The susceptibility of Helicobacter pylori to the rifamycin, rifaximin

Diverticular Disease and Rifaximin: An Evidence-Based Review

There have been considerable advances in the treatment of diverticular disease in recent years. Antibiotics are frequently used to treat symptoms and prevent complications. Rifaximin, a non-absorbable antibiotic, is a common therapeutic choice for symptomatic diverticular disease in various countries, including Italy. Because of its low systemic absorption and high concentration in stools, it is an excellent medicine for targeting the gastrointestinal tract, where it has a beneficial effect in addition to its antibacterial properties. Current evidence shows that cyclical rifaximin usage in conjunction with a high-fiber diet is safe and effective for treating symptomatic uncomplicated diverticular disease, while the cost-effectiveness of long-term treatment is unknown. The use of rifaximin to prevent recurrent diverticulitis is promising, but further studies are needed to confirm its therapeutic benefit. Unfortunately, there is no available evidence on the efficacy of rifaximin treatment for acute uncomplicated diverticulitis.

Effective therapeutic regimens in two South Asian countries with high resistance to major Helicobacter pylori antibiotics

Background

Nepal and Bangladesh have a high prevalence of Helicobacter pylori with high resistance rates to clarithromycin, metronidazole, and levofloxacin. Here, we evaluated the susceptibility and genetic mutations of 5 alternative antibiotics against isolates from both countries to obtain an effective treatment regimen for H. pylori eradication.

Methods

We used the agar dilution method to determine the minimal inhibitory concentration of 5 alternative antibiotics against 42 strains from Nepal and 56 from Bangladesh and performed whole genome mutation analysis.

Results

No resistance to furazolidone or rifabutin and a high susceptibility of sitafloxacin (95.2% in Nepal and 98.2% in Bangladesh) were observed. In contrast, resistance to rifaximin (52.4% in Nepal and 64.3% in Bangladesh) was high. Moreover, resistance to garenoxacin was higher in Bangladesh (51.6%) than in Nepal (28.6%, P = 0.041), most likely due to its correlation with levofloxacin resistance (P = 0.03). Garenoxacin and rifaximin were significantly correlated in Bangladesh (P = 0.014) and occurred together with all sitafloxacin-resistant strains. Mutations of gyrA could play a significant role in garenoxacin resistance, and double mutations of A87 and D91 were associated with sitafloxacin resistance. Analysis of the rpoB gene demonstrated well-known mutations, such as V657I, and several novel mutations, including I2619V, V2592 L, T2537A, and F2538 L.

Conclusions

Rifabutin can be cautiously implemented as therapy for H. pylori infection due to its interaction with the tuberculosis endemic in Bangladesh. The high susceptibility of furazolidone and sitafloxacin suggests their possible future application in Nepal and Bangladesh.

Therapeutic efficacy of amoxicillin and rifaximin in patients with small intestinal bacterial overgrowth and Helicobacter pylori infection

Introduction

Small intestinal bacterial overgrowth (SIBO) may coexist with Helicobacter pylori infection, which can be the cause of chronic gastrointestinal complaints.

Aim

Evaluation of the therapeutic efficacy of amoxicillin and rifaximin in the treatment of these diseases.

Material and methods

The lactulose hydrogen breath test (LHBT) and the urea breath test (¹³C-UBT) were performed in 116 patients. In 62 patients the coexistence of small intestinal bacterial overgrowth and H. pylori infection was observed. Then, in group I (n = 30) pantoprazole (2 × 40 mg), amoxicillin (2 × 1000 mg) and metronidazole (2 × 500 mg) and in group II (n = 32) pantoprazole and amoxicillin at the above doses and rifaximin (3 × 400 mg) were administered for 10 days. After 6 weeks, both breath tests were repeated and the degree of remission of symptoms was measured using a 10-point visual analog scale (VAS).

