According to Dr. Chung Owyang, chief of gastroenterology at the University of Michigan, irritable bowel syndrome, also called IBS, afflicts 10 to 20 percent of people around the world and significantly impairs quality of life. Clinicians divide IBS into three subtypes: constipation-predominant, diarrhea-predominant and mixed. Amitiza, the brand name of the drug lubiprostone, treats the first subtype.
Indications
The Food and Drug Administration, or FDA, approved Amitiza in 2006 for the treatment of IBS in women older than 18 who suffer from constipation-predominant IBS. Amitiza has not been tested in children, and results in men have been disappointing.
Mechanism of Action
Amitiza selectively binds to chloride channels on the cells that line the intestine, resulting in increased transport of chloride into the bowel. Sodium and water follow passively, lubricating the passage of stool and decreasing intestinal transit time.
Dosing and Administration
When used to treat IBS, doctors prescribe Amitiza as an 8-microgram gelatin capsule that should be swallowed whole and never crushed. Patients take Amitiza two times each day, at morning and at night, preferably with food. Patients who miss doses should not double their next dose because the effectiveness of Amitiza for IBS depends on dose frequency rather than dose strength.
Side Effects
According to the FDA, the most common side effect of Amitiza is vomiting, which usually occurs when patients take the drug on an empty stomach. Less than 1 percent of people taking Amitiza complain of dyspnea--a feeling of chest tightness and difficulty breathing--beginning 30 to 60 minutes after taking the drug and usually resolving within three hours. The FDA does not categorize dyspnea as a “serious” side effect because, though uncomfortable and anxiety-provoking, dyspnea caused by Amitiza does not actually impair oxygenation.
Effectiveness
A 2009 review of all published clinical trial data for Amitiza in the treatment of constipation-predominant IBS concluded that most patients who took the drug experienced clinically significant reductions in IBS symptoms such as abdominal pain and constipation, as well as clinically significant increases in health-related quality of life. For some patients, these gains were sustained even after the drug was discontinued.
References
- Food and Drug Administration: Amitiza Prescribing Information
- “Harrison’s Principles of Internal Medicine, 17th edition;” A.S. Fauci, E. Braunwald, D.L. Kasper, S.L. Hauser, D.L. Longer, J.L. Jameson and J. Loscalzo (Eds.); 2008
- “Drugs;” Lubiprostone in Constipation-Predominant Irritable Bowel Syndrome; N.J. Carter and L.J. Scott; 2009
