The potential for development of clinically relevant microbial resistance to rifaximin-α: a narrative review.

Rifaximin-α is a gut-targeted antibiotic indicated for numerous gastrointestinal and liver diseases. Its multifaceted mechanism of action goes beyond direct antimicrobial effects, including alterations in bacterial virulence, cytoprotective effects on host epithelial cells, improvement of impaired intestinal permeability, and reduction of proinflammatory cytokine expression via activation of the pregnane X receptor. Rifaximin-α is virtually non-absorbed, with low systemic drug levels contributing to its excellent safety profile. While there are high concentrations of drug in the colon, low water solubility leads to low colonic drug bioavailability, protecting the gut microbiome. Rifaximin-α appears to be more active in the bile-rich small bowel. Its important biologic effects are largely at sub-inhibitory concentration. Although in vitro testing of clinical isolates from rifaximin recipients has revealed rifaximin-resistant strains in some studies, the risk of emergent rifaximin-α resistance appears to be lower than for many other antibiotics. Rifaximin-α has been used for many years for traveler's diarrhea with no apparent increase in resistance levels in causative pathogens. Further, rifaximin-α retains its efficacy after long-term and recurrent usage in chronic gastrointestinal disorders. There are numerous reasons why the risk of microbial resistance to rifaximin-α may be lower than that for other agents, including low intestinal bioavailability in the aqueous colon, the mechanisms of action of rifaximin-α not requiring inhibitory concentrations of drug, and the low risk of cross transmission of rifaximin-α resistance between bacterial species. Reported emergence of vancomycin-resistant Enterococcus in liver-disease patients maintained on rifaximin needs to be actively studied. Further studies are required to assess the possible correlation between in vitro resistance and rifaximin-α efficacy.

Improved cognition after rifaximin treatment is associated with changes in intra- and inter-brain network functional connectivity.

BACKGROUND: Rifaximin is a non-reabsorbable antibiotic which acts at gut level, and improves cognition and inflammatory parameters in minimal hepatic encephalopathy (MHE) patients, but not all patients show the same level of response. This study aims to assess brain activity, both within and between brain networks, following rifaximin treatment, considering the differences between response groups as well. METHODS: Twenty-two healthy controls and 53 patients with cirrhosis (22 without and 31 with MHE, diagnosed by Psychometric Hepatic Encephalopathy Score, PHES) performed psychometric, attention and coordination tests, and blood inflammatory parameters were measured. Resting-state functional magnetic resonance imaging (fMRI) acquisitions were performed on controls and MHE patients. Eighteen MHE patients underwent a rifaximin treatment for 6 months, after which all measures were repeated. fMRI images were analysed and changes after treatment were assessed. RESULTS: After rifaximin treatment, 13 patients improved their PHES score (Responder patients) while 5 did not (Non-responder patients). No significant decrease in blood ammonia was observed after rifaximin treatment, but there was a decrease in plasma inflammatory cytokines in responder patients. A global effect of rifaximin was detected on the sensorimotor and fronto-parietal networks. Responder patients showed a relative increase of thalamic network connectivity in comparison to non-responder patients. Before treatment, responder and non-responder patients showed connectivity differences in basal ganglia network. The connection of the sensorimotor and thalamic networks between them and with other networks suffered changes after treatment. These connections between networks mostly decreased after treatment. All changes and differences showed a significant level of correlation with the performance of psychometric tests and the blood levels of inflammatory biomarkers. CONCLUSIONS: There was an improvement of the communication between executive, motor and attention-related brain areas, and their functional independence following rifaximin treatment. Patients who respond also show a less deteriorated connection involved in these functions before treatment. Results suggest that the improved inflammatory state of MHE patients, following rifaximin treatment would favour the observed changes in brain function and enhanced cognitive performance.

Therapeutic potential and mechanisms of Rifaximin in ameliorating iron overload-induced ferroptosis and liver fibrosis in vivo and in vitro.

