HelR is a helicase-like protein that protects RNA polymerase from rifamycin antibiotics.

Rifamycin antibiotics such as rifampin are potent inhibitors of prokaryotic RNA polymerase (RNAP) used to treat tuberculosis and other bacterial infections. Although resistance arises in the clinic principally through mutations in RNAP, many bacteria possess highly specific enzyme-mediated resistance mechanisms that modify and inactivate rifamycins. The expression of these enzymes is controlled by a 19-bp cis-acting rifamycin-associated element (RAE). Guided by the presence of RAE sequences, we identify a helicase-like protein, HelR, in Streptomyces venezuelae that confers broad-spectrum rifamycin resistance. We show that HelR also promotes tolerance to rifamycins, enabling bacterial evasion of the toxic properties of these antibiotics. HelR forms a complex with RNAP and rescues transcription inhibition by displacing rifamycins from RNAP, thereby providing resistance by target protection . Furthermore, HelRs are broadly distributed in Actinobacteria, including several opportunistic Mycobacterial pathogens, offering yet another challenge for developing new rifamycin antibiotics.

Mycobacterium abscessus HelR interacts with RNA polymerase to confer intrinsic rifamycin resistance.

Rifampicin (RIF), the frontline drug against M. tuberculosis, is completely ineffective against M. abscessus, partially due to the presence of an ADP-ribosyltransferase (Arr) that inactivates RIF. Using RNA-seq, we show that exposure of M. abscessus to sublethal doses of RIF and Rifabutin (RBT), a close analog of RIF, results in an ∼25-fold upregulation of Mab_helR in laboratory and clinical isolates. An isogenic deletion in Mab_helR results in RIF/RBT hypersensitivity, and overexpression of Mab_helR confers RIF tolerance in M. tuberculosis. We demonstrate an increased HelR-RNAP association in RIF-exposed bacteria and a MabHelR-mediated dissociation of RNAP from stalled initiation complexes in vitro. Finally, we show that the tip of the PCh-loop of Mab_helR, present in proximity to RIF, is critical for conferring RIF resistance but dispensable for dissociation of stalled RNAP complexes, suggesting that HelR-mediated RIF resistance requires a step in addition to displacement of RIF-stalled RNAP.

Mode of Action of Kanglemycin A, an Ansamycin Natural Product that Is Active against Rifampicin-Resistant Mycobacterium tuberculosis.

Antibiotic-resistant bacterial pathogens pose an urgent healthcare threat, prompting a demand for new medicines. We report the mode of action of the natural ansamycin antibiotic kanglemycin A (KglA). KglA binds bacterial RNA polymerase at the rifampicin-binding pocket but maintains potency against RNA polymerases containing rifampicin-resistant mutations. KglA has antibiotic activity against rifampicin-resistant Gram-positive bacteria and multidrug-resistant Mycobacterium tuberculosis (MDR-M. tuberculosis). The X-ray crystal structures of KglA with the Escherichia coli RNA polymerase holoenzyme and Thermus thermophilus RNA polymerase-promoter complex reveal an altered-compared with rifampicin-conformation of KglA within the rifampicin-binding pocket. Unique deoxysugar and succinate ansa bridge substituents make additional contacts with a separate, hydrophobic pocket of RNA polymerase and preclude the formation of initial dinucleotides, respectively. Previous ansa-chain modifications in the rifamycin series have proven unsuccessful. Thus, KglA represents a key starting point for the development of a new class of ansa-chain derivatized ansamycins to tackle rifampicin resistance.

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.

Diagnostic Performance of the ICD-10 Code K76.82 for Hepatic Encephalopathy in Patients With Cirrhosis.

INTRODUCTION: Hepatic encephalopathy (HE) is prevalent and is associated with increased morbidity and mortality among patients with cirrhosis. On October 1, 2022, a new, specific International Classification of Diseases-10 code for HE, K76.82, was introduced. We aimed to analyze the diagnostic accuracy of K76.82. METHODS: Diagnostic performance of K76.82 for HE (sensitivity, specificity, positive predictive ratio, and negative predictive ratio) was evaluated in 2 large health systems compared with lactulose, rifaximin, and K72.90. RESULTS: A total of 2,483 patients were analyzed. The combination term "lactulose or rifaximin" showed the highest sensitivity of >98% while K76.82 demonstrated a specificity of >87% in all cohorts. DISCUSSION: Although K76.82 is promising, the combination term "lactulose or rifaximin" identified patients with HE more accurately.

