Rifaximin is safe and well tolerated for long-term maintenance of remission from overt hepatic encephalopathy

Hepatic Encephalopathy: An Update on the Pathophysiology and Therapeutic Options

Hepatic encephalopathy is a spectrum of reversible neuropsychiatric abnormalities, seen in patients with liver dysfunction and/or portosystemic shunting. One of the most debilitating complications of cirrhosis, encephalopathy affects 30-45% of cirrhotics. In addition to significantly affecting the lives of patients and their caregivers, it is also associated with increased morbidity and mortality as well as significant utilization of health care resources. In this paper, we provide an overview on the pathophysiology, diagnosis, management and newer therapies of hepatic encephalopathy.

The Effects of Probiotics and Symbiotics on Risk Factors for Hepatic Encephalopathy: A Systematic Review

Alterations in the levels of intestinal microbiota, endotoxemia, and inflammation are novel areas of interest in the pathogenesis of hepatic encephalopathy (HE). Probiotics and symbiotics are a promising treatment option for HE due to possible beneficial effects in modulating gut microflora and might be better tolerated and more cost-effective than the traditional treatment with lactulose, rifaximin or L-ornithine-L-aspartate. A systematic search of the electronic databases PubMed, ISI Web of Science, EMBASE, and Cochrane Library was conducted for randomized controlled clinical trials in adult patients with cirrhosis, evaluating the effect of probiotics and symbiotics in changes on intestinal microflora, reduction of endotoxemia, inflammation, and ammonia, reversal of minimal hepatic encephalopathy (MHE), prevention of overt hepatic encephalopathy (OHE), and improvement of quality of life. Nineteen trials met the inclusion criteria. Probiotics and symbiotics increased beneficial microflora and decreased pathogenic bacteria and endotoxemia compared with placebo/no treatment, but no effect was observed on inflammation. Probiotics significantly reversed MHE [risk ratio, 1.53; 95% confidence interval (CI): 1.14, 2.05; P=0.005] and reduced OHE development (risk ratio, 0.62; 95% CI: 0.48, 0.80; P=0.0002) compared with placebo/no treatment. Symbiotics significantly decreased ammonia levels compared with placebo (15.24; 95% CI: -26.01, -4.47; P=0.006). Probiotics did not show any additional benefit on reversal of MHE and prevention of OHE development when compared with lactulose, rifaximin, and L-ornithine-L-aspartate. Only 5 trials considered tolerance with minimal side effects reported. Although further research is warranted, probiotics and symbiotics should be considered as an alternative therapy for the treatment and management of HE given the results reported in this systematic review.

Guidelines for the prevention and treatment of travelers' diarrhea: a graded expert panel report

BACKGROUND

: Travelers' diarrhea causes significant morbidity including some sequelae, lost travel time and opportunity cost to both travelers and countries receiving travelers. Effective prevention and treatment are needed to reduce these negative impacts.

METHODS

: This critical appraisal of the literature and expert consensus guideline development effort asked several key questions related to antibiotic and non-antibiotic prophylaxis and treatment, utility of available diagnostics, impact of multi-drug resistant (MDR) colonization associated with travel and travelers' diarrhea, and how our understanding of the gastrointestinal microbiome should influence current practice and future research. Studies related to these key clinical areas were assessed for relevance and quality. Based on this critical appraisal, guidelines were developed and voted on using current standards for clinical guideline development methodology.

RESULTS

: New definitions for severity of travelers' diarrhea were developed. A total of 20 graded recommendations on the topics of prophylaxis, diagnosis, therapy and follow-up were developed. In addition, three non-graded consensus-based statements were adopted.

CONCLUSIONS

: Prevention and treatment of travelers' diarrhea requires action at the provider, traveler and research community levels. Strong evidence supports the effectiveness of antimicrobial therapy in most cases of moderate to severe travelers' diarrhea, while either increasing intake of fluids only or loperamide or bismuth subsalicylate may suffice for most cases of mild diarrhea. Further studies are needed to address knowledge gaps regarding optimal therapies, the individual, community and global health risks of MDR acquisition, manipulation of the microbiome in prevention and treatment and the utility of laboratory testing in returning travelers with persistent diarrhea.

Rifaximin has no effect on hemodynamics in decompensated cirrhosis: A randomized, double-blind, placebo-controlled trial

Decompensated cirrhosis is characterized by disturbed systemic and splanchnic hemodynamics. Bacterial translocation from the gut is considered the key driver in this process. Intestinal decontamination with rifaximin may improve hemodynamics. This double-blind, randomized, controlled trial (clinicaltrials.gov, NCT01769040) investigates the effects of rifaximin on hemodynamics, renal function, and vasoactive hormones. We randomized 54 stable outpatients with cirrhosis and ascites to rifaximin 550 mg twice a day (n = 36) or placebo twice a day (n = 18). Forty-five patients were male, mean age 56 years (±8.4), average Child score 8.3 (±1.3), and Model for End-Stage Liver Disease score 11.7 (±3.9). Measurements of hepatic venous pressure gradient, cardiac output, and systemic vascular resistance were made at baseline and after 4 weeks. The glomerular filtration rate and plasma renin, noradrenaline, lipopolysaccharide binding protein, troponin T, and brain natriuretic peptide levels were measured. Rifaximin had no effect on hepatic venous pressure gradient, mean 16.8 ± 3.8 mm Hg at baseline versus 16.6 ± 5.3 mm Hg at follow-up, compared to the placebo, mean 16.4 ± 4 mm Hg at baseline versus 16.3 ± 4.4 mm Hg at follow-up, P = 0.94. No effect was found on cardiac output, mean 6.9 ± 1.7 L/min at baseline versus 6.9 ± 2.3 L/min at follow-up, compared to placebo, mean 6.6 ± 1.9 L/min at baseline compared to 6.5 ±2.1 L/min at follow-up, P = 0.66. No effects on the glomerular filtration rate, P = 0.14, or vasoactive hormones were found. Subgroup analyses on patients with increased lipopolysaccharide binding protein and systemic vascular resistance below the mean (1,011 dynes × s/cm⁵ ) revealed no effect of rifaximin.

