By Kathleen Doheny
WebMD Health News
Reviewed by Brunilda Nazario, MD
May 28, 2015 -- The FDA has approved two new prescription medications to treat irritable bowel syndrome with diarrhea, or IBS-D. It's the latest step in a years-long struggle to find safe and effective treatments for the condition.
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"I think patients with IBS should be very excited to have more options," says Lawrence Schiller, MD, program director of the gastroenterology fellowship at Baylor University Medical Center. "Neither drug is a miracle, but they are both likely to be helpful for some patients."
The two medications are Viberzi (eluxadoline) and Xifaxan (rifaximin). Viberzi helps you have fewer bowel contractions, which leads to less diarrhea. Xifaxan is an antibiotic that's thought to work by changing your gut bacteria and reducing diarrhea.
Irritable bowel syndrome (IBS) is estimated to affect up to 15% of Americans, or more than 45 million people, according to the National Institutes of Health. But only about half of those people have gotten diagnosed with the condition by a doctor. IBS affects about twice as many women as men, and it most often happens in those under age 45.
IBS isn't linked to more serious diseases like cancer, but the symptoms can be painful and may interfere with your daily life.
Filling a Need
In the past, people with IBS-D have had few good options. A drug previously approved to treat it was tightly restricted after safety issues came up.
Lotronex (alosetron), which works by slowing stool movement, was withdrawn from the market in 2000 after it was linked to reports of other gut problems, including severe constipation and ischemic colitis. In 2002, the FDA approved the availability of Lotronex through a restricted marketing program, meaning it can be prescribed only under certain circumstances.
Why are there so few safe IBS-D drug options? "I think it has to do with (the fact that) the biggest problem is, we don't fully understand the mechanism or cause of this," says Anthony Lembo, MD, director of the GI Motility and Functional Bowel Disorder Center at Beth Israel Deaconess Medical Center.
IBS can be treated several different ways. Diet and stress reduction can help, along with some over-the-counter medicines. Doctors can also prescribe antidepressants, which can help relieve belly pain, and antispasmodics, which can reduce bowel contractions.
People who don't have IBS tend to dismiss it as nothing serious, Schiller says, but symptoms like frequent diarrhea, constipation or both, along with bloating and belly pain, "can really wreck your life."
New IBS-D Options
You take Viberzi by mouth twice a day with food, according to the FDA. The agency approved it based on two clinical trials including more than 2,400 people, who were randomly given Viberzi or a placebo.
The active drug worked better to ease belly pain and improve stool consistency over the 26-week study.
You take Xifaxan by mouth three times a day for 14 days, the FDA says. If symptoms come back, another 14-day course can be taken, up to two times.
The FDA approved the drug based on three different clinical trials including nearly 1,900 people. In two studies, those who took Xifaxan were more likely to say they had improvements in belly pain and stool consistency than those who took a placebo. In a third study, 636 patients whose IBS came back after treatment were given either another 14-day course or placebo. More of those on the active drug said they had less abdominal pain and better stool consistency.
What the Researchers Say
In general, Viberzi ''shows reasonably good response for the treatment of diarrhea and a modest response for the pain," says Douglas Drossman, MD, professor emeritus of medicine and psychiatry at the University of North Carolina, Chapel Hill. He's a gastroenterologist who is familiar with both drugs.
Viberzi ''has a significant effect on bowel frequency and consistency and also improves urgency," says Lembo, who was an investigator for studies on both drugs. The drug also improves abdominal pain, he says.
Xifaxan has been shown to produce adequate relief for IBS-related bloating and symptoms, Lembo says.
Because Xifaxan only works in the gut, Drossman says, "I don't think there are any real safety concerns."
The most serious known risk with Viberzi is a chance of spasm in a muscle surrounding the end of the common bile and pancreatic ducts, which can lead to pancreatitis, according to the FDA. For that reason, certain people shouldn't take it, including those with a history of bile duct problems, liver problems, or in those who have more than three alcoholic drinks a day, the agency says. Common side effects include nausea, constipation, and belly pain.
Nausea is also a common side effect for those on Xifaxan. They may also get an increase in a liver enzyme that can be measured in the blood, so doctors need to be cautious about prescribing the drug to people with a liver impairment, the FDA says.
Perspectives on New Meds
The drugs are meant to be used along with lifestyle changes, Lembo says. Here are some of those suggested changes, according to the American College of Gastroenterology:
- Limit foods that aggravate your symptoms, such as beans, cabbage, broccoli or onions.
- Eat more slowly, and avoid overeating.
- Avoid carbonated drinks, which can lead to gas and cramping.
When Will New Drugs Be Available?
Viberzi is a narcotic, so the Drug Enforcement Administration (DEA) has to determine its schedule status, according to David Belian, a spokesman for the drug's maker, Actavis. The DEA decides which of five categories or schedules a drug will be in, depending on abuse or dependency potential. Viberzi is expected to become available in early 2016. Belian couldn't provide any cost estimates.
Xifaxan, made by Salix, is already available in the same dosage to treat liver problems. Sixty tablets are about $1,700. It's expected to be covered by insurance to treat IBS-D, says Laurie Little, a spokeswoman for Valeant Pharmaceuticals International, which owns Salix.
Lembo reports consultancy work for Actavis, Salix, and Prometheus. Drossman has done consultant work for Furiex (now Actavis), Salix, and Actavis. Schiller reports consulting, advisory board and speaking engagements for Salix and Actavis.
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