Liver fibrosis could progress to liver cirrhosis with several contributing factors, one being iron overload which triggers ferroptosis, a form of regulated cell death. Rifaximin, a non-absorbable antibiotic, has shown promise in mitigating fibrosis, primarily by modulating gut microbiota. This study investigated the effects and mechanisms of rifaximin on iron overload-related hepatic fibrosis and ferroptosis. In an iron overload-induced liver fibrosis model in mice and in ferric ammonium citrate (FAC)-stimulated primary hepatocytes, treatment with rifaximin showed significant therapeutic effects. Specifically, it ameliorated the processes of ferroptosis triggered by iron overload, reduced liver injury, and alleviated fibrosis. This was demonstrated by decreased iron accumulation in the liver, improved liver function, and reduced fibrotic area and collagen deposition. Rifaximin also modulated key proteins related to iron homeostasis and ferroptosis, including reduced expression of TFR1, a protein facilitating cellular iron uptake, and increased expression of Fpn and FTH, proteins involved in iron export and storage. In the context of oxidative stress, rifaximin treatment led to a decrease in lipid peroxidation, evidenced by reduced levels of reactive oxygen species (ROS) and malondialdehyde (MDA), and an increase in the reduced glutathione (GSH) and decrease in oxidized glutathione (GSSG). Notably, rifaximin's potential functions were associated with the TGF-ß pathway, evidenced by suppressed Tgfb1 protein levels and ratios of phosphorylated to total Smad2 and Smad3, whereas increased Smad7 phosphorylation. These findings indicate rifaximin's therapeutic potential in managing liver fibrosis by modulating the TGF-ß pathway and reducing iron overload-induced damage. Further research is required to confirm these results and explore their clinical implications.

Emerging drugs for the treatment of sarcopenia in cirrhosis of the liver.

INTRODUCTION: Malnutrition and sarcopenia are common and impact the prognosis in patients with liver cirrhosis. The etiology is multifactorial and includes periods of reduced caloric intake, increased catabolism and direct molecular mechanisms that inhibit muscle synthesis. Although these conditions are widely acknowledged, and there is a growing interest in their diagnosis, robust evidence regarding the treatment and reversibility of these conditions is still lacking. AREAS COVERED: We have explored the current evidence on the pharmacological treatment of sarcopenia in patients with cirrhosis. Additionally, we have searched for drugs already in use and ongoing trials for other chronic diseases. EXPERT OPINION: The current guidelines recommend the use of a protein-adequate diet and moderate physical activity for treating sarcopenia in patients with cirrhosis. Currently, robust evidence is derived only from the supplementation of Branched-Chain Amino Acids, capable of increasing muscle mass and function. There are many drugs targeting various pathways that contribute to sarcopenia. However, evidence is sporadic and insufficient to suggest their use in clinical practice.Novel drugs specifically designed to enhance muscle mass and function should be developed. Finally, gender significantly influences the type of muscle alteration and therapeutic mechanisms; therefore, future studies should be designed taking gender differences into consideration.

Preventive and therapeutic effects of rifaximin on hepatic encephalopathy with differential application dosages and strategies: a network meta-analysis.

BACKGROUND: Hepatic encephalopathy (HE) is a neuropsychiatric syndrome that affects the prognosis of patients with liver disease and is considered an independent risk factor for hospitalization and death. Rifaximin has been approved for HE treatment. This review will analyze the effect of rifaximin on different stages of HE with differential application dosages and strategies by traditional and network meta-analyses. METHODS: We performed a systematic search of PubMed, EmBase, and Cochrane Library databases up to February 26, 2023, to identify randomized controlled trials (RCTs) about rifaximin for the prevention and treatment of HE. The outcomes included incidence of HE and HE progression, HE reversal, mortality, and adverse effects. RESULTS: A total of 21 studies were included. In the primary prevention of HE, rifaximin significantly reduced the incidence of HE (OR: 0.66; 95% CI: 0.45, 0.96; p = 0.032). In secondary prevention, rifaximin significantly reduced the risk of recurrence in patients who were in remission (OR: 0.38; 95% CI: 0.28, 0.52; p < 0.001). In the treatment of minimal HE, rifaximin significantly reduced the breakthrough of MHE to OHE (OR: 0.17; 95% CI: 0.04,0.63; p = 0.008). Rifaximin also significantly improved the clinical symptoms of MHE and OHE patients (OR: 3.76; 95% CI: 2.69, 5.25; p < 0.001). However, rifaximin did not reduce mortality at any stage in HE patients (OR: 0.79; 95% CI: 0.58, 1.08; p = 0.133). Additionally, rifaximin did not increase the risk of adverse effects (OR: 0.96; 95% CI: 0.74, 1.24; p = 0.749). In the network meta-analysis, the 400 mg T.I.D. intervention had a relative advantage for HE risks in primary and secondary prevention. In the treatment of MHE, 600 mg b.i.d. was superior in preventing the breakthrough from MHE to OHE. CONCLUSION: Rifaximin prevented HE risks and progression and improved clinical symptoms in patients with MHE but did not reduce mortality. For primary and secondary prevention, 400 mg t.i.d. could be considered. 600 mg b.i.d. could be considered in patients with MHE.