CONCLUSION

Four weeks of treatment with rifaximin did not reduce the hepatic venous pressure gradient or improve systemic hemodynamics in patients with cirrhosis and ascites; rifaximin did not affect glomerular filtration rate or levels of vasoactive hormones. (Hepatology 2017;65:592-603).

Therapeutic Modulation of Gut Microbiota in Functional Bowel Disorders

Functional bowel disorders (FBDs) are functional gastrointestinal disorders with symptoms attributable to the middle or lower gastrointestinal tract. These include irritable bowel syndrome, functional bloating, functional constipation, functional diarrhea, and unspecified FBD. Increasing evidence has emerged of late that intestinal microbiota is involved in the pathogenesis of FBDs. In this review, the therapeutic benefits and future perspectives of the currently available strategies for modifying the gut microbiota in FBDs are described, focusing primarily on irritable bowel syndrome and functional constipation.

Repeat Rifaximin for Irritable Bowel Syndrome: No Clinically Significant Changes in Stool Microbial Antibiotic Sensitivity

BACKGROUND

Rifaximin has demonstrated efficacy and safety for diarrhea-predominant irritable bowel syndrome (IBS-D).

AIM

To determine the rifaximin repeat treatment effect on fecal bacterial antibiotic susceptibility.

METHODS

Patients with IBS in Trial 3 (TARGET 3) study who responded to open-label rifaximin 550 mg three times daily for 2 weeks, with symptom recurrence within 18 weeks, were randomized to double-blind treatment: two 2-week repeat courses of rifaximin or placebo, separated by 10 weeks. Prospective stool sample collection occurred before and after open-label rifaximin, before and after the first repeat course, and at the end of the study. Susceptibility testing was performed with 11 antibiotics, including rifaximin and rifampin, using broth microdilution or agar dilution methods.

RESULTS

Of 103 patients receiving open-label rifaximin, 73 received double-blind rifaximin (n = 37) or placebo (n = 36). A total of 1429 bacterial and yeast isolates were identified, of which Bacteroidaceae (36.7%) and Enterobacteriaceae (33.9%) were the most common. In the double-blind phase, Clostridium difficile was highly susceptible to rifaximin [minimum inhibitory concentration (MIC) range 0.008-1 µg/mL] and rifampin (MIC range 0.004-0.25 µg/mL). Following double-blind rifaximin treatment, Staphylococcus isolates remained susceptible to rifaximin at all visits (MIC₅₀ range ≤0.06-32 µg/mL). Rifaximin exposure was not associated with long-term cross-resistance of Bacteroidaceae, Enterobacteriaceae, and Enterococcaceae to rifampin or nonrifamycin antibiotics tested.

CONCLUSIONS

In this study, short-term repeat treatment with rifaximin has no apparent long-term effect on stool microbial susceptibility to rifaximin, rifampin, and nonrifamycin antibiotics. CLINICALTRIALS.

GOV IDENTIFIER

NCT01543178.

Gut microbiome and liver disease

Gut microbiota changes are important in determining the occurrence and progression of chronic liver disease related to alcohol, nonalcoholic fatty liver disease, and cirrhosis. Specifically, the systemic inflammation, endotoxemia, and the vasodilation that leads to complications such as spontaneous bacterial peritonitis and hepatic encephalopathy could be related to the gut milieu. Given the poor prognosis of these events, their prevention and early management are essential. Microbiota may be an essential component of the gut milieu that can impact these clinical events, and the study of their composition and function in a culture-independent manner could help understand the prognosis. Recent human and animal studies have shown that the relative abundance and the functional changes of microbiota in the stool, colonic mucosa, and saliva have varying consequences on the presence and prognosis of chronic liver disease and cirrhosis. The impact of therapies on the microbiota is slowly being understood and will likely lead to a more targeted approach to gut microbiota modification in chronic liver disease and cirrhosis.

Rifaximin for the treatment of diarrhea-predominant irritable bowel syndrome

Irritable bowel syndrome (IBS) is a chronic, functional bowel disorder characterized by abdominal pain or discomfort and altered bowel habit. The pathophysiology is unclear, but may include altered gut motility, visceral hypersensitivity, abnormal central pain processing, chronic low-grade intestinal inflammation, or disturbances in the gut microbiome. These etiological mechanisms, alongside environmental factors such as stress and anxiety, vary between individuals and represent potential targets for treatment. Rifaximin is a poorly absorbed oral antibiotic proposed to act on the gut microenvironment, used in the treatment of travelers' diarrhea and hepatic encephalopathy. Clinical trials suggest the drug can reduce global IBS symptoms and improve bloating, abdominal pain, and stool consistency in some patients with non-constipated IBS, leading to Food and Drug Administration approval in the United States. This article considers the pharmacology of rifaximin, the evidence for its use in IBS, and the safety and tolerability of the drug.

