It might make a good subject for toilet jokes, but for millions of people with irritable bowel syndrome, there is nothing remotely funny about the disorder.
Now scientists believe they have a potential treatment that could put a smile on the faces of those suffering from at least one type of IBS, the kind characterized by repeated bouts of diarrhea as well as other symptoms typical of the ailment - bloating, abdominal pain and, yes, the socially dreaded flatulence.
Doctors commonly categorize IBS patients as constipation-predominant, diarrhea-predominant or having an alternating pattern of diarrhea and constipation. Overall, the disorder affects an estimated 15 to 20 per cent of the population in Canada, the U.S. and other developed countries and costs health-care systems billions of dollars each year.
In two studies involving more than 1,200 subjects with diarrhea-predominant IBS, researchers found that a two-week course of the antibiotic rifaximin helped relieve symptoms not only during treatment, but also for weeks after the medication was stopped.
Participants who were randomly assigned to receive the drug reported less bloating and abdominal pain, and improved stool consistency for up to 10 weeks, say the authors, whose paper is published in this week's New England Journal of Medicine.
About 40 per cent or more of subjects given the thrice-daily rifaximin pill had significantly diminished IBS symptoms compared to those given placebo, or dummy pills, the study found.
What's more, say the authors, the success of the treatment points to bacteria as a possible cause of irritable bowel syndrome marked by frequent diarrhea.
"This is basically the culmination of 10 years of work in the sense that this is the final proof that an antibiotic approach really works in irritable bowel syndrome," principal investigator Dr. Mark Pimentel, director of the Gastrointestinal Motility Program at Cedars-Sinai Medical Center, said from Los Angeles.
Some researchers believe IBS occurs because bacteria that normally colonize the colon, or large intestine, migrate up into the nutrient-absorbing small intestine, where there are usually few or no bacteria present, explained Pimentel. Rifaximin works by destroying the bacterial overgrowth.
"This antibiotic had all the perfect characteristics: it doesn't get into your bloodstream, it stays only in the gut," he said. "It doesn't kill the good bacteria of the stool because the stool really doesn't change. It mostly works in the small bowel where the abnormal bacterial colonization is suspected as the cause of IBS in this case."
Pimentel, who was born in Thunder Bay, Ont., and trained in Winnipeg, said the other important feature of the drug is that it doesn't appear to cause bacterial resistance, which has occurred with many antibiotics that are absorbed into the bloodstream and subsequently into other organs and tissues.
"So it really was the perfect storm of antibiotic for this particular indication," he said, noting that the medication is already approved for treating travellers' diarrhea and for a specific liver disease.
The research team, which includes scientists from centres across the U.S., notes that there are few treatment options for IBS, and those often prescribed - such as dietary changes and boosting fibre intake - don't work well for many patients. The same is true of drug therapies such as antidepressants or medications aimed at either slowing down or speeding up the digestive process.
"With this antibiotic treatment, the patients feel better, and they continue to feel better after stopping the drug," said Pimentel. "This means that we did something to strike at the cause of the disease."
The research team is also studying the drug in patients whose IBS is constipation-predominant, and results are expected in about a year, he said.
Dr. Lawrence Cohen, a gastroenterologist at Sunnybrook Health Sciences Centre in Toronto, said the notion that bacterial overgrowth plays a role in irritable bowel syndrome is not a new one, but it remains controversial.
Cohen, who was not involved in the research, said two recent studies that tested different antibiotics on IBS patients found no benefit from the treatment.
He said rifaximin could have potential, although how much is difficult to determine because the difference in the proportion of those reporting symptom relief in the study's treated group versus the placebo group wasn't that dramatic.
"It's statistically significant, yes. But is it clinically significant?"
Cohen suggested that other causes of diarrhea-predominant IBS-like symptoms - including celiac disease, lactose-intolerance, inflammatory bowel disease or underlying cancer - would need to be ruled out before doctors consider the drug as a possible treatment.
"So it's not a clear-cut story."
While the findings shouldn't be dismissed, Cohen said he is cautious about the study because it was designed and funded by rifaximin's maker, Salix Pharmaceuticals Inc., a fact disclosed by the researchers. Pimentel discovered the use of rifaximin for IBS, and Cedars-Sinai holds patent rights to this discovery and has licensed those rights to Salix.