Rifaximin treatment shapes a unique metagenome-metabolism network in patients with decompensated cirrhosis.

BACKGROUND: Patients with decompensated cirrhosis face poor prognosis and increased mortality risk. Rifaximin, a non-absorbable antibiotic, has been shown to have beneficial effects in preventing complications and improving survival in these patients. However, the underlying mechanisms of rifaximin's effects remain unclear. METHODS: We obtained fecal samples from decompensated cirrhotic patients undergoing rifaximin treatment and controls, both at baseline and after 6 months of treatment. Shotgun metagenome sequencing profiled the gut microbiome, and untargeted metabolomics analyzed fecal metabolites. Linear discriminant and partial least squares discrimination analyses were used to identify differing species and metabolites between rifaximin-treated patients and controls. RESULTS: Forty-two patients were enrolled and divided into two groups (26 patients in the rifaximin group and 16 patients in the control group). The gut microbiome's beta diversity changed in the rifaximin group but remained unaffected in the control group. We observed 44 species with reduced abundance in the rifaximin group, including Streptococcus_salivarius, Streptococcus_vestibularis, Haemophilus_parainfluenzae, etc. compared to only four in the control group. Additionally, six species were enriched in the rifaximin group, including Eubacterium_sp._CAG:248, Prevotella_sp._CAG:604, etc., and 14 in the control group. Furthermore, rifaximin modulated different microbial functions compared to the control. Seventeen microbiome-related metabolites were altered due to rifaximin, while six were altered in the control group. CONCLUSION: Our study revealed distinct microbiome-metabolite networks regulated by rifaximin intervention in patients with decompensated cirrhosis. These findings suggest that targeting these specific metabolites or related bacteria might be a potential therapeutic strategy for decompensated cirrhosis.

Rifaximin and alternative agents in the management of irritable bowel syndrome: A comprehensive review.

Rifaximin, a broad-spectrum antibiotic, boasts a unique chemical composition and pharmacokinetic profile, rendering it highly effective in treating irritable bowel syndrome (IBS). Its minimal systemic absorption confines its impact to the gastrointestinal (GI) tract, where it yields significant therapeutic benefits. This review examines rifaximin's physico-chemical attributes and its role in managing IBS symptoms. Its molecular structure facilitates intestinal lumen retention postoral administration, minimizing systemic exposure and adverse effects. This targeted action is crucial in addressing the gut microbiota's role in IBS pathophysiology. By modifying microbial populations and their metabolite production, rifaximin mitigates symptoms like bloating, irregular bowel habits, and abdominal pain associated with IBS. It achieves this by reducing pathogenic bacteria and altering bacterial metabolism, enhancing mucosal and immune function. Clinical trials affirm rifaximin's superiority over placebo and conventional therapies in alleviating overall IBS symptoms and addressing small intestine bacterial overgrowth (SIBO). Despite its promising efficacy and sustained symptom relief, further research is essential to optimize long-term effectiveness and dosing regimens. Rifaximin stands as a vital treatment option for IBS due to its distinctive properties and clinical utility; yet, ongoing investigation is imperative for maximizing its therapeutic benefits.

Effectiveness of rifaximin and probiotics for the correction of intestinal permeability in patients with metabolic-associated fatty liver disease in combination with type 2 diabetes mellitus.