Rifaximin Decreases the Incidence and Severity of Acute Kidney Injury and Hepatorenal Syndrome in Cirrhosis

BACKGROUND

While the effects of rifaximin have been shown to be protective against acute kidney injury (AKI) and hepatorenal syndrome (HRS) in alcohol-induced cirrhosis, its long-term effects on the renal function of other cirrhotic patients are unknown.

AIM

To examine the long-term effects of rifaximin on the renal function of patients with cirrhosis from various etiologies.

METHODS

In a retrospective study, we examined cirrhotic patients at the University of Chicago Liver Clinic from January 1, 2011, to December 31, 2014. The study enrolled patients on rifaximin for ≥90 days, who were then matched by age, gender, and MELD score to a control group. Patients with malignancy and renal replacement therapy (RRT) at baseline were excluded. Data were censored at the last follow-up, termination of rifaximin therapy, initiation of RRT, death, or liver transplant.

RESULTS

Eighty-eight rifaximin cases were identified and matched to 88 control cases. Baseline characteristics were similar, with the exceptions of more prevalent long-term midodrine use (≥90 days) (17.0 vs 4.5 %, p = 0.01) and baseline ascites (37.5 vs 23.8 %, p = 0.05) in the rifaximin group. There was no difference in the frequency of infections, deaths, liver transplants, or hospitalizations. After controlling for cofounders, the incidence rate ratio of AKI (IRR 0.71, p = 0.02) and HRS (IRR 0.21, p = 0.02), as well as the risk of requiring RRT (OR 0.23, p = 0.01), was lower in the rifaximin group.

CONCLUSIONS

Long-term use of rifaximin is associated with a decrease incidence of AKI and HRS and a decrease risk of requiring RRT in a general population of cirrhotic patients.

Antibiotics as deep modulators of gut microbiota: between good and evil

The recent increase in our knowledge of human gut microbiota has changed our view on antibiotics. Antibiotics are, indeed, no longer considered only beneficial, but also potentially harmful drugs, as their abuse appears to play a role in the pathogenesis of several disorders associated with microbiota impairment (eg, Clostridium difficile infection or metabolic disorders). Both drug-related factors (such as antibiotic class, timing of exposure or route of administration) and host-related factors appear to influence the alterations of human gut microbiota produced by antibiotics. Nevertheless, antibiotics are nowadays considered a reliable therapy for some non-communicable disorders, including IBS or hepatic encephalopathy. Moreover, some antibiotics can also act positively on gut microbiota, providing a so-called 'eubiotic' effect, by increasing abundance of beneficial bacteria. Therefore, antibiotics appear to change, for better or worse, the nature of several disorders, including IBS, IBD, metabolic disorders or liver disease. This reviews aims to address the potential of antibiotics in the development of major non-communicable disorders associated with the alteration of gut microbiota and on newly discovered therapeutic avenues of antibiotics beyond the cure of infectious diseases.

Use of rifaximin in gastrointestinal and liver diseases

Rifaximin is a broad spectrum oral antibiotic with antimicrobial activity against Gram-positive and Gram-negative aerobic and anaerobic bacteria. It is poorly absorbed and thus has a highly favorable safety profile. Rifaximin has been shown to be effective in the treatment of traveler’s diarrhea, functional bloating and irritable bowel syndrome, small bowel bacterial overgrowth and in the prevention of recurrent overt hepatic encephalopathy. In addition, there is emerging evidence for a possible beneficial effect of rifaximin in the treatment of uncomplicated diverticular disease and in the prevention of recurrent diverticulitis. The use of rifaximin is associated with a low incidence of development, or persistence of spontaneous bacterial mutants. Moreover, the development of important drug resistance among extra-intestinal flora during rifaximin therapy is unlikely because of minimal systemic absorption and limited cross-resistance of rifaximin with other antimicrobials. This review addresses the current and emerging role of rifaximin in the treatment of gastrointestinal and liver disorders.

Probiotics are helpful in hepatic encephalopathy: a meta-analysis of randomized trials

BACKGROUND

Hepatic encephalopathy (HE) is a major complication of cirrhosis and is associated with decreased survival and increased health care utilization.

AIM

The aim of this study was to evaluate the efficacy of probiotics in the management minimal hepatic encephalopathy HE (MHE) and overt HE (OHE) in comparison to no treatment/placebo and lactulose.

METHODS

The main outcomes measured were mortality, improvement in MHE, progression to OHE in patients with MHE and hospitalization. We calculated odds ratios (OR) with 95% confidence intervals (CI). Study heterogeneity was assessed using the I(2) statistic.

