May 27, 2015

Irritable bowel syndrome (IBS) is a chronic gastrointestinal disorder characterized by recurrent abdominal discomfort or pain that is accompanied by at least two of the following: relief by a bowel movement, change in frequency of stool, or change in consistency in stool. 

The following drugs have been approved recently:


Rifaximin is a semisynthetic antibiotic based on rifamycin.

The FDA approval of Xifaxan 550 mg is based on data from three phase 3 studies, TARGET 1, TARGET 2 and TARGET 3. Xifaxan 550 mg was studied in over 3,000 patients and demonstrated the efficacy and safety of repeat treatment following completion of a two-week course of treatment. A full course of Xifaxan 550 mg for IBS-D is available in a convenient 2 week pack of 42 pills.Recommended dosing for Xifaxan 550 mg for IBS-D is one 550 mg tablet three times a day for 14 days. 

Clostridium difficile-associated diarrhea (CDAD) has been reported with use of Xifaxan, and may range in severity from mild diarrhea to fatal colitis. If CDAD is suspected or confirmed, ongoing antibiotic use not directed against C. difficile may need to be discontinued. Use with caution in patients with severe (Child-Pugh Class C) hepatic impairment.

The most common adverse reactions for Xifaxan are peripheral edema, nausea, elevated liver enzymes (ALT), dizziness, fatigue, and ascites.


Viberzi (eluxadoline) has mixed opioid receptor activity, it is a mu receptor agonist, a delta receptor antagonist, and a kappa receptor agonist.

Efficacy was established in two Phase III clinical studies, demonstrating significant superiority over placebo on the composite endpoint of simultaneous improvement in both abdominal pain and diarrhea at both 75 mg and 100 mg twice daily doses. 

The most common adverse events in the two Phase III clinical trials were constipation (7% and 8% for eluxadoline 75 mg and 100 mg; 2% for placebo) and nausea (8% and 7% for eluxadoline 75 mg and 100 mg; 5% for placebo). Rates of severe constipation were less than 1% in patients receiving 75 mg and 100 mg eluxadoline. Rates of discontinuation due to constipation were low for both eluxadoline and placebo (=2%) and similar rates of constipation occurred between the active and placebo arms beyond 3 months of treatment.