The 2026 American College of Gastroenterology (ACG) Practice Guideline on Hepatic Encephalopathy recommends rifaximin at the U.S. Food and Drug Administration-approved dose of 550 mg twice daily to reduce the risk of recurrent overt hepatic encephalopathy in adults. The guideline notes that evidence supporting this recommendation includes a randomized controlled trial in which rifaximin 550 mg twice daily, administered for 6 months primarily in combination with lactulose, reduced the risk of breakthrough overt hepatic encephalopathy by 58% and hepatic encephalopathy-related hospitalization by 50% compared with placebo. Additional systematic review and meta-analysis data, as well as post hoc and observational studies, further support the use of rifaximin, particularly in combination with lactulose, for secondary prevention. [1]
The European Association for the Study of the Liver (EASL) 2022 guidelines for the management of hepatic encephalopathy recommends rifaximin as an adjunct to lactulose if secondary prophylaxis is indicated to prevent recurrent episodes. A dose recommendation is not provided. However, the guideline discusses evidence supporting rifaximin 600 mg twice daily in a separate clinical setting (Table 1). Specifically, it cites a large randomized, double-blind, placebo-controlled trial in patients with cirrhosis undergoing transjugular intrahepatic portosystemic shunt (TIPS), in which rifaximin 600 mg twice daily, initiated 14 days before TIPS and continued for approximately 6 months, significantly reduced the incidence of overt hepatic encephalopathy over 168 days compared with placebo (34% vs. 53%). The guideline notes that the potential benefit of continuing rifaximin beyond 6 months after TIPS remains unknown. The Japanese Society of Gastroenterology (JSGE) 2020 third guideline update for liver cirrhosis also recommends rifaximin as a standard treatment for hepatic encephalopathy, although it does not provide dose recommendations. Both the EASL and JSGE guidelines acknowledge limitations in the quality of evidence supporting rifaximin as first-line therapy, although this had a small or no effect on their recommendations. [2], [3]
A 2024 network meta-analysis explored the preventive and therapeutic effects of rifaximin on hepatic encephalopathy (HE) across different stages of the condition, utilizing varying dosages and strategies. The meta-analysis assimilated data from 21 studies and assessed outcomes such as HE incidence and progression, HE reversal, mortality, and adverse effects. The findings of this comprehensive meta-analysis demonstrate that rifaximin significantly reduces the incidence of HE in primary prevention (OR: 0.66; 95% CI: 0.45, 0.96; p=0.032) and is particularly effective in reducing the risk of recurrence in patients in remission (OR: 0.38; 95% CI: 0.28, 0.52; p<0.001). In patients with minimal HE, rifaximin decreased the transition to overt HE (OR: 0.17; 95% CI: 0.04, 0.63; p=0.008) and improved clinical symptoms in both minimal and overt HE cases (OR: 3.76; 95% CI: 2.69, 5.25; p<0.001). However, rifaximin did not demonstrate a reduction in mortality at any HE stage (OR: 0.79; 95% CI: 0.58, 1.08; p=0.133) and did not increase adverse effects (OR: 0.96; 95% CI: 0.74, 1.24; p=0.749). The network analysis revealed that a dosage of 400 mg t.i.d. ranked among the more favorable dosing strategies for both primary (surface under the cumulative ranking curve [SUCRA]: 0.87) and secondary prevention (SUCRA: 0.62) of HE, while a 600 mg b.i.d. dose ranked among the more favorable strategies for preventing progression from minimal to overt HE (SUCRA: 0.82) and for reversing minimal HE (SUCRA: 0.743), although it was not evaluated for the treatment of overt HE. [4]
A 2023 Cochrane systematic review and a 2012 meta-analysis also evaluated the efficacy and safety of rifaximin across a range of HE populations and dosing regimens.The 2012 meta-analysis included 12 randomized controlled trials (565 patients) and found that rifaximin was as effective as non-absorbable disaccharides and other oral antibiotics in improving clinical symptoms of HE, while being associated with significantly fewer adverse effects, particularly severe diarrhea. Although reductions in serum ammonia were similar between treatment groups, rifaximin demonstrated greater improvement in psychometric outcomes, including electroencephalographic changes and portosystemic encephalopathy grades. Most included studies used rifaximin 1200 mg/day in three divided doses (400 mg t.i.d.), with some studies administering 1100 mg/day in two divided doses (550 mg b.i.d.). The 2023 Cochrane review included 41 randomized trials (4,545 participants) and found that rifaximin likely improves HE compared with placebo or no intervention, particularly in patients with minimal HE and when used for prevention, but showed little overall difference compared with non-absorbable disaccharides alone. In contrast, rifaximin combined with a non-absorbable disaccharide likely reduced mortality, serious adverse events, HE recurrence, and hospital length of stay compared with a non-absorbable disaccharide alone. Across the included studies, rifaximin doses generally ranged from 1100 to 1200 mg/day depending on the clinical setting, with most acute, chronic, and primary prophylaxis studies using 1200 mg/day (typically 400 mg t.i.d.), whereas secondary prophylaxis studies used doses ranging from 800 to 1200 mg/day (median 1100 mg/day, commonly administered as 550 mg b.i.d.). Despite these favorable findings, the review concluded that the certainty of evidence ranged from very low to moderate, highlighting the need for additional high-quality trials. [5], [6]
A 2008 systematic review investigated the use of rifaximin for the treatment of hepatic encephalopathy. Included trials compared rifaximin with placebo, other antimicrobials, and nonabsorbable disaccharides. Many of the trials were randomized, double-blind, and enrolled patients with grade 1-3 hepatic encephalopathy according to the West Haven grading scale for mental state. The treatment regimen commonly consisted of rifaximin 400 mg three times daily (1,200 mg/day) with or without lactulose to cause 2 to 3 bowel movements/day. Overall, the clinical trials suggest rifaximin is effective in treating patients with cirrhosis and mild-to-moderate severity hepatic encephalopathy, with response rates ranging from 80 to 90%. Rifaximin was also associated with less tolerance issues and lower rates of hospitalization. However, primary outcome measures varied greatly between studies and sometimes failed to clearly define the efficacy criteria of treatment. See Table 2 for the authors’ summary of clinical trials. [7]
A 2013 meta-analysis (N= 8 randomized controlled trials; 407 patients) evaluated the efficacy and safety of rifaximin compared with nonabsorbable disaccharides for the treatment of hepatic encephalopathy. The dose of rifaximin was noted to typically be 1,200 mg/day in the included studies. The efficacy of rifaximin was found to be similar to that of nonabsorbable disaccharides (risk ratio [RR] 1.06; 95% confidence interval [CI] 0.94 to 1.19; p= 0.34). Rifaximin treatment was associated with improved serum ammonia levels, mental status, asterixis, and electroencephalogram response; however, these differences were not statistically significant. A significant difference was seen for grades of portosystemic encephalopathy (weighted mean difference [WMD] -2.3; 95% CI -2.78 to -1.82; p<0.00001). In terms of safety, pooled analysis for the incidence of severe diarrhea and abdominal pain indicated that rifaximin had lower rates of these adverse events (RR 0.19; 95% CI 0.1 to 0.37; p<0.00001). Overall, rifaximin was shown to be at least as effective as nonabsorbable disaccharides, with an improved safety profile. [8]