Amitiza is the first FDA-approved prescription drug therapy for IBS-C. But it isn't a new drug. The FDA approved Amitiza in 2006 to treat chronic constipation in adults. The Amitiza dose used to treat IBS-C is lower than the dose used to treat chronic constipation.
Irritable bowel syndrome is a disorder characterized by cramping, abdominal pain, bloating, constipation, and diarrhea. IBS causes a great deal of discomfort and distress to its sufferers, and it affects at least twice as many women as men.
Amitiza works by increasing the secretion of intestinal fluid, which helps ease stool passage and constipation symptoms.
"For some people, IBS can be quite disabling, making it difficult for them to fully participate in everyday activities," Julie Beitz, MD, director for the Office of Drug Evaluation III at the FDA's Center for Drug Evaluation and Research, says in a news release. "This drug represents an important step in helping to provide medical relief from their symptoms."
The FDA approved Amitiza's use for treating IBS-C in women based on two studies involving 1,154 patients diagnosed with IBS-C, most of whom were women.
The patients either got Amitiza or a placebo pill. More patients in the Amitiza group than in the placebo group reported that their irritable bowel syndrome symptoms were moderately or significantly relieved over a 12-week treatment period.
The FDA didn't approve Amitiza for use in men. "The efficacy of Amitiza in men was not conclusively demonstrated for IBS-C," says an FDA news release.
Amitiza also isn't approved for use in children, and it shouldn't be given to patients who have severe diarrhea or known or suspected bowel obstructions. Amitiza's safety and efficacy haven't been established in pregnant women, nursing mothers, or patients with kidney or liver problems.
Amitiza's common side effects include nausea, diarrhea, and abdominal pain. Other rare side effects include urinary tract infections, dry mouth, fainting, swelling of the extremities, breathing problems, and heart palpitations.
The FDA recommends that Amitiza be taken with food and water twice daily in 8 microgram doses to treat IBS-C. Doctors and patients should periodically assess the need for continued therapy.
Amitiza is co-marketed by Sucampo Pharmaceuticals and Takeda Pharmaceuticals North America. Clinical trials are under way to test Amitiza for constipation in pediatric patients, people with liver problems, and treatment of opioid-induced bowel dysfunction.