Results

After the treatment the LHBT index decreased in group I from 61.2 ±19.4 ppm to 22.0 ±8.2 ppm (p < 0.001) and in group II from 59.6 ±15.5 ppm to 15.2 ±8.6 ppm (p < 0.001). Eradication of H. pylori (¹³C-UBT below 4.0‰) was achieved in 63.3% of patients in group I and 59.4% in group II (p > 0.05). The decrease of pain below 3.0 points in the VAS was obtained in 64.8% of patients in group I and in 56.2% in group II.

Conclusions

Combination of amoxicillin and rifaximin may be effective in the treatment of patients with small intestinal bacterial overgrowth syndrome and concomitant H. pylori infection.

Efficacy and safety of rifaximin associated with standard triple therapy (omeprazole, clarithromycin and amoxicillin) for H. pylori eradication: A phase IV pilot clinical trial

BACKGROUND

A progressive decrease in Helicobacter pylori eradication rates has been described over the years, driving the need for new antibiotic treatments.

AIM

To evaluate the efficacy and safety of the addition of rifaximin (Spiraxin^®) to standard triple therapy (omeprazole, amoxicillin and clarithromycin) for the eradication of H. pylori.

METHODS

Independent prospective clinical trial (EUDRACT no.: 2013-001080-23). Forty consecutive adult patients were included with H. pylori infection, dyspeptic symptoms and naive to eradication treatment. A full blood test was performed in the first five patients enrolled to evaluate the safety of the treatment. H. pylori eradication was confirmed with the ¹³C-urea breath test at least four weeks after the end of treatment with rifaximin 400mg/8h, clarithromycin 500mg/12h, amoxicillin 1g/12h and omeprazole 20mg/12h for 10 days.

RESULTS

Forty patients were consecutively enrolled, 53% woman, mean age 44 years. Indication for eradication: 60% non-investigated dyspepsia, 38% functional dyspepsia and 2% gastric ulcer. Four patients did not attend the eradication confirmatory breath test. The eradication rate was 61% (95% CI: 45-77%) for the protocol and 55% (40-70%) for intention-to-treat. About 76% of the patients experienced adverse events (35% diarrhea, 14% nausea and 24% metallic taste), none of which was serious. The blood tests did not show significant alterations.

CONCLUSION

Acceptable H. pylori eradication rates are not achieved with rifaximin associated with standard triple therapy for 10 days.

Rifaximin Plus Levofloxacin-Based Rescue Regimen for the Eradication of Helicobacter pylori

Background/Aims

This study assessed the efficacy of a rifaximin plus levofloxacin-based rescue regimen in patients that had failed both triple and quadruple standard regimens for the eradication of Helicobacter pylori.

Methods

We treated patients for H. pylori between August 2009 and April 2011. The triple regimen consisted of combined treatment with amoxicillin, clarithromycin, and pantoprazole for 1 week. For failed cases, a quadruple regimen of tetracycline, metronidazole, bismuth dicitrate, and lansoprazole for 1 week was administered. The rescue regimen for persistently refractory cases was rifaximin 200 mg t.i.d., levofloxacin 500 mg q.d., and lansoprazole 15 mg b.i.d. for 1 week.

Results

In total, 482 patients were enrolled in this study. The eradication rates associated with the first and second regimens were 58% and 60%, respectively. Forty-seven out of 58 patients who failed with the second-line regimen received rifaximin plus levofloxacin-based third-line therapy. The eradication rate for the third regimen was 65%. The cumulative eradication rates were 58%, 85%, and 96% for each regimen, respectively.

Conclusions

A rifaximin plus levofloxacin-based regimen could be an alternative rescue therapy in patients with resistance to both triple and quadruple regimens for the eradication of H. pylori.