RESULTS

Fourteen studies totalling 1152 patients were included in the analysis. The use of probiotics had no impact on the overall mortality when compared to either lactulose (OR: 1.07, 95% CI: 0.47-2.44, P = 0.88) or no treatment/placebo (OR: 0.69, 95% CI: 0.42-1.14, P = 0.15). When probiotics was compared to no treatment/placebo, it was associated with a significant improvement in MHE (OR: 3.91, 95% CI: 2.25-6.80, P < 0.00001), decreased hospitalization rates (OR: 0.53, 95% CI: 0.33-0.86, P = 0.01) and decreased progression to overt hepatic encephalopathy (OR: 0.40, 95% CI: 0.26-0.60, P < 0.0001). However when compared to lactulose, probiotics did not show a significant difference in improvement of MHE (OR: 0.81, 95% CI: 0.52-1.27, P = 0.35), hospitalization rates (OR: 1.02, 95% CI: 0.52-1.99, P = 0.96) or progression to overt hepatic encephalopathy (OR: 1.24, 95% CI 0.73-2.10, P = 0.42).

CONCLUSIONS

Overall the use of probiotics was more effective in decreasing hospitalization rates, improving MHE and preventing progression to OHE in patients with underlying MHE than placebo, but similar to that seen with lactulose. The use of probiotics did not affect mortality rates.

Rifamycins, Alone and in Combination

Rifamycins inhibit RNA polymerase of most bacterial genera. Rifampicin remains part of combination therapy for treating tuberculosis (TB), and for treating Gram-positive prosthetic joint and valve infections, in which biofilms are prominent. Rifabutin has use for AIDS patients in treating mycobacterial infections TB and Mycobacterium avium complex (MAC), having fewer drug-drug interactions that interfere with AIDS medications. Rifabutin is occasionally used in combination to eradicate Helicobacter pylori (peptic ulcer disease). Rifapentine has yet to fulfill its potential in reducing time of treatment for TB. Rifaximin is a monotherapeutic agent to treat gastrointestinal (GI) disorders, such as hepatic encephalopathy, irritable bowel syndrome, and travelers' diarrhea. Rifaximin is confined to the GI tract because it is not systemically absorbed on oral dosing, achieving high local concentrations, and showing anti-inflammatory properties in addition to its antibacterial activity. Resistance issues are unavoidable with all the rifamycins when the bioburden is high, because of mutations that modify RNA polymerase.

Quantification of Rifaximin in Tablets by Spectrophotometric Method Ecofriendly in Ultraviolet Region

Rifaximin is an oral nonabsorbable antibiotic that acts locally in the gastrointestinal tract with minimal systemic adverse effects. It does not have spectrophotometric method ecofriendly in the ultraviolet region described in official compendiums and literature. The analytical techniques for determination of rifaximin reported in the literature require large amount of time to release results and are significantly onerous. Furthermore, they use toxic reagents both for the operator and environment and, therefore, cannot be considered environmentally friendly analytical techniques. The objective of this study was to develop and validate an ecofriendly spectrophotometric method in the ultraviolet region to quantify rifaximin in tablets. The method was validated, showing linearity, selectivity, precision, accuracy, and robustness. It was linear over the concentration range of 10-30 mg L(-1) with correlation coefficients greater than 0.9999 and limits of detection and quantification of 1.39 and 4.22 mg L(-1), respectively. The validated method is useful and applied for the routine quality control of rifaximin, since it is simple with inexpensive conditions and fast in the release of results, optimizes analysts and equipment, and uses environmentally friendly solvents, being considered a green method, which does not prejudice either the operator or the environment.

Rifaximin, a non-absorbable antibiotic, inhibits the release of pro-angiogenic mediators in colon cancer cells through a pregnane X receptor-dependent pathway

Activation of intestinal human pregnane X receptor (PXR) has recently been proposed as a promising strategy for the chemoprevention of inflammation-induced colon cancer. The present study was aimed at evaluating the effect of rifaximin, a non-absorbable antibiotic, in inhibiting angiogenesis in a model of human colorectal epithelium and investigating the role of PXR in its mechanism of action. Caco-2 cells were treated with rifaximin (0.1, 1.0 and 10.0 µM) in the presence or absence of ketoconazole (10 µM) and assessed for cell proliferation, migration and expression of proliferating cell nuclear antigen (PCNA). The release of vascular endothelial growth factor (VEGF) and nitric oxide (NO), expression of Akt, mechanistic target of rapamycin (mTOR), p38 mitogen activated protein kinases (MAPK), nuclear factor κB (NF-κB) and metalloproteinase-2 and -9 (MMP-2 and -9) were also evaluated. Treatment with rifaximin 0.1, 1.0 and 10.0 µM caused significant and concentration-dependent reduction of cell proliferation, cell migration and PCNA expression in the Caco-2 cells vs. untreated cells. Treatment downregulated VEGF secretion, NO release, VEGFR-2 expression, MMP-2 and MMP-9 expression vs. untreated cells. Rifaximin treatment also resulted in a concentration-dependent decrease in the phosphorylation of Akt, mTOR, p38MAPK and inhibition of hypoxia-inducible factor 1-α (HIF-1α), p70S6K and NF-κB. Ketoconazole (PXR antagonist) treatment inhibited these effects. These findings demonstrated that rifaximin causes PXR-mediated inhibition of angiogenic factors in Caco-2 cell line and may be a promising anticancer tool.