OBJECTIVE: Aim: To investigate the effectiveness of rifaximin and probiotics for the correction of intestinal permeability in patients with metabolic-associated fatty liver disease (MAFLD) in combination with type 2 diabetes mellitus. PATIENTS AND METHODS: Materials and Methods: The prospective interventional randomized investigation included 68 patients with MAFLD in combination with type 2 diabetes, who were examined and divided into the 2 groups of treatment. RESULTS: Results: The serum levels of interleukin (IL) - 6, IL-10 and zonulin, indicators of liver functional activity, liver attenuation coefficient between treatment group vs. control group after 2 weeks, 1 month, 3 and 6 months of therapy were significant differed. The serum levels of IL-6 and zonulin significantly decreasing and increasing of IL-10 in the treatment group after 2 weeks, 1, 3 and 6 months of combined therapy. When comparing of stool short-chain fatty acids concentration between treatment group vs. control group after 2 weeks, 1 month, 3 and 6 months of therapy the levels of acetic, butyric and propionic acids significantly differences and increase in their levels were established. CONCLUSION: Conclusions: The results of the study in dynamics during 6 months show that the additional appointment of rifaximin, multispecies probiotic and prebiotic to metformin in patients with MAFLD and type 2 diabetes led to the elimination of subclinical inflammation, modulation of the permeability of the intestinal barrier and lowering increased intestinal permeability, as well as to the lower serum activity of liver aminotransferases and decrease the stage of steatosis.

Clearance and production of ammonia quantified in humans by constant ammonia infusion - the effects of cirrhosis and ammonia-targeting treatments.

BACKGROUND & AIMS: Hyperammonaemia is a key pathological feature of liver disease and the primary driver of hepatic encephalopathy (HE). However, the relative roles of increased ammonia production and reduced clearance are poorly understood as is the action of ammonia-targeting drugs for HE. We aimed to quantify whole-body ammonia metabolism in healthy persons and patients with cirrhosis and to validate our method by examining the effects of glycerol phenylbutyrate and lactulose + rifaximin treatment. METHODS: Ten healthy men and ten male patients with cirrhosis were investigated by 90-minute constant ammonia infusion to achieve steady-state plasma ammonia. Whole-body ammonia clearance was calculated as infusion rate divided by steady-state concentration increase and ammonia production was calculated as clearance multiplied by baseline ammonia concentration. Participants were re-investigated after the ammonia-targeting interventions. RESULTS: In healthy persons, ammonia clearance was 3.5 (3.1-3.9) L/min and ammonia production was 49 (35-63) µmol/min. Phenylbutyrate increased clearance by 11% (4-19%, p = 0.009). In patients with cirrhosis, ammonia clearance was 20% lower at 2.7 (2.1-3.3) L/min (p = 0.02) and production was nearly threefold higher at 131 (102-159) µmol/min (p <0.0001). Lactulose + rifaximin reduced production by 20% (2-37%, p = 0.03). The infusion was generally well-tolerated apart from in one hyperammonaemic patient, with cirrhosis and possible bleeding unrelated to the infusion, who developed clinical HE that reverted when infusion was discontinued. CONCLUSIONS: Whole-body ammonia clearance and production may be measured separately using the described technique. This technique identified a lower clearance and a higher production of ammonia in patients with cirrhosis, and showed that phenylbutyrate increases clearance, whereas lactulose + rifaximin reduces production. IMPACT AND IMPLICATIONS: High blood ammonia plays a key role in cirrhosis-related brain dysfunction. However, the relative roles of reduced ammonia clearance and increased ammonia production are poorly understood as is the action of ammonia-targeting treatments. This study presents a relatively simple test to measure ammonia metabolism. By using this test, it was possible to show that patients with cirrhosis exhibit decreased ammonia clearance and increased ammonia production compared to healthy persons, and to quantify the unique effects of different ammonia-targeting treatments. The test described herein may be used to examine a range of questions related to normal physiology, pathophysiology and the mechanisms of action of ammonia-targeting treatments. CLINICAL TRIAL NUMBER: ClinicalTrials.gov (1-16-02-297-20).

Dosing of Rifaximin Soluble Solid Dispersion Tablets in Adults With Cirrhosis: 2 Randomized, Placebo-controlled Trials.