Efficacy of Rifaximin in Patients With Abdominal Bloating or Distension: A Systematic Review and Meta-analysis.

BACKGROUND: Abdominal bloating is a common complaint in patients with functional and organic bowel disease. Rifaximin, a nonabsorbable antibiotic, has been tried for the treatment of this disease. We performed a systematic review and meta-analysis to study the efficacy of rifaximin in abdominal bloating and distension in patients with functional gastrointestinal disorders (FGID). METHODS: We accessed 4 databases (MEDLINE, Embase, SCOPUS, and Web of Science) to identify randomized placebo-controlled trials that utilized rifaximin in FGID. We excluded observational studies, those including patients with organic bowel disorders such as inflammatory bowel diseases, or those in which rifaximin was given for other indications, such as hepatic encephalopathy. RESULTS: A total of 1426 articles were available, of which 813 articles were screened after removing duplicates and 34 articles were selected for full-text review. Finally, 10 trials (3326 patients) were included. Rifaximin was administered in doses ranging from 400 to 1650 mg per day for 1 to 2 weeks. Rifaximin therapy led to a higher likelihood of improvement in symptoms of bloating (44.6% vs. 34.6%, RR 1.22, 95% CI 1.11, 1.35; n=2401 patients) without significant heterogeneity. However, daily doses less than 1200 mg/day were similar to placebo ( P =0.09). Bloating was quantified subjectively in 7 studies, and rifaximin led to a greater reduction in bloating scores compared with placebo (standardized mean difference -0.3, 95% CI -0.51, -0.1, P =0.04) but carried significant heterogeneity ( I2 =61.6%, P =0.01). CONCLUSIONS: Rifaximin therapy is associated with an increased likelihood of improvement in bloating and distension, as well as reduces the subjective severity of these symptoms in patients with FGID.

Association between HIV and acquisition of rifamycin resistance with first-line TB treatment: a systematic review and meta-analysis.

BACKGROUND: Multi-drug or rifamycin-resistant tuberculosis (MDR/RR-TB) is an important public health concern, including in settings with high HIV prevalence. TB drug resistance can be directly transmitted or arise through resistance acquisition during first-line TB treatment. Limited evidence suggests that people living with HIV (PLHIV) might have an increased risk of acquired rifamycin-resistance (ARR). METHODS: To assess HIV as a risk factor for ARR during first-line TB treatment, a systematic review and meta-analysis was conducted. ARR was defined as rifamycin-susceptibility at treatment start with rifamycin-resistance diagnosed during or at the end of treatment, or at recurrence. PubMed/MEDLINE, CINAHL, Cochrane Library, and Google Scholar databases were searched from inception to 23 May 2024 for articles in English; conference abstracts were also searched from 2004 to 2021. The Mantel-Haenszel random-effects model was used to estimate the pooled odds ratio of any association between HIV and ARR among individuals receiving first-line TB treatment. RESULTS: Ten studies that included data collected between 1990 and 2014 were identified: five from the United States, two from South Africa and one each from Uganda, India and Moldova. A total of 97,564 individuals were included across all studies, with 13,359 (13.7%) PLHIV. Overall, 312 (0.32%) acquired rifamycin-resistance, among whom 115 (36.9%) were PLHIV. The weighted odds of ARR were 4.57 (95% CI, 2.01-10.42) times higher among PLHIV compared to HIV-negative individuals receiving first-line TB treatment. CONCLUSION: The available data, suggest that PLHIV have an increased ARR risk during first-line TB treatment. Further research is needed to clarify specific risk factors, including advanced HIV disease and TB disease severity. Given the introduction of shorter, 4-month rifamycin-based regimens, there is an urgent need for additional data on ARR, particularly for PLHIV. SYSTEMATIC REVIEW REGISTRATION: PROSPERO CRD42022327337.

Amycolatopsis mediterranei: A Sixty-Year Journey from Strain Isolation to Unlocking Its Potential of Rifamycin Analogue Production by Combinatorial Biosynthesis.