Rifaximin for the treatment of irritable bowel syndrome - a drug safety evaluation

INTRODUCTION

Irritable bowel syndrome is a functional gastrointestinal disorder with a multifactorial etiology. Alterations of intestinal motility and immunity, gut-brain interactions, as well as gut microbiota dysbiosis contribute to the development of irritable bowel syndrome. Therefore, gut microbiota modulation by non-absorbable antibiotics is a therapeutic option in patients with IBS.

AREAS COVERED

Published articles including patients with irritable bowel syndrome reporting data about rifaximin activity and safety have been searched throughout the literature and selected.

EXPERT OPINION

The optimal antibiotic molecule should be local-acting, long-acting and safe-acting. Rifaximin is a non-absorbable antibiotic with additional anti-inflammatory and gut microbiota-modulating activity. It is effective in inducing symptoms relief in patients with IBS, even after repeated treatment courses. Rifaximin-related side effects in patients with IBS are reported to be mild and infrequent; microbial resistance is rare and transient, due to the high local concentration of the drug and to the absence of horizontal transmission. Clostridium difficile infection is not usual in patients receiving rifaximin in absence of predisposing conditions such as hospitalization and immunosuppression, which are uncommon in patients affected by irritable bowel syndrome. Nevertheless rifaximin is an antibiotic active against Clostridium difficile infection. Rifaximin has limited metabolic interactions and is not expected to interfere with drug metabolism in patients with normal hepatic function. These properties make rifaximin a safe antibiotic for gut microbiota modulation in patients with IBS.

Novel prevention strategies for bacterial infections in cirrhosis

INTRODUCTION

Bacterial infections are a serious complication of cirrhosis, as they can lead to decompensation, multiple organ failure, and/or death. Preventing infections is therefore very relevant. Because gut bacterial translocation is their main pathogenic mechanism, prevention of infections is mostly based on the use of orally administered poorly absorbed antibiotics such as norfloxacin (selective intestinal decontamination). However, antibiotic prophylaxis leads to antibiotic resistance, limiting therapy and increasing morbidity and mortality. Prevention of bacterial infections in cirrhosis should therefore move away from antibiotics.

AREAS COVERED

This review focuses on various potentially novel methods to prevent infections in cirrhosis focusing on non-antibiotic strategies. The use of probiotics, nonselective intestinal decontamination with rifaximin, prokinetics and beta-blockers or fecal microbiota transplant as means of targeting altered gut microbiota, bile acids and FXR agonists are all potential alternatives to selective intestinal decontamination. Prokinetics and beta-blockers can improve intestinal motility, while bile acids and FXR agonists help by improving the intestinal barrier. Finally, granulocyte colony stimulating factor (G-CSF) and statins are emerging therapeutic strategies that may improve immune dysfunction in cirrhosis.

EXPERT OPINION

Evidence for these strategies has been restricted to animal studies and proof-of concept studies but we expect this to change in coming years.

Review article: potential mechanisms of action of rifaximin in the management of hepatic encephalopathy and other complications of cirrhosis

BACKGROUND

Progressive gut milieu (microbiota) changes occur in patients with cirrhosis and are associated with complications [e.g. hepatic encephalopathy (HE)].

AIM

To examine the role of rifaximin in the management of HE and other complications of cirrhosis, including potential mechanisms of action and the need for future studies.

METHODS

A literature search was conducted using the keywords 'rifaximin', 'hepatic encephalopathy', 'ascites', 'variceal bleeding', 'peritonitis', 'portal hypertension', 'portopulmonary hypertension' and 'hepatorenal syndrome'.

RESULTS

The nonsystemic agent rifaximin reduces the risk of HE recurrence and HE-related hospitalisations in cirrhosis. In patients with cirrhosis, rifaximin modulates the bacterial composition of the gut microbiota without a consistent effect on overall faecal microbiota composition. However, rifaximin can impact the function or activities of the gut microbiota. For example, rifaximin significantly increased serum levels of long-chain fatty acids and carbohydrate metabolism intermediates in patients with minimal HE. Rifaximin also favourably affects serum proinflammatory cytokine and faecal secondary bile acid levels.

CONCLUSIONS

The gut microenvironment and associated microbiota play an important role in the pathogenesis of HE and other cirrhosis-related complications. Rifaximin's clinical activity may be attributed to effects on metabolic function of the gut microbiota, rather than a change in the relative bacterial abundance.

Effect of rifaximin on gut microbiota composition in advanced liver disease and its complications

Liver cirrhosis is a paradigm of intestinal dysbiosis. The qualitative and quantitative derangement of intestinal microbial community reported in cirrhotic patients seems to be strictly related with the impairment of liver function. A kind of gut microbial “fingerprint”, characterized by the reduced ratio of “good” to “potentially pathogenic” bacteria has recently been outlined, and is associated with the increase in Model for End-Stage Liver Disease and Child Pugh scores. Moreover, in patients presenting with cirrhosis complications such as spontaneous bacterial peritonitis (SBP), hepatic encephalopathy (HE), and, portal hypertension intestinal microbiota modifications or the isolation of bacteria deriving from the gut are commonly reported. Rifaximin is a non-absorbable antibiotic used in the management of several gastrointestinal diseases. Beyond bactericidal/bacteriostatic, immune-modulating and anti-inflammatory activity, a little is known about its interaction with gut microbial environment. Rifaximin has been demonstrated to exert beneficial effects on cognitive function in patients with HE, and also to prevent the development of SBP, to reduce endotoxemia and to improve hemodynamics in cirrhotics. These results are linked to a shift in gut microbes functionality, triggering the production of favorable metabolites. The low incidence of drug-related adverse events due to the small amount of circulating drug makes rifaximin a relatively safe antibiotic for the modulation of gut microbiota in advanced liver disease.

