Amitiza is a brand name for the generic drug lubiprostone, a derivative of a naturally-occurring substance called prostaglandin E. In 2008, the United States Food and Drug Administration (FDA) approved Amitiza for the treatment of constipation-predominant irritable bowel syndrome (IBS). Many patients still refer to this condition by the older name of colitis, although experts have abandoned the term because it implies the existence of inflammation, which does not actually occur with irritable bowel syndrome.
Indications
Amitiza is indicated for the treatment of constipation-predominant IBS in women 18 and older. Clinical trials included too few men to provide conclusive evidence of benefit in this group, and Amitiza remains untested in children.
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, resulting in softer stools that pass more easily through the bowel.
Dosing and Administration
When used to treat IBS, doctors prescribe Amitiza as a capsule that should be swallowed whole. Patients take Amitiza twice each day, at morning and at night, preferably with food and water. Patients who miss doses should not double subsequent doses because this increases the risk of adverse effects.
Adverse Effects
In clinical trial data submitted to the FDA by the manufacturer, Sucampo Pharmaceuticals, the most common adverse effects of Amitiza were nausea, vomiting, diarrhea and abdominal distention. A small number of patients--0.04 percent of trial participants--experienced dyspnea, which means uncomfortable awareness of breathing. Although patients find dyspnea alarming and uncomfortable, it is not serious because it does not interfere with oxygenation.
Effectiveness
A 2009 review published in the journal "Drugs" concluded that most patients who took Amitiza experienced significant improvements in IBS symptoms such as constipation and abdominal pain as well as normalization of health-related quality of life. For some patients who completed a four-week course of treatment, these benefits were sustained even after the drug was discontinued.
References
- Food and Drug Administration: Amitiza (Lubiprostone) Capsules
- "Drugs;" Lubiprostone in Constipation-Predominant Irritable Bowel Syndrome; N.J. Carter and L.J. Scott; 2009