Ever since the isolation of Amycolatopsis mediterranei in 1957, this strain has been the focus of research worldwide. In the last 60 years or more, our understanding of the taxonomy, development of cloning vectors and conjugation system, physiology, genetics, genomics, and biosynthetic pathway of rifamycin B production in A. mediterranei has substantially increased. In particular, the development of cloning vectors, transformation system, characterization of the rifamycin biosynthetic gene cluster, and the regulation of rifamycin B production by the pioneering work of Heinz Floss have made the rifamycin polyketide biosynthetic gene cluster (PKS) an attractive target for extensive genetic manipulations to produce rifamycin B analogues which could be effective against multi-drug-resistant tuberculosis. Additionally, a better understanding of the regulation of rifamycin B production and the application of newer genomics tools, including CRISPR-assisted genome editing systems, might prove useful to overcome the limitations associated with low production of rifamycin analogues.

Genome-Driven Discovery of Hygrocins in Streptomyces rapamycinicus.

Ansamycins, represented by the antituberculosis drug rifamycin, are an important family of natural products. To obtain new ansamycins, Streptomyces rapamycinicus IMET 43975 harboring an ansamycin biosynthetic gene cluster was fermented in a 50 L scale, and subsequent purification work led to the isolation of five known and four new analogues, where hygrocin W (2) belongs to benzoquinonoid ansamycins, and the other three hygrocins, hygrocins X-Z (6-8), are new seco-hygrocins. The structures of ansamycins (1-8) were determined by the analysis of spectroscopic (1D/2D NMR and ECD) and MS spectrometric data. The Baeyer-Villiger enzyme which catalyzed the ester formation in the ansa-ring was confirmed through in vivo CRISPR base editing. The discovery of these compounds further enriches the structural diversity of ansamycins.

Novel antibody-antibiotic conjugate using KRM-1657 as payload eliminates intracellular MRSA in vitro and in vivo.

Staphylococcus aureus is considered to be an extracellular pathogen. However, survival of S.aureus within host cells may cause long-term colonization and clinical failure. Current treatments have poor efficacy in clearing intracellular bacteria. Antibody-antibiotic conjugates (AACs) is a novel strategy for eliminating intracellular bacteria. Herein, we use KRM-1657 as payload of AAC for the first time, and we conjugate it with anti S. aureus antibody via a dipeptide linker (Valine-Alanine) to obtain a novel AAC (ASAK-22). The ASAK-22 exhibits good in vitro pharmacokinetic properties and inhibitory activity against intracellular MRSA, with 100 µg/mL of ASAK-22 capable of eliminating intracellular MRSA to the detection limit. Furthermore, the in vivo results demonstrate that a single administration of ASAK-22 significantly reduces the bacterial burden in the bacteremia model, which is superior to the vancomycin treatment.

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.

Evaluation of Mycobacterium Avium Complex Pulmonary Disease Treatment Completion and Adherence to ATS/IDSA Guidelines.

BACKGROUND: Nontuberculous mycobacteria are environmental organisms that cause infections leading to chronic, debilitating pulmonary disease, among which Mycobacterium avium complex (MAC) is the most common species. METHODS: We described patterns of macrolide-based multidrug antibiotic therapies for MAC pulmonary disease (MAC-PD) in US Medicare beneficiaries with bronchiectasis between January 2006 and December 2014. MAC therapy was defined as a multidrug regimen containing a macrolide plus ≥1 other drug targeting MAC-PD (rifamycin, ethambutol, fluoroquinolone, or amikacin) prescribed concomitantly for >28 days. RESULTS: We identified 9189 new MAC therapy users, with a mean age (standard deviation) of 74 (6 years) at the start of therapy; 75% female and 87% non-Hispanic white. A guideline-based regimen (a macrolide, ethambutol, and rifamycin, with or without amikacin) was prescribed for 51% of new MAC therapy users at treatment start, of whom 41% were continuing guideline-based therapy at 6 months, and only 18% at 12 months. Of all new MAC therapy users, by 18 months only 11% were still receiving MAC treatment, 55% had discontinued therapy, and 34% were censored owing to death or the end of the study period. CONCLUSIONS: Overall, nearly half of new MAC therapy users were prescribed a non-guideline-recommended macrolide-based therapy, including regimens commonly associated with promoting macrolide resistance. Treatment discontinuation was common, and once discontinued, only a few beneficiaries resumed therapy at a later time. Our study adds important data to the current literature on treatment patterns for MAC-PD among older US populations. Future research should examine treatment patterns using more contemporary data sources.