[Role of rifaximin in the treatment of hepatic encephalopathy]

Hepatic encephalopathy (HE) is a frequent and serious complication of liver cirrhosis. In addition to correction of the precipitating factors, the most commonly used treatments are non-absorbable disaccharides and rifaximin. Many of the recommendations are based on current clinical practice and there are few randomized controlled trials. Currently, rifaximin should be initiated during an episode of EH if, after 24-48 hours of non-absorbable disaccharide therapy, there is no clinical improvement. In recurrent EH, it is advisable to add rifaximin in patients under non-absorbable disaccharide therapy who develop a new episode. Currently, standard treatment with rifaximin for minimal EH is not recommended. Rifaximin is effective in the acute treatment of overt encephalopathy and in preventing recurrence.

Covert and Overt Hepatic Encephalopathy: Diagnosis and Management

Hepatic encephalopathy (HE) is part of a spectrum of neurocognitive changes in cirrhosis. HE is divided into 2 broad categories based on severity: covert hepatic encephalopathy (CHE) and overt hepatic encephalopathy (OHE). CHE has a significant impact on a patient's quality of life, driving performance, and recently has been associated with increased hospitalizations and death. Likewise, OHE is associated with increased rates of hospitalizations and mortality, and poor quality of life. Given its significant burden on patients, care takers, and the health care system, early diagnosis and management are imperative. In addition, focus also should be directed on patient and family member education on the disease progression and adherence to medications. Treatment strategies include the use of nonabsorbable disaccharides, antibiotics (ie, rifaximin), and, potentially, probiotics. Other therapies currently under further investigation include L-ornithine-L-aspartate, ornithine phenylacetate, glycerol phenylbutyrate, molecular adsorbent recirculating system, and albumin infusion.

Treatment of Overt Hepatic Encephalopathy

Hepatic encephalopathy (HE) is defined by an altered mental status in the setting of portosystemic shunting, with or without cirrhosis. The basis of HE is probably multi-factorial, but increased ammonia delivery to the brain is thought to play a pivotal role. Medical therapies have typically focused on reducing blood ammonia concentrations. These measures are moderately effective, but further improvements will require identification of new therapeutic targets. Two medications, lactulose and rifaximin, are currently approved for the treatment of HE in the USA - new compounds are available off-label, and are in clinical trials. The presence of HE is associated with a higher risk of death in cirrhotic patients. Liver transplantation typically cures HE, but HE does not increase the MELD score, and therefore does not contribute to the likelihood of liver transplantation.

Therapeutic Effects and Mechanisms of Action of Rifaximin in Gastrointestinal Diseases

Emerging preclinical and clinic evidence described herein suggests that the mechanism of action of rifaximin is not restricted to direct antibacterial effects within the gastrointestinal tract. Data from this study were derived from general and clinical trial-specific PubMed searches of English-language articles on rifaximin available through December 3, 2014. Search terms included rifaximin alone and in combination (using the Boolean operation "AND") with travelers' diarrhea, hepatic encephalopathy, liver cirrhosis, irritable bowel syndrome, inflammatory bowel disease, and Crohn's disease. Rifaximin appears to reduce bacterial virulence and pathogenicity by inhibiting bacterial translocation across the gastrointestinal epithelial lining. Rifaximin was shown to decrease bacterial adherence to epithelial cells and subsequent internalization in a bacteria- and cell type-specific manner, without an alteration in bacterial counts, but with a down-regulation in epithelial proinflammatory cytokine expression. Rifaximin also appears to modulate gut-immune signaling. In animal models of inflammatory bowel disease, rifaximin produced therapeutic effects by activating the pregnane X receptor and thereby reducing levels of the proinflammatory transcription factor nuclear factor κB. Therefore, for a given disease state, rifaximin may act through several mechanisms of action to exert its therapeutic effects. Clinically, rifaximin 600 mg/d significantly reduced symptoms of travelers' diarrhea (eg, time to last unformed stool vs placebo [32.0 hours vs 65.5 hours, respectively; P=.001]). For the prevention of hepatic encephalopathy recurrence, data indicate that treating 4 patients with rifaximin 1100 mg/d for 6 months would prevent 1 episode of hepatic encephalopathy. For diarrhea-predominant irritable bowel syndrome, a significantly greater percentage (40.7%) of patients treated with rifaximin 1650 mg/d for 2 weeks experienced adequate global irritable bowel syndrome symptom relief vs placebo (31.7%; P<.001). Rifaximin may be best described as a gut microenvironment modulator with cytoprotection properties, and further studies are needed to determine whether these putative mechanisms of action play a direct role in clinical outcomes.