Rifaximin pharmacology and clinical implications

Rifaximin is a semisynthetic, rifamycin-based non-systemic antibiotic, with a low gastrointestinal absorption and a good antibacterial activity. The antibacterial action covers Gram-positive and Gram-negative organisms, both aerobes and anaerobes. Its antimicrobial action is based on its property to bind to the beta-subunit of bacterial DNA-dependent RNA polymerase inhibiting, thereby, the bacterial RNA synthesis. Rifaximin contributes to restore gut microflora imbalance, becoming an important therapeutic agent in several organic and functional gastrointestinal diseases such as hepatic encephalopathy, small intestine bacterial overgrowth, inflammatory bowel disease and colonic diverticular disease. This antibiotic has the advantage of low microbial resistance and few systemic adverse events and is safe in all patient populations, including young children.

Emerging therapies for the treatment of Helicobacter pylori infections

OBJECTIVE

To describe emerging therapies, such as levofloxacin, moxifloxacin, rifabutin, rifaximin, tinidazole, doxycycline, minocycline, lactoferrin, and plaunotol for the eradication of Helicobacter pylori infection.

DATA SOURCES

Relevant information was identified through a search of MEDLINE (1966-July 2008), PubMed (1955-July 2008), American Search Premier (1975-July 2008), International Pharmaceutical Abstracts (1960-2008), Science Citation Index Expanded (1996-2008), Cochrane Databases (publications archived until July 2008), and various tertiary sources using the terms Helicobacter pylori, fluoroquinolones, levofloxacin, moxifloxacin, rifabutin, rifaximin, lactoferrin, plaunotol, tinidazole, doxycycline, minocycline, faropenem, new treatments, refractory, and salvage alone or in combination.

STUDY SELECTION AND DATA EXTRACTION

Relevant information was identified and selected based on clinical relevance and value of information. In vitro and in vivo data were included if available.

DATA SYNTHESIS

Data exist supporting the use of levofloxacin or rifabutin as salvage therapies for H. pylori infection. Levofloxacin triple therapy has been recommended in the current treatment guideline, but more data are needed, especially from studies conducted in the US. A rifabutin-based regimen is better tolerated than conventional quadruple therapy, but its use is limited due to cost, hematologic adverse effects, drug interactions, and predicted development of resistance. Tinidazole appears to be an option, particularly as sequential therapy when combined with other agents; however, its use is limited by the high prevalence of nitroimidazole-resistant H. pylori strains in the US. Moxifloxacin data are limited. Data supporting the use of rifaximin, doxycycline, and minocycline are lacking or do not show benefit of these drugs over standard treatments.

CONCLUSIONS

H. pylori infection remains one of the most significant infections worldwide, and treatment failure rate with the current standard therapy continues to rise. Other treatment options should be explored to meet the emerging challenge.

Clinical application progress of Rifaximin in the treatment of digestive diseases

Rifaximin, a derivative of rifamycin, has high antibacterial activity on various kinds of Gram-positive and -negative aerobes and anaerobes, and it is a new drug in the treatment of giardiasis. Rifaximin is not easy to be absorbed after oral administration, and mild systemic adverse reaction is the main characteristic. Recently, Rifaximin has been widely and effectively used in the therapy of many diseases related to intestinal bacterial infection such as hepatic encephalopathy, diverticular disease, overgrowth of intestinal bacteria, inflammatory bowel disease (IBD) and H. pylori infection. The above advances were reviewed in the present article.

Rifaximin: a nonabsorbable rifamycin antibiotic for use in nonsystemic gastrointestinal infections

Rifaximin is a poorly water-soluble and minimally absorbed (<0.4%) rifamycin with in vitro activity against enteric Gram-negative bacteria including enteric pathogens. Fecal levels of the drug after 3 days' oral therapy exceed 8000 microg/g. Rifaximin is effective in the treatment and prevention of travelers' diarrhea due to Escherichia coli-predominant bacterial pathogens. It shows lower activity against dysenteric forms of bacterial diarrhea. The drug may be useful in other enteric infectious diseases, including Clostridium difficile colitis, pediatric bacterial diarrhea and Helicobacter pylori gastritis and chronic gastrointestinal disorders including hepatic encephalopathy, small bowel bacterial overgrowth, inflammatory-bowel disease, irritable-bowel syndrome and pouchitis. Importantly, rifaximin does not appear to lead to bacterial resistance. Rifaximin has an excellent safety profile and adverse drug reactions have been comparable to those associated with the placebo control agent.

