Fine-Gray, yielding subdistribution hazard ratios [sHRs]) and cumulative rifaximin exposure using a gamma hurdle model (yielding exposure length ratios). We aimed to determine the association of race and ethnicity with each outcome, adjusting for demographics, clinical factors, and other features of clinical management. RESULTS: Overall, 29,095 patients were diagnosed with HE and treated with lactulose, of whom 13,272 were prescribed rifaximin. Compared to White patients, Black patients were least likely to receive any prescription for rifaximin (sHR 0.70; 95% CI 0.65-0.76). Asian and Hispanic patients were also less likely to receive rifaximin compared to White patients. Black patients also received fewer doses of rifaximin (exposure length ratio 0.90; 95% CI 0.82-0.98). Hispanic patients also received fewer doses (0.88; 95% CI 0.80-0.98). Out-of-pocket spending on rifaximin per person-year was higher for Black and Hispanic than White patients. Out-of-pocket medication spending was associated with reduced odds of filling a rifaximin prescription. Black and Hispanic patients were least likely to be referred to a gastroenterologist. CONCLUSION: In a national cohort of patients with HE, we observed stark racial and ethnic disparities in the use of rifaximin, an approved therapy for the improvement of HE-specific outcomes. Access to gastroenterologists and cost controls may reduce disparities. LAY SUMMARY: Hepatic encephalopathy is a serious problem that can affect people with cirrhosis. When someone develops hepatic encephalopathy, there are 2 main treatments. The first-line treatment is called lactulose. If episodes of hepatic encephalopathy happen on lactulose, another treatment called rifaximin is recommended. In this study, we found that compared to White patients, Black and Hispanic patients are less likely to be prescribed rifaximin, receive fewer rifaximin refills, spend more on rifaximin, and have less access to subspecialists who are familiar with rifaximin. We conclude that efforts to address the cost of rifaximin and access to gastroenterologists could help improve these disparities.