Engineering the gut microbiota to treat hyperammonemia

Increasing evidence indicates that the gut microbiota can be altered to ameliorate or prevent disease states, and engineering the gut microbiota to therapeutically modulate host metabolism is an emerging goal of microbiome research. In the intestine, bacterial urease converts host-derived urea to ammonia and carbon dioxide, contributing to hyperammonemia-associated neurotoxicity and encephalopathy in patients with liver disease. Here, we engineered murine gut microbiota to reduce urease activity. Animals were depleted of their preexisting gut microbiota and then inoculated with altered Schaedler flora (ASF), a defined consortium of 8 bacteria with minimal urease gene content. This protocol resulted in establishment of a persistent new community that promoted a long-term reduction in fecal urease activity and ammonia production. Moreover, in a murine model of hepatic injury, ASF transplantation was associated with decreased morbidity and mortality. These results provide proof of concept that inoculation of a prepared host with a defined gut microbiota can lead to durable metabolic changes with therapeutic utility.

Presentation and complications associated with cirrhosis of the liver

OBJECTIVE

To provide an understanding of the detrimental impact of cirrhosis and its complications, strengths and weaknesses of current treatment options for the management of these complications, and new developments in this rapidly changing field.

RESEARCH DESIGN AND METHODS

Relevant publications were identified via PubMed and Cochrane databases, with additional references obtained by reviewing bibliographies from selected articles.

RESULTS

Cirrhosis, a progressive liver disease, is characterized by fibrosis caused by chronic liver injury. Liver fibrosis impairs hepatic function and causes structural changes that result in portal hypertension. Most patients with cirrhosis remain asymptomatic until they develop decompensated cirrhosis. At this stage, patients experience complications associated with portal hypertension (i.e., the abnormal increase in portal vein pressure), including ascites, spontaneous bacterial peritonitis (SBP), hepatic encephalopathy (HE), hepatorenal syndrome, portopulmonary hypertension, or variceal bleeding. In addition, intestinal microbial translocation in patients with cirrhosis might also cause SBP and HE. Because the survival rate for patients with cirrhosis substantially decreases once complications develop, the key goals in treating patients with cirrhosis include both managing the underlying liver disease and preventing and treating related complications. In patients with compensated cirrhosis, the management strategy is to prevent variceal bleeding and other complications that can lead to decompensated cirrhosis. Patients with decompensated cirrhosis are typically referred for liver transplantation, and the main focus of pre-transplant management is to eliminate the cause of cirrhosis (e.g., excess alcohol consumption, hepatitis virus) and prevent the recurrence of each decompensating complication.

CONCLUSIONS

Although substantial progress has been made to prevent the complications and mortality associated with cirrhosis, liver transplantation in combination with resolution of the etiology of cirrhosis remains the only curative option for most patients. Emerging therapies such as anti-fibrotic agents hold promise in potentially halting or reversing the progression of cirrhosis, even in patients with decompensated cirrhosis.

Progress in treatment of hepatic encephalopathy

Hepatic encephalopathy (HE) is a common complication of severe liver disease and a common cause of mortality. Clinical features range from clinically imperceptible symptoms in minimal HE which require neuropsychological testing to identify, to abnormal behavior, mental deterioration, and even coma or death. It is a reversible progressive neuropsychiatric disorder that is associated with a decrease in quality of life and an increase in rate of hospitalization and consequent costs because patients are at risk for recurrence. Unfortunately, the prevalence of HE continues to rise for several reasons. For one, patients with viral hepatitis are now developing cirrhosis. Additionally, we are currently in the midst of a global obesity epidemic, which fuels the metabolic syndrome and nonalcoholic fatty liver disease, and these patients are now presenting in larger numbers with complications of chronic liver disease such as HE. The high morbidity and mortality combined with the costs underline the importance to search the effective treatment for HE. This article reviews the progress in the treatment of HE.

Rifaximin for the treatment of diarrhoea-predominant irritable bowel syndrome

INTRODUCTION

Rifaximin is a non-absorbable, semisynthetic antibiotic that acts as an inhibitor of bacterial RNA synthesis, with a broad spectrum of antibacterial activity. Due to its poor absorption, rifaximin has an increased exposure to the intestine, thus it is suitable for the treatment of many gastrointestinal (GI) diseases. In irritable bowel syndrome (IBS) pathogenesis, gut microbiota impairment may play a major role. The possibility of modulating intestinal bacteria using antibiotics, in particular, rifaximin, has been demonstrated to improve IBS symptoms in non-constipation subtypes of IBS.

AREAS COVERED

We reviewed the use of rifaximin in diarrhoea-predominant IBS, focusing on its pharmacokinetic characteristics, its absorption in GI disease, its lack of interaction with other drugs and its new extended release formulation.

EXPERT OPINION

Rifaximin, with its low systemic absorption and no clinically significant interactions with other drugs, may represent a treatment of choice for IBS, mainly due to its ability to act on IBS pathogenesis, through the modulation of gut microbiota. Further studies to analyse the effect of rifaximin treatment on the composition of faecal microbiota are warranted. In particular, they need to evaluate whether resistant bacterial strains are selected and whether they are still present in the faecal sample even a long time after therapy.

Prolonged remission from hepatic encephalopathy with rifaximin: results of a placebo crossover analysis

BACKGROUND

Rifaximin therapy reduced risk of hepatic encephalopathy (HE) recurrence and HE-related hospitalisations during a 6-month, randomised, placebo-controlled trial (RCT) and a 24-month open-label maintenance (OLM) study. However, the impact of crossover from placebo to rifaximin therapy is unclear.

