The U.S. Food and Drug Administration, known as the FDA, approved Amitiza---generic name lubiprostone---for the treatment of chronic idiopathic constipation in 2006 and constipation-predominant irritable bowel syndrome in 2008. Additionally, documented "off-label" uses of Amitiza include the treatment of opioid-induced constipation and constipation in the elderly and people with cystic fibrosis. Most patients who take Amitiza for constipation experience resolution of abdominal distention, or abdominal inflation; however, in rare cases, abdominal distention may occur as an adverse effect of Amitiza.
Mechanism of Action
The FDA classifies Amitiza as a chloride channel activator because it opens a specific chloride channel, ClC-2, in the cells that line the intestine, resulting in increased fluid within the intestine. For most people, this means softer stools that pass more easily through the intestine. In rare cases, the additional fluid causes diarrhea, abdominal distention, or both.
Amitiza as a Treatment for Abdominal Distention
Constipation causes abdominal distention---both the sensation of fullness and actual increases in abdominal girth---when stool and gases accumulate in the colon and rectum. In an April 2010 study published in the journal Digestive Diseases and Sciences, gastroenterologists at Wake Forest University found that Amitiza usually produced relief within 24 hours of initiating treatment.
Amitiza as a Cause of Abdominal Distention
In clinical trials submitted to the FDA by the manufacturer, Sucampo Pharmaceuticals, 6 percent of patients with chronic idiopathic constipation who took 24-micrograms of Amitiza two times per day reported abdominal distention, compared to 2 percent of patients who took a placebo. For constipation-predominant irritable bowel syndrome, 3 percent of patients experienced abdominal distention while taking 8-micrograms of Amitiza two times per day compared to 2 percent of patients who took a placebo.
At-Risk Groups
According to the FDA, Sucampo Pharmaceuticals' data also shows that men and people over 65 experience gastrointestinal adverse effects of Amitiza less frequently than women and people under 65. Since the mean age of participants in the chronic idiopathic constipation trials was 49.7 and the mean age in the irritable bowel syndrome trials was 46.5, younger patients may experience higher rates of adverse effects than those suggested by the clinical trials.
Management of Adverse Effects
Taking Amitiza with food and water may improve abdominal distention and other gastrointestinal side effects of Amitiza. If this fails, results from the clinical trials suggest that taking Amitiza once each day instead of twice may help.
References
- Food and Drug Administration: Amitiza (Lubiprostone) Capsules
- "Digestive Diseases and Sciences;" Efficacy and Safety of Lubiprostone in Patients with Chronic Constipation; C.F. Barish, D. Drossman, J.F. Johanson et al.; Apr. 2010