BACKGROUND & AIMS: Cirrhosis-related complications are a major burden. Rifaximin soluble solid dispersion (SSD) tablets (immediate-release [IR]; sustained extended-release [SER]) were designed to increase rifaximin water solubility. These analyses evaluate dosing for prevention of cirrhosis complication-related hospitalizations/mortality and overt hepatic encephalopathy (OHE) treatment. METHODS: Two phase II, randomized, double-blind, placebo-controlled trials were conducted. Trial 1: outpatients with early decompensated cirrhosis randomized to placebo or rifaximin SSD once-nightly: IR 40 or 80 mg, SER 40 or 80 mg, or IR 80 mg plus SER 80 mg, for 24 weeks. Trial 2: inpatients with OHE randomized to lactulose plus placebo or rifaximin SSD: IR 40 mg once or twice daily or SER 80 mg once or twice daily for ≤14 days. Primary efficacy endpoint: time to cirrhosis complication-related hospitalization/all-cause mortality (Trial 1) or time to OHE resolution (Trial 2). RESULTS: In Trial 1 (n = 516), no significant difference in time to cirrhosis complication-related hospitalization/all-cause mortality vs placebo. In a post hoc analysis, time to all-cause hospitalization/all-cause mortality was improved with IR 40 mg vs placebo (15.4% [12/78] vs 27.7% [26/94]; P = .03). A Trial 2 prespecified interim analysis (n = 71) showed lactulose plus rifaximin SSD IR 40 mg bid significantly reduced median time to OHE resolution (21.1 hours) vs lactulose plus placebo (62.7 hours; P = .02). Trial 2 was subsequently terminated. CONCLUSION: Rifaximin SSD IR 40 mg may reduce hospitalizations in patients with cirrhosis and shorten duration of OHE during hospitalization-considered a negative finding, yet also hypothesis-generating. (ClinicalTrials.govNCT01904409; NCT03515044).

AGA Clinical Practice Guideline on the Pharmacological Management of Irritable Bowel Syndrome With Diarrhea.

BACKGROUND & AIMS: Irritable bowel syndrome (IBS) is a common functional gastrointestinal disorder associated with significant disease burden. This American Gastroenterological Association Guideline is intended to support practitioners in decisions about the use of medications for the pharmacological management of IBS with predominant diarrhea (IBS-D) and is an update of a prior technical review and guideline. METHODS: The Grading of Recommendations Assessment, Development and Evaluation framework was used to assess evidence and make recommendations. The technical review panel prioritized clinical questions and outcomes according to their importance for clinicians and patients and conducted an evidence review of the following agents: eluxadoline, rifaximin, alosetron, loperamide, tricyclic antidepressants, selective serotonin reuptake inhibitors, and antispasmodics. The guideline panel reviewed the evidence and used the Evidence-to-Decision Framework to develop recommendations. CONCLUSIONS: The panel agreed on 8 recommendations for the management of patients with IBS-D. The panel made conditional recommendations for eluxadoline, rifaximin, alosetron, (moderate certainty), loperamide (very low certainty), tricyclic antidepressants, and anstispasmodics (low certainty). The panel made a conditional recommendation against the use of selective serotonin reuptake inhibitors (low certainty).

Modulation of the microbiota across different intestinal segments by Rifaximin in PI-IBS mice.

BACKGROUND: Rifaximin has been increasingly applied in irritable bowel syndrome (IBS) treatment. Whether there were differences in the effects of rifaximin on microbiota from different intestinal segments, especially the small intestine where rifaximin predominantly acted, has not been confirmed. METHODS: In this study, we used Trichinella spiralis infection to induce post infectious irritable bowel syndrome (PI-IBS) and measured visceral sensitivity of mice by means of abdominal withdrawal reflex (AWR) tests to colorectal distention (CRD). We compared the effects of rifaximin on the composition of ileal, colonic mucosal and fecal microbiota in PI-IBS mice. RESULTS: Rifaximin significantly reduced AWR scores and increased pain threshold in PI-IBS mice, and this effect was associated with the change in the relative abundance of ileal mucosal microbiota. Rifaximin could obviously decrease ileum mucosal microbiota alpha diversity assessed by Shannon microbial diversity index. Meanwhile, the analysis of beta diversity and relative abundance of microbiota at phylum, family and genus levels showed that rifaximin could improve the microbiota structure of ileal mucosa. However, for colonic mucosal and fecal microbiota, this effect of rifaximin was not obvious. Rifaximin could reshape the correlation of genera between different intestinal segments. CONCLUSION: Rifaximin improved visceral hypersensitivity in PI-IBS mice. Rifaximin mainly affected ileal mucosal microbiota, and its improvement effect on IBS might be closely related to the improvement of ileal microbiota structure.

Working Memory in Patients with Varying Degree of Hepatic Encephalopathy (HE): A Pilot EEG-fNIRS Study.

