Facile synthesis of 2-arylimidazo[1,2-a]pyridines catalysed by DBU in aqueous ethanol

A facile protocol for the synthesis of 2-arylimidazo[1,2-a]pyridines was developed using two-component cyclization of substituted 2-aminopyridines and substituted phenacyl bromides in 65–94% yield. The reaction was DBU catalysed using green solvent, aqueous ethanol (1 : 1 v/v) at room temperature. The atom economy of the products was calculated to be 66.25–73.41%. The developed protocol successfully exhibits a broad substrate scope, less reaction time, high to moderate yield and multigram scale synthesis.

Trial Evaluating Ambulatory Therapy of Travelers' Diarrhea (TrEAT TD) Study: A Randomized Controlled Trial Comparing 3 Single-Dose Antibiotic Regimens With Loperamide

Background

Recommended treatment for travelers' diarrhea includes the combination of an antibiotic, usually a fluoroquinolone or azithromycin, and loperamide for rapid resolution of symptoms. However, adverse events, postdose nausea with high-dose azithromycin, effectiveness of single-dose rifaximin, and emerging resistance to front-line agents are evidence gaps underlying current recommendations.

Methods

A randomized, double-blind trial was conducted in 4 countries (Afghanistan, Djibouti, Kenya, and Honduras) between September 2012 and July 2015. US and UK service members with acute watery diarrhea were randomized and received single-dose azithromycin (500 mg; 106 persons), levofloxacin (500 mg; 111 persons), or rifaximin (1650 mg; 107 persons), in combination with loperamide (labeled dosing). The efficacy outcomes included clinical cure at 24 hours and time to last unformed stool.

Results

Clinical cure at 24 hours occurred in 81.4%, 78.3%, and 74.8% of the levofloxacin, azithromycin, and rifaximin arms, respectively. Compared with levofloxacin, azithromycin was not inferior (P = .01). Noninferiority could not be shown with rifaximin (P = .07). At 48 and 72 hours, efficacy among regimens was equivalent (approximately 91% at 48 and 96% at 72 hours). The median time to last unformed stool did not differ between treatment arms (azithromycin, 3.8 hours; levofloxacin, 6.4 hours; rifaximin, 5.6 hours). Treatment failures were uncommon (3.8%, 4.4%, and 1.9% in azithromycin, levofloxacin, and rifaximin arms, respectively) (P = .55). There were no differences between treatment arms with postdose nausea, vomiting, or other adverse events.

Conclusions

Single-dose azithromycin, levofloxacin, and rifaximin with loperamide were comparable for treatment of acute watery diarrhea.

Clinical Trial Registration

NCT01618591.

Advantageous Solubility-Permeability Interplay When Using Amorphous Solid Dispersion (ASD) Formulation for the BCS Class IV P-gp Substrate Rifaximin: Simultaneous Increase of Both the Solubility and the Permeability

Rifaximin is a BCS class IV (low-solubility, low-permeability) drug and also a P-gp substrate. The aims of this work were to assess the efficiency of different rifaximin amorphous solid dispersion (ASDs) formulations in achieving and maintaining supersaturation and to investigate the consequent solubility-permeability interplay. Spray-dried rifaximin ASDs were prepared with different hydrophilic polymers and their ability to achieve and maintain supersaturation was assessed. Then, rifaximin's apparent intestinal permeability was investigated as a function of increasing supersaturation both in vitro using the parallel artificial membrane permeability assay (PAMPA) and in vivo using the single-pass rat intestinal perfusion (SPIP) model. The efficiency of the different ASDs to achieve and maintain supersaturation of rifaximin was found to be highly polymer dependent, and the copovidone/HPC-SL formulation was found to be superior to the other two, allowing supersaturation of 200× that of the crystalline solubility for 20 h. In vitro, rifaximin flux was increased and the apparent permeability was constant as a function of increasing supersaturation level. In vivo, on the other hand, absorption rate coefficient (k _a) was first constant as a function of increasing supersaturation, but at 250×, the crystalline solubility k _a was doubled, similar to the k _a in the presence of the strong P-gp inhibitor GF120918. In conclusion, a new and favorable nature of solubility-permeability interplay was revealed in this work: delivering high supersaturation level of the BCS class IV drug rifaximin via ASD, thereby saturating the drugs' P-gp-mediated efflux transport, led to the favorable unique win-win situation, where both the solubility and the permeability increased simultaneously.

Profile of rifaximin and its potential in the treatment of irritable bowel syndrome

Irritable bowel syndrome (IBS) is a chronic functional gastrointestinal disorder characterized by recurrent abdominal pain and abnormal bowel patterns. Alteration in gut flora, visceral hypersensitivity, and abnormal bowel motility are among numerous factors in the complex pathophysiology of IBS. Antibiotics have been used adjunctively to treat IBS for many years but are associated with various systemic side effects. Rifaximin is a nonabsorbable, broad-spectrum antimicrobial that inhibits bacterial RNA synthesis by binding the β-subunit of microbial RNA polymerase. It targets the gastrointestinal tract and works by reducing the quantity of gas-producing bacteria and altering the predominant species of bacteria present. In vivo animal studies suggest additional beneficial mechanisms of rifaximin, including reducing mucosal inflammation and visceral hypersensitivity. Clinical studies have demonstrated that rifaximin improves symptoms associated with IBS, such as bloating, flatulence, stool consistency, and abdominal pain, and has a side-effect profile similar to placebo. Although additional investigation into optimal dosing, treatment duration, and potential resistance is required, rifaximin presents as a safe and beneficial addition to the current management options for IBS.

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.

Comparative microbiological studies of transcription inhibitors fidaxomicin and the rifamycins in Clostridium difficile

Fidaxomicin (FDX) is a narrow-spectrum antibiotic for the treatment of Clostridium difficile-associated diarrhea. While FDX and rifamycins share the same target (RNA polymerase), FDX exhibits a unique mode of action distinct from that of rifamycins. In comparative microbiological studies with C. difficile, FDX interacted synergistically with rifamycins, demonstrated a lower propensity for the development of resistance to rifamycins, and exhibited no cross-resistance with rifamycins. These results highlight differences in the mechanisms of action of FDX and rifamycins.

Paediatric travel medicine: vaccines and medications

The paediatric aspects of travel medicine can be complex, and individual advice is often required. Nonetheless, children are much more likely to acquire common infections than exotic tropical diseases whilst travelling. Important exceptions are malaria and tuberculosis, which are more frequent and severe in children. Overall, travellers' diarrhoea is the most common illness affecting travellers. This review discusses vaccines and medications that may be indicated for children who are travelling overseas. It focuses on immunizations that are given as part of the routine schedule, as well as those that are more specific to travel. Malaria and travellers' diarrhoea are also discussed.

Treatment of Clostridium difficile infection: recent trial results

Clostridium difficile is a major cause of infection worldwide and is associated with increasing morbidity and mortality in vulnerable patient populations. Metronidazole and oral vancomycin are the currently recommended therapies for the treatment of C. difficile infection (CDI) but are associated with unacceptably high rates of disease recurrence. Novel therapies for the treatment of CDI and prevention of recurrent CDI are urgently needed. Important developments in the treatment of CDI are currently underway and include: novel antibacterial agents with narrower antimicrobial spectra of activity, manipulation of the gut microbiota and enhancement of the host antibody immune response.