A new clinical study shows that Paxil, a type of drug called an SSRI, improves some irritable bowel symptoms. Although Paxil is mainly used to treat depression and anxiety, none of the patients in this study suffered from depression. In fact, says study leader George Arnold, MD, of the University of Pittsburgh Medical Center, patients with no hint of depression responded well to the drug.
The cleverly designed study showed that more than one in four irritable-bowel patients get enormous relief simply by going on a high-fiber diet.
"On just the high-fiber diet, 26% of the people who were having a lot of symptoms felt well enough that they didn't want anything more done," Arnold says. "Their pain and their bloating improved, and their overall well-being improved enough to say they didn't want any more treatment."
When Fiber Fails
Not everybody with irritable bowel syndrome gets better after going on a high-fiber diet. In the Arnold team's study, those who didn't get better with a high-fiber diet went on to the second part of the study. The 81 patients in this part of the trial were randomly assigned to get Paxil or an identical-looking placebo for 12 weeks. Neither the patients nor their doctors knew which drug they were taking.
Nearly two thirds of the Paxil group -- 63.3% -- reported improvement in their overall well-being. Only 26.3% of the placebo group reported this kind of improvement. Paxil didn't help with abdominal pain or bloating. But patients who took Paxil had significantly better improvement in other symptoms -- straining, urgency, and a feeling of incomplete evacuation -- than those who took a placebo.
At the end of the 12 weeks, patients could choose to continue on their medication -- without learning whether they were taking Paxil or placebo. In the Paxil group, 84% wanted to continue. Only 37% of the placebo group chose to continue treatment. After six months, 76% of the Paxil group and 36% of the placebo group were still taking their pills.
These findings impress Reza Shaker (sha-CARE), MD, chief of the division of gastroenterology and hepatology at the Medical College of Wisconsin.
"It is an interesting study, and I think it is a real effect of Paxil they are seeing," Shaker tells WebMD. "I like this study because it is independent -- the drug companies did not pay for it -- because it was randomized, and because it has a six-month follow-up. It's a relatively small number of patients, but still it is very promising that in a subgroup of IBS patients, SSRI antidepressants may be helpful."
Irritable bowel syndrome, Shaker says, is not a single disease but may arise from several as-yet-unknown causes. By treating only patients who did not respond to fiber, he suggests, Arnold's team may have found a way to identify a group of patients with the kind of irritable bowl syndrome most likely to respond to antidepressant treatment.
"Obviously we should not take this study as encouragement to give this drug to everybody," Shaker warns. "It must be used in a select group of patients."
Why would an antidepressant work in people who aren't depressed? Older tricyclic antidepressants are often used to treat irritable bowel syndrome. But newer antidepressants -- the SSRI class, like Paxil -- specifically act to increase the action of serotonin, a chemical messenger.
The drugs are designed to increase serotonin levels in the brain. But that's not the only place serotonin is found.
"Here's why I think Paxil works for irritable bowel: 95% of the serotonin in the body is in the intestine," Arnold says. "I think it is doing something to the nerves in the gastrointestinal tract."
Shaker notes that people with irritable bowel syndrome tend to have problems with the way sensations arise in the gut, the way these sensations travel through the nerves to the brain, and/or with the way the brain processes these signals. He agrees that Paxil and other SSRIs are likely to affect this process.
"In future, there may be objective tests to tell which irritable-bowel patients have neural processing problems," Shaker says.
Arnold suggests that many patients may benefit from SSRI antidepressants such as Paxil. Indeed, he and Shaker note that many doctors already prescribe the drug for selected irritable-bowel patients.
"If you've got irritable bowel syndrome and are not on a high-fiber diet, you should be," Arnold says. "If that doesn't work after six weeks, try a trial of Paxil. Understand we are nottreating depression. But the drug is safe [when taken under medical supervision], and most patients will feel better."
Arnold and colleagues' study appears in the May issue of the American Journal of Gastroenterology.