It is known that patients with covert hepatic encephalopathy (CHE) exhibit working memory abnormalities, but to date there is no study comparing patients with cirrhosis with/without CHE and controls with both electrophysiological and hemodynamic data collected at the same time.Here we collected behavioral [accuracy and reaction times (RTs), electrophysiological (evoked potentials) and hemodynamic (oxygenated and deoxygenated haemoglobin) correlates of an n-back task [formed by a control (0-back) condition, a low (1-back) and a high (2-back) working memory load conditions] in patients with cirrhosis with/without CHE: (1) at baseline (n = 21, males = 15, 58±8 yrs), and by comparison with controls (n = 21, males = 15, 57±11 yrs) and (2) after a 3-month course of rifaximin (n = 18, males = 12, 61±11 yrs), and by comparison to baseline.All patients showed slower RTs (p < 0.0001) and lower P2 amplitude compared with controls (p = 0.018); moreover, patients with CHE showed reduced accuracy (p < 0.0001) compared with controls, and patients without CHE showed higher oxygenated haemoglobin in the central dorsolateral prefrontal cortex in the 2-back compared with patients with CHE. Post-rifaximin, oxygenated haemoglobin increased in the central frontopolar cortex. In addition, in patients without CHE the RTs of the 2-back became comparable to those of the 0-back and P3 showed higher amplitude.In conclusion, the presence of cirrhosis seemed to have more effects than CHE on working memory at baseline. A course of treatment with rifaximin was more beneficial to patients without CHE, who probably had more room for improvement in this complex task.

Active Clinical Trials in Hepatic Encephalopathy: Something Old, Something New and Something Borrowed.

Hepatic encephalopathy (HE) is a potentially reversible neurocognitive syndrome that occurs in patients with acute or chronic liver disease. Currently, most of the therapies for HE aim to reduce ammonia production or increase its elimination. To date, only two agents have been approved as treatments for HE: lactulose and rifaximin. Many other drugs have also been used, but data to support their use are limited, preliminary or lacking. The aim of this review is to provide an overview and discussion of the current development of treatments for HE. Data from ongoing clinical trials in HE were obtained from the ClinicalTrials.gov website, and a breakdown analysis of studies that were active on August 19th, 2022, was performed. Seventeen registered and ongoing clinical trials for therapeutics targeting HE were identified. More than 75% of these agents are in phase II (41.2%) or in phase III (34.7%). Among them, there are many old acquaintances in the field, such as lactulose and rifaximin, some new entries such as fecal microbiota transplantation and equine anti-thymocyte globulin, an immunosuppressive agent, but also some therapies borrowed from other conditions, such as rifamycin SV MMX and nitazoxanide, two antimicrobial agents FDA approved for the treatment of some types of diarrheas or VE303 and RBX7455, two microbiome restoration therapies, currently used as treatment of high-risk Clostridioides difficile infections. If working, some of these drugs could soon be used as valid alternatives to current therapies when ineffective or be approved as novel therapeutic approaches to improve the quality of life of HE patients.

Rifaximin stimulates nitrogen detoxification by PXR-independent mechanisms in human small intestinal organoids.

BACKGROUND AND AIMS: Recurrent hepatic encephalopathy (HE) is characterized by hyperammonaemia in combination with neuropsychiatric abnormalities and is treated with lactulose and rifaximin. Rifaximin is a pregnane X receptor (PXR) agonist with low systemic and high intestinal bioavailability. The mechanisms by which it alleviates HE are unclear. We used human small intestinal (hSI) organoids to study whether rifaximin, via PXR activation, affects the epithelial biotransformation machinery, and to gain understanding of its low systemic availability. METHODS: We generated PXR knockdown hSI organoids via lentiviral delivery of short hairpin RNAs. Organoids were cultured for 24 h with rifaximin or rifampicin. RNA-sequencing and metabolomics were performed to analyse gene expression and amino acid metabolism. Luminal rifaximin was quantified by photospectrometry. RESULTS: Treatment of wild-type hSI organoids with rifaximin resulted in >twofold differential expression of 131 genes compared to DMSO. These effects were largely PXR independent and related to amino acid metabolism. Rifaximin decreased expression of glutaminase-2 and increased expression of asparagine synthetase and solute carrier 7A11, thereby increasing intracellular glutamine and asparagine concentrations, indicating active ammonia detoxification. Rifaximin was apically excreted into the lumen in an ATP binding cassette B1 (ABCB1)-dependent manner. CONCLUSIONS: Rifaximin-after uptake into enterocytes-stimulates intracellular nitrogen detoxification by PXR-independent mechanisms. Active apical excretion of rifaximin by ABCB1 into the intestinal lumen explains its low systemic bioavailability. Our study implies that rifaximin, next to modulation of the microbiome, has direct effects on ammonia scavenging in the human small intestinal epithelium.