Rifaximin: a novel nonabsorbed rifamycin for gastrointestinal disorders

Rifaximin, a virtually nonabsorbed (<0.4%) rifamycin drug, has in vitro activity against aerobic and anaerobic gram-positive and gram-negative microorganisms. Because rifaximin is nonabsorbed, systemic adverse effects are unusual, and after 3 days of therapy, the fecal level of the drug reaches 8000 microg/g. Moreover, the important selection of resistant mutants by the related drug, rifampin, has not yet been observed for rifaximin. Rifaximin has been demonstrated to reduce the duration of traveler's diarrhea secondary to noninvasive bacterial pathogens and recently has been shown to reduce the occurrence of the disease when used for chemoprophylaxis. Preliminary studies have demonstrated its potential for the treatment of other gastrointestinal disorders, such as hepatic encephalopathy. Additional studies should be performed to further define the role of rifaximin in the treatment of gastrointestinal diseases in adults and children.

Rifaximin-based regimens for eradication of Helicobacter pylori: a pilot study

BACKGROUND

Triple therapy is the treatment of choice for Helicobacter pylori-infected patients with an eradication rate ranging from 70 to 85%. Poor compliance and antibiotic resistance are the main causes of treatment failure. The aim of the present study was to assess the efficacy of rifaximin, a poorly absorbed antibiotic, for H. pylori eradication.

METHODS

We enrolled 48 consecutive H. pylori-positive patients affected. They were randomized to receive two 7-day rifaximin-based triple therapies: rifaximin tablets 400 mg t.i.d., esomeprazole 40 mg o.d. and clarithromycin 500 mg b.i.d. (CRE) or levofloxacin 500 mg o.d. (LRE). H. pylori eradication was assessed using a (13)C-urea breath test 4 weeks after the end of therapy. Treatment compliance and the incidence of side effects were also evaluated.

RESULTS

No dropouts were observed. The eradication rate both on intention-to-treat and per-protocol analysis did not show significant differences between groups: 58% (14/24 patients) in group 1 and 42% (10/24 patients) in group 2 (p = 0.24, OR 1.96, 95% CI 0.62-6.18). No significant differences in patients' compliance and incidence of side effects were found between groups.

CONCLUSIONS

Rifaximin-based therapy showed optimal compliance but a limited eradication rate compared to standard first-line treatment. Further investigations are needed to evaluate different dosages and combinations.

Rifaximin, a poorly absorbed antibiotic: pharmacology and clinical potential

Rifaximin (4-deoxy-4'-methylpyrido[1',2'-1,2]imidazo- [5,4-c]-rifamycin SV) is a synthetic antibiotic designed to modify the parent compound, rifamycin, in order to achieve low gastrointestinal (GI) absorption while retaining good antibacterial activity. Both experimental and clinical pharmacology clearly show that this compound is a nonsystemic antibiotic with a broad spectrum of antibacterial action covering Gram-positive and Gram-negative organisms, both aerobes and anaerobes. Being virtually nonabsorbed, its bioavailability within the GI tract is rather high with intraluminal and fecal drug concentrations that largely exceed the minimal inhibitory concentration values observed in vitro against a wide range of pathogenic organisms. The GI tract represents, therefore, the primary therapeutic target and GI infections the main indication. The appreciation of the pathogenic role of gut bacteria in several organic and functional GI diseases has increasingly broadened its clinical use, which is now extended to hepatic encephalopathy, small intestine bacterial overgrowth, inflammatory bowel disease and colonic diverticular disease. Potential indications include the irritable bowel syndrome and chronic constipation, Clostridium difficile infection and bowel preparation before colorectal surgery. Because of its antibacterial activity against the microorganism and the lack of strains with primary resistance, some preliminary studies have explored the rifaximin potential for Helicobacter pylori eradication. Oral administration of this drug, by getting rid of enteric bacteria, could also be employed to achieve selective bowel decontamination in acute pancreatitis, liver cirrhosis (thus preventing spontaneous bacterial peritonitis) and nonsteroidal anti-inflammatory drug (NSAID) use (lessening in that way NSAID enteropathy). This antibiotic has, therefore, little value outside the enteric area and this will minimize both antimicrobial resistance and systemic adverse events. Indeed, the drug proved to be safe in all patient populations, including young children. Although rifaximin has stood the test of time, it still attracts the attention of both basic scientists and clinicians. As a matter of fact, with the advancement of the knowledge on microbial-gut interactions in health and disease novel indications and new drug regimens are being explored. Besides widening the clinical use, the research on rifaximin is also focused on the synthesis of new derivatives and on the development of original formulations designed to expand the spectrum of its clinical use.

