Lubiprostone (Amitiza): Chloride channel activator approved for the treatment of irritable bowel syndrome with constipation

New indication: Lubiprostone (Amitiza), a chloride channel activator, was approved on April 29, 2008, for the treatment of irritable bowel syndrome with constipation (IBS-C) in women aged at least 18 years.

Lubiprostone is a chloride channel activator that acts by increasing intestinal fluid secretion, thus increasing motility in the intestine, facilitating the passage of stool, and alleviating symptoms associated with constipation. This agent was approved on April 29, 2008, for the treatment of irritable bowel syndrome with constipation (IBS-C) in women aged ≥18 years.

Efficacy. The efficacy of lubiprostone for the treatment of IBS-C was evaluated in 2 double-blind, placebo-controlled studies of similar design. After a 4-week washout period, patients (N=1,154; 91.6% of study patients were women) were randomized to treatment with either lubiprostone 8 mcg twice daily or placebo for 12 weeks. The primary end point was assessed weekly by evaluating patients' responses to a global symptom relief question based on a 7-point balanced scale (responses ranged from "significantly worse" to "significantly relieved"). Monthly responders were defined as patients who had reported their symptoms as "significantly relieved" for ≥2 weeks of the month or at least "moderately relieved" for all 4 weeks of the month. Overall responders were defined as patients who met the criteria for monthly responders in ≥2 of the 3 months of the study. In Study 1, 13.8% of lubiprostone-treated patients were considered overall responders versus 7.8% of placebo-treated patients. In Study 2, 12.1% of lubiprostone-treated patients were considered overall responders versus 5.7% of placebo-treated patients; the treatment differences in both studies were statistically significant.

Safety. The safety of taking lubiprostone during pregnancy has not been evaluated; women who could become pregnant should therefore have a negative pregnancy test before initiation of therapy with lubiprostone and should be capable of complying with contraceptive measures. Lubiprostone treatment has been associated with nausea. Patients with severe diarrhea should not take lubiprostone. Diarrhea may occur during lubiprostone treatment. Lubiprostone treatment has been associated with dyspnea. Healthcare professionals should evaluate patients to confirm the absence of a mechanical gastrointestinal obstruction before therapy with lubiprostone is initiated. The most common adverse events associated with lubiprostone treatment include nausea, diarrhea, abdominal pain, and abdominal distension.