Eubiotic effect of rifaximin is associated with decreasing abdominal pain in symptomatic uncomplicated diverticular disease: results from an observational cohort study.

BACKGROUND: Rifaximin effectively treats symptomatic uncomplicated diverticular disease (SUDD) and has shown eubiotic potential (i.e., an increase in resident microbial elements with potential beneficial effects) in other diseases. This study investigated changes in the fecal microbiome of patients with SUDD after repeated monthly treatment with rifaximin and the association of these changes with the severity of abdominal pain. METHODS: This was a single-center, prospective, observational, uncontrolled cohort study. Patients received rifaximin 400 mg twice a day for 7 days per month for 6 months. Abdominal pain (assessed on a 4-point scale from 0 [no pain] to 3 [severe pain]) and fecal microbiome (assessed using 16 S rRNA gene sequencing) were assessed at inclusion (baseline) and 3 and 6 months. The Spearman's rank test analyzed the relationship between changes in the gut microbiome and the severity of abdominal pain. A p-value ≤ 0.05 was considered statistically significant. RESULTS: Of the 23 patients enrolled, 12 patients completed the study and were included in the analysis. Baseline abdominal pain levels decreased significantly after 3 (p = 0.036) and 6 (p = 0.008) months of treatment with rifaximin. The abundance of Akkermansia in the fecal microbiome was significantly higher at 3 (p = 0.017) and 6 (p = 0.015) months versus baseline. The abundance of Ruminococcaceae (p = 0.034), Veillonellaceae (p = 0.028), and Dialister (p = 0.036) were significantly increased at 6 months versus baseline, whereas Anaerostipes (p = 0.049) was significantly decreased. The severity of abdominal pain was negatively correlated with the abundance of Akkermansia (r=-0.482; p = 0.003) and Ruminococcaceae (r=-0.371; p = 0.026) but not with Veillonellaceae, Dialister, or Anaerostipes. After 3 months of rifaximin, abdominal pain was significantly less in patients with Akkermansia in their fecal microbiome than in patients without Akkermansia (p = 0.022). CONCLUSION: The eubiotic effect of rifaximin was associated with decreased abdominal pain in patients with SUDD.

Norfloxacin versus alternative antibiotics for prophylaxis of spontaneous bacteria peritonitis in cirrhosis: a systematic review and meta-analysis.

BACKGROUND: Spontaneous bacterial peritonitis (SBP) is a life-threatening complication in patients with advanced cirrhosis. Prophylactic Norfloxacin used to be considered effective in SBP prevention, but in recent years its efficacy has been partially compromised by increasing quinolone-resistant bacteria. However, whether the effects of alternative prophylactic regimens are superior to norfloxacin remains controversial. The goal of this study is to compare the effects of norfloxacin with other antibiotics in SBP prophylaxis for cirrhotic patients. METHODS: We systematically searched Pubmed, Embase, and Cochrane Library Databases. Two reviewers independently identified relevant random control trials (RCTs) comparing the role of norfloxacin and other antibiotics in SBP prevention. RESULTS: Eight studies comprising 1043 cirrhotic patients were included in this study. Norfloxacin and alternative antibiotics displayed comparable effects in SBP prophylaxis, survival benefit, overall infection prevention, and safety. Subgroup analyses revealed that rifaximin prophylaxis could reduce the recurrence of SBP with fewer adverse events but failed to improve overall survival compared with norfloxacin. CONCLUSIONS: Other antibiotics are a reasonable alternative to norfloxacin in the prophylaxis of SBP. Rifaximin prophylaxis could be an alternative choose of antibiotic for SBP prevention because of its better protective effect and safety.

Clinical Outcomes of Oral Zinc Therapy in Hepatic Encephalopathy Treatment.