[Evaluation of Helicobacter pylori susceptibility to rifaximin]

INTRODUCTION

Helicobacter pylori infection affects more than half the world's population. It is a major cause of chronic gastritis and there is a strong association with peptic ulceration and gastric adenocarcinoma. Rifaximin is a new nonabsorbable broad-spectrum antimicrobial agent that reaches high concentrations in the gastrointestinal tract.

AIM

To evaluate the in vitro activity of rifaximin against H. pylori isolates.

METHODS

Thirty-one H. pylori strains were analyzed by the agar dilution method. Clarithromycin was used as the control antibiotic. Staphylococcus aureus and Streptococcus pneumoniae were used as quality control strains. Plates were read at days 4 and 7 of incubation. The MIC50 and MIC90 of each antibiotic were calculated. Strains with a clarithromycin MIC of > 1 microg/ml were considered resistant.

RESULTS

The MIC50 of clarithromycin at days 4 and 7 was 0.125 microg/ml and the MIC90 at days 4 and 7 ranged from 8 to 16 microg/ml, respectively. The MIC50 of rifaximin at days 4 and 7 ranged from 1 to 2 microg/ml, respectively, and the MIC90 was 4 microg/ml at both days 4 and 7. Twenty percent of H. pylori strains were resistant to clarithromycin. All clarithromycin-resistant strains were inhibited at a maximal rifaximin concentration of 4 microg/ml.

CONCLUSION

These results indicate that this new antibiotic may be useful for eradication of H. pylori infection. Because rifaximin is active against H. pylori strains resistant to clarithromycin, it could be useful in combination with this drug or in the treatment of therapeutic failure.

In vitro anti-Helicobacter pylori activities of new rifamycin derivatives, KRM-1648 and KRM-1657

The new rifamycin derivatives KRM-1657 and KRM-1648 were evaluated for their in vitro antimicrobial activities against 44 strains of Helicobacter pylori. Although the drugs were not very active against other gram-negative bacteria, the MICs at which 90% of isolates are inhibited for these drugs were lower (0.002 and 0.008 microgram/ml, respectively) than those of amoxicillin and rifampin for H. pylori. Time-kill studies revealed that the bactericidal activities of these agents were due to cell lysis. The results presented here indicate that these new rifamycin derivatives may be useful for the eradication of H. pylori infections.

Gastric diffusion of antibiotics used against Helicobacter pylori

Only a few pharmacological studies have been carried out on men and guinea pigs to determine the gastric diffusion of antibiotics, which are active against Helicobacter pylori. The results of these studies have been analysed in considering the physicochemical nature, the mode of administration, the way of gastric diffusion (topic and/or systemic) and the pharmacological interactions. The correlation of these pharmacokinetic results with those obtained in clinical trials is difficult because of the heterogeneity of the pharmacological and pharmacodynamic data. The absence of a convenient and suitable animal or in vitro study model renders further standardized pharmacokinetic studies in infected man and at steady state necessary.