Asimadoline in the treatment of irritable bowel syndrome

Importance of the field: Irritable bowel syndrome (IBS) represents one of the most common gastrointestinal disorders, with the diarrhea-predominant form (D-IBS) representing an area of high unmet medical need. One difficulty in identifying suitable treatments for IBS is that although there are animal models for the components of IBS, it is not clear whether animals are afflicted by the disease. In a recently completed Phase II study, the kappa-opioid agonist, asimadoline, was shown to be efficacious in a prospectively defined subgroup of D-IBS patients. This study confirmed a good safety profile for asimadoline. Areas covered in this review: The chemistry, pharmacology, pharmacokinetics, pharmacodynamics and clinical safety and efficacy of asimadoline in relationship to IBS is reviewed. Papers were searched over the past 20 years using the PubMed database and key words 'asimadoline', 'kappa-opioid agonist' and 'irritable bowel syndrome'. Abstracts were reviewed and appropriate full papers were then evaluated. What the reader will gain: The reader will gain an appreciation of kappa-opioid agonists as IBS treatments. Take home message: In a prospectively defined, clinically relevant patient subgroup, asimadoline shows efficacy in the treatment of D-IBS.