Research highlights IBS drugs offering best risk-benefit odds

Based on analysis of more than two dozen major clinical trials, two well-studied drug therapies – rifaximin and lubiprostone – offer irritable bowel syndrome (IBS) patients the best odds of benefit without harmful side effects, according to research led by the GI Motility Lab at Cedars-Sinai Medical Center in New York.

Led by Motility Lab Director Mark Pimentel, MD, the team published their findings online Mar 26 in The American Journal of Medicine.

“For the millions of patients who suffer from IBS [one in five US adults], effective treatment options have been very scarce,” Dr. Mark Pimentel says. Patients with IBS may experience a diarrheal form of the condition, a constipational form, or some combination, he explains. Frequent symptoms include abdominal pain or cramps, excess gas or bloating and visible abdominal distension.

Many Therapies Involve Side Effects

But drug therapies employed to treat IBS cause troubling side effects of their own, including nausea, insomnia, palpitations and decreased appetite. In an effort to sort out which treatments may provide benefits with the least risk of harm, the Cedars-Sinai team reviewed and compared the results of dozens of large-scale IBS drug trials.

For diarrhea forms of the condition, they evaluated:

• Tricyclic antidepressants;

• Alosetron, a drug that slows movement of stool in the gut;

• And rifaximin, an antibiotic that stays in the gut rather than disseminating into the blood stream and is currently FDA-approved to treat traveler’s diarrhea and hepatic encephalopathy.

For constipation forms of IBS, the researchers examined:

• Antidepressants known as serotonin reuptake inhibitors and

lubiprostone, a drug that promotes gut secretion.

The Research Found Striking Differences

On the one hand:

•  For every 2.3 patients who benefited from tricyclic antidepressants, 1 suffered harmful side effects and had to stop taking the medication.

•  For every 2.6 patients helped by alosetron, 1 had to halt the drug.

By contrast:

•  For every 846 patients aided by rifaximin, 1 had to discontinue the medication.

•  Lubiprostone and serotonin reuptake inhibitors demonstrated a complete lack of “harm” to IBS patients with constipation, as defined by the study.

“We found that rifaximin and lubiprostone have the lowest level of harmful side effects of all the well-studied drug therapies for IBS,” says Dr. Pimentel. “This underscores the need for us to continue to monitor new therapies for this disease,” he adds. “While it is important to see benefit with drugs, harm is something we do not often assess well.”

Besides Cedars-Sinai, other centers participating in the research included the School of Medicine at Texas Tech University’s Health Sciences Center; the UCLA Department of Medicine; Beth Israel Deaconess Medical Center; and Harvard Medical School. Funding for the study was provided by the Beatrice and Samuel A. Seaver Foundation.

The researchers note that: Dr. Pimentel discovered the use of rifaximin for IBS. Cedars-Sinai holds patent rights to the discovery and has a licensing agreement with Salix Pharmaceuticals Inc., which markets the drug. Dr. Pimentel is a consultant to Salix and serves on its scientific advisory board. None of the authors is affiliated with lubiprostone maker Takeda Pharmaceuticals or other drugs that were evaluated.

Source: Based on Cedars-Sinai Medical Center press release, Mar 26, 2012

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