ADP-ribosylation-resistant rifabutin analogs show improved bactericidal activity against drug-tolerant M. abscessus in caseum surrogate.

Necrotic lesions and cavities filled with caseum are a hallmark of mycobacterial pulmonary disease. Bronchocavitary Mycobacterium abscessus disease is associated with poor treatment outcomes. In caseum surrogate, M. abscessus entered an extended stationary phase showing tolerance to killing by most current antibiotics, suggesting that caseum persisters contribute to the poor performance of available treatments. Novel ADP-ribosylation-resistant rifabutin analogs exhibited bactericidal activity against these M. abscessus persisters at concentrations achievable by rifamycins in caseum.

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).

Systematic Review and Meta-Analysis on the Effects of Lactulose and Rifaximin on Patient-Reported Outcomes in Hepatic Encephalopathy.

INTRODUCTION: Patients with hepatic encephalopathy (HE) suffer from significant symptoms and impaired quality of life. Improved understanding on the potential benefits of first-line HE therapies may aid patient-provider discussions regarding expected benefits of HE treatments. We aimed to perform a systematic review to assess the effects of lactulose and rifaximin on patient-reported outcomes (PROs). METHODS: We searched MEDLINE, EMBASE, and Cochrane Library databases for randomized trials or prospective cohort studies using lactulose and/or rifaximin for the management of HE and assessing changes in PRO using PRO instruments. Physician reviewers independently reviewed titles, abstracts, and full texts and extracted data independently. We performed random-effects meta-analyses to examine the effects of lactulose and rifaximin on PROs. RESULTS: We identified 16 studies representing 1,376 patients that met inclusion criteria. Most studies assessed treatment of covert HE. In patients with covert HE, lactulose significantly improved overall patient-reported health-related quality of life measured by the Sickness Impact Profile with an estimated pooled mean difference of 6.92 (95% confidence interval: 6.66-7.18) and showed improvements in several subscales. Conversely, rifaximin demonstrated a nonstatistically significant mean difference in the total Sickness Impact Profile of 4.76 (95% confidence interval: -4.23 to 13.76), with strong evidence of heterogeneity between these studies. Studies examining other PRO instruments showed improvements in overall health-related quality of life, social functioning, and sleep from both lactulose and rifaximin. DISCUSSION: Patients with HE treated with lactulose or rifaximin reported improvements in important PROs. These results may inform provider-patient communication and help manage patient expectations regarding the potential benefits of HE therapies.

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.

Simultaneous Determination of Rifamycin Antibiotics and Their Active Metabolites in Human Plasma Using UHPLC-MS/MS to Evaluate Their Impact on Target Peak Concentrations: A Short Communication.

BACKGROUND: Standard and proper antituberculosis (anti-TB) treatment is essential for patients with TB, and rifamycin antibiotics are key components of anti-TB therapy. Therapeutic drug monitoring (TDM) of rifamycin antibiotics can shorten the time to response and complete treatment of TB. Notably, antimicrobial activities of the major active metabolites of rifamycin are similar to those of their parent compounds. Thus, a rapid and simple assay was developed for simultaneous determination of rifamycin antibiotics and their major active metabolites in plasma to evaluate their impact on target peak concentrations. Here, the authors have developed and validated a method for simultaneous determination of rifamycin antibiotics and their active metabolites in human plasma using ultrahigh-performance liquid chromatography tandem mass spectrometry. METHODS: Analytical validation of the assay was performed in accordance with the bioanalytical method validation guidance for industry described by the US Food and Drug Administration and the guidelines for bioanalytical method validation described by the European Medicines Agency. RESULTS: The drug concentration quantification method for rifamycin antibiotics, including rifampicin, rifabutin, and rifapentine, and their major active metabolites was validated. Significant differences in the proportions of active metabolites in rifamycin antibiotics may affect the redefinition of their effective concentration ranges in the plasma. The method developed herein is expected to redefine the ranges of "true" effective concentrations of rifamycin antibiotics (including parent compounds and their active metabolites). CONCLUSIONS: The validated method can be successfully applied for high-throughput analysis of rifamycin antibiotics and their active metabolites for TDM in patients receiving anti-TB treatment regimens containing these antibiotics. Proportions of active metabolites in rifamycin antibiotics markedly varied among individuals. Depending on the clinical indications of patients, the therapeutic ranges for rifamycin antibiotics may be redefined.

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.

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.