BACKGROUND: Additional therapies for hepatic encephalopathy (HE) treatment are warranted. There are data evaluating the use of zinc for HE; however, clinical outcomes, specifically in the United States, are unknown. OBJECTIVE: To compare 30-day and 1-year all-cause readmission rates in patients with cirrhosis complicated by HE on lactulose and rifaximin to those on lactulose, rifaximin, and zinc. METHODS: This retrospective study included patients admitted with documented cirrhosis and home medications of lactulose and rifaximin, with or without zinc. Patients were stratified into 2 groups: those receiving lactulose and rifaximin for HE (control) and those receiving lactulose, rifaximin, and zinc for HE (treatment). The primary outcomes were 30-day and 1-year all-cause readmission rates. RESULTS: One-hundred fifty-seven patients were included (102 in control group, 55 in treatment group). Regarding 30-day and 1-year all-cause readmission rates, there was no difference between the control and treatment groups. CONCLUSION AND RELEVANCE: This is the first study conducted in the United States evaluating zinc for HE treatment. Zinc did not impact 30-day or 1-year all-cause readmission rates. Further studies are warranted to evaluate the potential benefit of zinc for HE, possibly in correlation with Model for End-stage Liver Disease-Sodium (MELD-Na) scores.

Lack of Access to Rifaximin Upon Hospital Discharge Is Frequent and Results in Increased Hospitalizations for Hepatic Encephalopathy.

BACKGROUND: Hepatic encephalopathy (HE) is a complication of cirrhosis. Rifaximin, added to lactulose, effectively maintains remission and reduces hospitalizations from HE compared with lactulose alone. Although the clinical evidence supports the use of rifaximin, concerns remain regarding the financial implications and subsequent impact on medication access and outcomes. OBJECTIVE: The goal of this study was to determine whether medication access to rifaximin at hospital discharge reduces readmission and office visits related to HE. METHODS: A retrospective study was conducted in compliance with local institutional review board including cirrhotic patients discharged with a rifaximin prescription for HE. Patients were stratified into 2 groups: those able to obtain rifaximin and those unable to obtain rifaximin upon discharge. The primary outcome was to evaluate the rate of HE recurrence in each group as defined as a composite of readmission or office visit for acute HE within 12 months of discharge. RESULTS: Access to rifaximin significantly reduced the risk of hospital admission and office visit for acute HE over 12 months. A hospitalization or office visit occurred in 24.5% of patients in the medication access group compared with 50% in the group without medication access. Only 58% of patients had access to rifaximin at discharge. CONCLUSION AND RELEVANCE: Rifaximin use was associated with significantly reduced risk of hospitalization and office visits for HE. At discharge, 42% of patients did not have access to rifaximin regardless of being prescribed the medication, identifying that copay is a significant barrier in allowing patients to have access to rifaximin.

A PK/PD model for the evaluation of clinical rifaximin dosage for the treatment of dairy cow mastitis induced by Escherichia coli.

Escherichia coli (E. coli) is an opportunistic pathogen that can cause clinical mastitis in dairy cows worldwide. Mastitis produces severe symptoms in dairy cows, such as udder inflammation, the production of harmful substances, reduced milk production, and altered milk quality. Intramammary injections of rifaximin have a beneficial effect on dairy cow mastitis, especially for mastitis caused by E. coli. However, we do not know whether the currently accepted clinical administration scheme is reasonable. Therefore, the purpose of this experiment was to evaluate the clinical dosing regimen for curing mastitis induced by E. coli. In this study, the pharmacokinetics of four single dose groups (50, 100, 200, and 400 µg/gland) were studied in CD-1 lactating mice, and the main pharmacokinetic parameters were obtained by non-compartment and two-compartment model of Phoenix 8.1 software. A total of 5,000 colony-forming units (CFU) of E. coli ATCC25922 were injected into the mammary glands of mice under anatomic microscope guidance. After 12 h of growth in vivo, the mouse mastitis model was successfully developed. In pharmacodynamics experiment, 12 different dosing regimens (doses ranged from 25 to 800 µg/gland and two dosing intervals of 12 and 24 h) were used to study the therapeutic potential of rifaximin for mastitis. The PK/PD model was established by integrating pharmacokinetics and pharmacodynamics using the inhibitory sigmoid Emax model. The optimal antibacterial effect was 2log10CFU/gland reduction of bacterial colony counts in vivo, when the magnitude of AUC24/MIC exceeded 57.80 h. A total of 57.80 h of AUC24/MIC was defined as a target value in the Monte Carlo simulation. The clinically recommended dosage regimen of 100 mg/gland every 12 h in a day achieved a 91.08% cure rate for the treatment of bovine mastitis caused by E. coli infection.