RENEE MONTAGNE, host:
Tens of millions of people suffer from a nasty disorder that can last for months and even years. It's called Irritable Bowel Syndrome. A new study published today suggests many of those people can be helped by taking an antibiotic for just two weeks. As NPR's Richard Knox reports, that is a new way of thinking about a disease that has lacked an effective treatment and has been widely blamed on stress.
RICHARD KNOX: There's not much question that psychological stress is involved in many cases of irritable bowel syndrome, or IBS. But for a while now, Dr. Mark Pimentel didn't think stress explained everything. He noticed most patients with IBS have abdominal bloating.
Dr. MARK PIMENTEL (Cedars Sinai Medical Center): And bloating has to be caused by something - gas production in the gut. And that's from bacteria.
KNOX: Pimentel, who works at Cedars Sinai Medical Center in Los Angeles, has been working on the idea that many people with IBS have an overgrowth of bacteria in the small intestine. Normally there's no bacteria there. So if bacteria are the problem, antibiotics might help.
It didn't work in early studies. But then Pimentel tried an antibiotic called rifaximin that kills many types of bacteria and causes almost no side effects. Studies in this week's New England Journal of Medicine show a two-week course of rifaximin works - at least for some patients.
Dr. PIMENTEL: Four in 10 patients will have adequate relief of their IBS as a result of this treatment.
KNOX: Forty percent sounds pretty good. But you have to realize that 30 percent of patients got substantially better when they took a placebo, thinking it might be an antibiotic. That's further evidence that IBS, for some people, has a strong psychological component. But there's something else about the new studies that suggests there's more than a placebo effect going on here - at least among the people for whom the antibiotic works at all.
Dr. PIMENTEL: Once rifaximin was finished after only 14 days, the patients continued to stay better through the entire 12 weeks of the study, even though they didn't need to take the drug any more. And that suggests that we weren't just treating symptoms, we actually touched on a cause of IBS, because they shouldn't have stayed better if it wasn't for that reason.
KNOX: There are no studies yet to show how long it works. Some people relapse in a few months. But Pimentel has seen patients who have long-lasting relief. Patients like Amy McMahon, a Southern California woman who woke up one day with IBS.
AMY MCMAHON: It looked like I was about six months pregnant, just overnight. So it was alarming.
KNOX: The unpredictable symptoms of IBS also changed her life.
MCMAHON: First and foremost, when you get up and you're planning your day, you had to think about what can I possibly do today? Should I go here or not? Am I going to feel good? Or how bad am I going to feel? Do I need to be near a toilet today?
KNOX: Doctors told her women her age, around 50, have bodily changes they just have to get used to. But eventually she tried Pimentel's antibiotic treatment.
MCMAHON: To my delight, after, I believe it was a 14-day treatment, I felt substantially better. I would say 60 to 70 percent better. It was remarkable.
KNOX: Some months later, McMahon had a relapse and took a second course of rifaximin. But since then, she's been mostly free of IBS symptoms. That was three years ago.
She's in the minority. So far, most patients don't benefit at all. But rifaximin is already approved for treatment of travelers' diarrhea, so some doctors are beginning to prescribe it for IBS. The drug's maker, which sponsored the new studies, is hoping the Food and Drug Administration will make it official and allow the company to market it for treatment of IBS. Currently it costs around $900 for a two-week course.
Richard Knox, NPR News. Transcript provided by NPR, Copyright NPR.
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