AIM

To study the impact of crossing over from placebo to rifaximin treatment on breakthrough HE and hospitalisation rates using a within-subjects design.

METHODS

Adults with cirrhosis and history of overt HE episodes, currently in HE remission, received placebo during the RCT and crossed over to rifaximin 550 mg twice daily during the OLM study. Rate of breakthrough overt HE episodes, hospitalisations and incidence and rate of adverse events (AEs) were analysed during RCT and first 6 months of OLM.

RESULTS

Of 82 patients randomised to placebo in the RCT who crossed over to the OLM study, 39 experienced an HE episode during the RCT compared with 14 during the OLM study (P < 0.0001). Significantly lower rates of HE events were observed with rifaximin treatment compared with placebo treatment (P < 0.0001). Rates of HE-related hospitalisation were numerically lower during rifaximin treatment compared with placebo treatment, although not significant. Rates of most common AEs, serious AEs and infection-related AEs were similar between the two treatments.

CONCLUSIONS

This analysis confirms the repeatability of results from the RCT on safety and efficacy of rifaximin 550 mg twice daily in reducing the risk of hepatic encephalopathy recurrence, and suggests these findings are translatable outside of a rigorous, controlled trial setting.

Activation of intestinal human pregnane X receptor protects against azoxymethane/dextran sulfate sodium-induced colon cancer

The role of intestinal human pregnane X receptor (PXR) in colon cancer was determined through investigation of the chemopreventive role of rifaximin, a specific agonist of intestinal human PXR, toward azoxymethane (AOM)/dextran sulfate sodium (DSS)-induced colon cancer. Rifaximin treatment significantly decreased the number of colon tumors induced by AOM/DSS treatment in PXR-humanized mice, but not wild-type or Pxr-null mice. Additionally, rifaximin treatment markedly increased the survival rate of PXR-humanized mice, but not wild-type or Pxr-null mice. These data indicated a human PXR-dependent therapeutic chemoprevention of rifaximin toward AOM/DSS-induced colon cancer. Nuclear factor κ-light-chain-enhancer of activated B cells-mediated inflammatory signaling was upregulated in AOM/DSS-treated mice, and inhibited by rifaximin in PXR-humanized mice. Cell proliferation and apoptosis were also modulated by rifaximin treatment in the AOM/DSS model. In vitro cell-based assays further revealed that rifaximin regulated cell apoptosis and cell cycle in a human PXR-dependent manner. These results suggested that specific activation of intestinal human PXR exhibited a chemopreventive role toward AOM/DSS-induced colon cancer by mediating anti-inflammation, antiproliferation, and proapoptotic events.

Management of hepatic encephalopathy

OPINION STATEMENT

Hepatic encephalopathy management varies depending on the acuity of liver failure. However, in patients with either acute or chronic liver failure five basic steps in management are critical: stabilization, addressing modifiable precipitating factors, lowering blood ammonia, managing elevated intracranial pressure (ICP) (if present), and managing complications of liver failure that can contribute to encephalopathy, particularly hyponatremia. Because liver failure patients are prone to a variety of other medical problems that can lead to encephalopathy (such as coagulopathy associated intracranial hemorrhage, electrolyte disarray, renal failure, hypotension, hypoglycemia, and infection), a thorough history, physical and neurologic examination is mandated in all encephalopathic liver failure patients. There should be a low threshold for brain imaging in patients with focal neurological deficits given the propensity for spontaneous intracranial hemorrhage. In patients with acute liver failure and high grade encephalopathy, identification of the etiology of acute liver failure is essential to guide treatment and antidote administration, particularly in the case of acetaminophen poisoning. Equally critical is management of elevated ICP in acute liver failure. Intracranial hypertension can be treated with hypertonic saline and/or adjustment of the dialysis bath. Placement of an intracranial monitor to guide ICP therapy is risky because of concomitant coagulopathy and remains controversial. Continuous renal replacement therapy may help lower serum ammonia, treat coexisting uremia, and improve symptoms. Liver transplantation is the definitive treatment for patients with acute liver failure and hepatic encephalopathy. In patients with chronic hepatic encephalopathy, lactulose and rifaxamin remain a mainstay of therapy. In these patients, it is essential to identify reversible causes of hepatic encephalopathy such as increased ammonia production and/or decreased clearance (eg, infection, GI bleed, constipation, hypokalemia, dehydration). Chronic hyponatremia should be managed by gradual sodium correction of no more than 8‒12 meq/L per day to avoid central myelinolysis syndrome. Free water restriction and increased dietary sodium are reasonable, cost effective treatment options. Many emerging therapies, both pharmacologic and interventional, are currently being studied to improve management of hepatic encephalopathy.

Treatment options for covert hepatic encephalopathy

OPINION STATEMENT

The main issue with treating covert hepatic encephalopathy (HE) is to establish whether it is cost effective to reverse the neuropsychiatric abnormalities that define this mild form of HE. Until fairly recently, covert HE was rarely diagnosed, but advances in computerized psychometric testing have greatly simplified its detection. The many consequences of covert HE are now being identified, and most have been shown to be reversible with standard HE treatment. Perhaps the most enticing possibility will be the potential that standard HE therapies will postpone the onset of overt HE. This will require further evaluation with large placebo-controlled randomized trials.