Abstract

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 was 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.