Intestinal Adsorbent Offers Promise for Irritable Bowel Syndrome With Diarrhea

Laird Harrison

May 24, 2022

SAN DIEGO – An intestinal adsorbent, polymethylsiloxane polyhydrate (PMSPH), may relieve the diarrhea associated with irritable bowel syndrome (IBS), researchers say.

The adsorbent reduced abdominal pain, improved stool consistency, and won praise from patients, said Yan Yiannakou, MBChB, a consultant in gastroenterology at County Durham and Darlington (England) National Health Service Foundation Trust.

"It's great to have something new for patients to try," he told MDEdge. "And it's great that this treatment is so safe, and easy to use."

Yiannakou presented the finding at the annual Digestive Diseases Week (DDW).

Many people with irritable bowel syndrome find the currently available treatments and diets difficult to use or ineffective.

First developed 30 years ago in Eastern Europe, PMSPH is marketed over the counter in 30 European countries under the name Enterosgel as a treatment for diarrhea, said Yiannakou. It received conformité européenne (CE) mark in 2011.

Since PMSPH is not adsorbed by the body, it has been approved as a medical device rather than as a drug, said Yiannakou. Although its manufacturer is not yet marketing it in the United States, websites there are offering it as a dietary supplement for "toxin binding" and "cleansing the gut."

Since the etiology of IBS is poorly understood, it is also not clear exactly how PMSPH improves IBS symptoms, Yiannakou said. "I think this is binding a whole range of molecules which are either irritant or induce diarrhea through secretion." Fat, bile salts, immune chemicals, and bacterial breakdown products are possibilities, he said.

PMSPH's approval in Europe rests largely on trials for other forms of diarrhea; it did not undergo a high-quality randomized, placebo-controlled trial for IBS, Yiannakou said.

To fill that gap, he and his colleagues recruited 440 people with IBS, aged 16-75 years, from 28 sites in England. They randomly assigned 219 to receive PMSPH and 221 to receive a placebo for 8 weeks. Following this blinded phase, both groups received PMSPH for another 8 weeks (a phase requested by the patients who helped design the trial). The investigators then followed up with a phone call 8 weeks later to those who responded to the treatment.

The subjects recorded their symptoms in an e-diary and completed questionnaires. Because of COVID-19 constraints imposed after the trial began, the researchers collected some of the data through virtual visits and online questionnaires.

On a U.S. Food and Drug Administration–recommended composite score for abdominal pain and stool consistency, 37.4% of the patients receiving PMSPH were defined as responders versus 24.3% of the patients receiving the placebo, a statistically significant difference.

However, that score does not accurately reflect the main concerns of people with IBS diarrhea, said Yiannakou. More important is how often they have diarrhea, and by that measure the difference between the placebo and treatment groups was larger.

There were also statistically significant differences in favor of the PMSPH group in separate scores for abdominal pain, stool frequency, bloating, and urgency.

Surveyed between week 5 and week 8, 69% of patients taking PMSPH reported that they were getting adequate relief, compared with 30% of those taking the placebo. Among the responders surveyed 8 weeks after the open-label phase ended, 74% said they were still benefiting from the treatment. And 81% said they were still using PMSPH, even though they had to buy it for themselves.

Only a handful of patients experienced any adverse events, and there were no significant differences in the number of these events between those taking the placebo and those taking PMSPH.

"I think we're going to be eager to learn which patients that have irritable bowel syndrome would benefit from this particular treatment," said session comoderator Eric Shah, MD, MBA, director of gastrointestinal motility at Dartmouth University in Hanover, N.H., who was not involved in the study. He also wanted to know how PMSPH compares to similar binding agents on the market.

Session comoderator Nikrad Shahnavaz, MD, an associate professor of medicine in the division of digestive diseases, department of medicine, at Emory University, Atlanta, said his patients complain two binding agents now prescribed for IBS in the United States, cholestyramine and colestipol, cause nausea and vomiting. That could be an advantage for PMSPH, he said. "It's good to add to your tools."

Yiannakou, Shahnavaz, and Shah reported no relevant financial interests.

This article originally appeared on MDedge.com, part of the Medscape Professional Network.

An earlier version of this article misstated PMSPH's mechanism of action. It is not adsorbed by the body. Additionally, the marketing status of PMSPH was misstated; it is not currently on the U.S. market.

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