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.