The new findings are based on 26 studies that compared benefits and "harms" of five different drugs used to treat IBS, a condition in which patients experience stomach pain with either diarrhea or constipation.

"We do know that a lot of these drugs have side effects," said Dr. Mark Pimentel, the study's lead author and director of the Cedars-Sinai Medical Center's Gastrointestinal Motility Program in Los Angeles.

"They've been reported, but we didn't realize how bad it actually was -- specifically in the IBS population."

For their study, Pimentel's team looked at the number of patients who need to take a drug before one shows an improvement, and compared that to the number of patients who need to take it before one experiences a side effect.

For IBS with diarrhea, Pimentel and his colleagues analyzed past clinical trials of tricyclic antidepressants, a stool slower called alosetron and the antibiotic rifaximin.

From 19 studies, the researchers determined that about two people would benefit from tricyclic antidepressants before one patient was harmed, on average. About three patients would benefit from alosetron before one patient experienced harm, and 846 would benefit from rifaximin before one is harmed.

Side effects from the drugs could include dry mouth, flushing, palpitations, insomnia, constipation, stomach pain and other mild to serious symptoms.

While rifaximin appears to be the safest option for IBS patients, Dr. Ira Breite, a gastroenterologist at the New York University Langone Medical Center, said the study didn't answer one important question about the drug.

Breite, who was not involved in the new research, told Reuters Health that even if rifaximin is safe during treatment, nobody knows the long-term safety of antibiotics and what happens when you keep giving them.

One worry is that the more antibiotics are used, the more likely it is bacteria will become resistant to the drugs.

As for IBS with constipation, the group did not have as much information to work with and it was hard to make definitive conclusions, Pimentel told Reuters Health.

But the team writes in The American Journal of Medicine that both antidepressants known as selective serotonin reuptake inhibitors and the stomach drug lubiprostone "seem safe."

"This is not going to change any doctor's current approach to treating IBS," said Breite, who added that it confirmed what physicians have thought.

Breite also said there are other treatments for IBS aside from the medicines looked at in this report. They include probiotics -- bacteria thought to be beneficial for the gut, diet changes and talk therapy.

"Sometimes it's just a matter of reassurance that this will be okay," he said.

IBS cannot be traced to any specific physical condition. That makes it different from inflammatory bowel disease, including Crohn's disease, which can be diagnosed by a physical finding such as inflammation in the intestines.

Pimentel is a consultant for Salix Pharmaceuticals, the maker of the brand-name version of rifaximin, Xifaxan. Cedars-Sinai Medical Center also has a licensing agreement with the company. Another of the study's coauthors is a consultant for pharmaceutical companies Salix, Prometheus, Forrest and Alkermes.

SOURCE: bit.ly/GTcEns The American Journal of Medicine, online March 26, 2012.

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