Ineffective Pain Meds in IBS Patients Related to Immune System Changes

The presence of defects in the immune system in people with irritable bowel syndrome (IBS) is the major reason why sufferers have ongoing issues with pain, and one reason why some painkillers do not provide satisfactory relief to these patients, according to a recent study by researchers at the University of Adelaide, in Australia.

IBS is a functional gastrointestinal (GI) disorder leading to bowel changes, pain and discomfort. Studies estimate that IBS affects 3% to 20% of the adult population; however, only 5% to 7% of adults have been diagnosed, according to the U.S. National Institute of Diabetes and Digestive and Kidney Diseases.

IBS is often classified into four subtypes based on a person’s usual stool consistency: IBS with constipation (IBS-C), IBS with diarrhea (IBS-D), mixed IBS (IBS-M) and unsubtyped IBS (IBS-U). Although there are various forms, all involve unexplained gut pain, which often has the greatest impact on quality of life.

Scientists in the Nerve-Gut Research Laboratory, at the University of Adelaide, demonstrated the mechanisms involved in that pain, and the differences between the immune pain response in healthy people and in those with IBS. The gut contains monocytes and macrophages. In healthy people, these immune cells normally secrete opioid chemicals that block pain, but this opioid production is defective in patients with IBS.

“It is no wonder that people with IBS are experiencing ongoing periods of unexplained pain. And if the immune system is defective, it may also mean that painkilling medications taken to relieve their symptoms are not being adequately converted [by the body] to pain relief,” said Patrick Hughes, PhD, NHMRC Peter Doherty Fellow in the University of Adelaide’s School of Medicine.

The researchers obtained blood samples from more than 100 people, half with IBS and half without the condition. They analyzed the amount of endorphins and immune mediators that play a role in controlling pain, and found that these chemicals were deficient in subjects with IBS. The results were published online in Brain, Behavior, and Immunity (2014 July).

Although the exact cause of pain in IBS remains unknown, “we have now confirmed, and detailed, information about the important role of the immune system in this pain response,” said Dr. Hughes, who added that he hopes the work will lead to more targeted treatment for IBS.