Researchers may have identified a reason for high sensitivity in the bowels of irritable bowel syndrome (IBS) patients. The finding may lead to new treatments, which could possibly help reduce abdominal pain associated with irritable bowel syndrome (IBS).

By studying the link between the substance histamine and pain receptor TRPV1, researchers from KU Leuven, Belgium, were able to identify histamine as a likely cause of heightened abdominal pain among these patients. The exact causes of hypersensitive pain receptors in IBS have long been unknown, though it is known that histamine exists in larger quantities in patients diagnosed with IBS than those who are not. 

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The researchers hypothesized that by blocking the histamine 1 receptor, they could prevent the sensitizing effect of histamine on the pain receptor TRPV1. They tested this by conducting a small pilot clinical study with the histamine receptor H1 (HRH1) antagonist ebastine — already found in hay fever medication — which blocks the histamine 1 receptor. The trial consisted of 55 IBS patients, 28 of whom were given 20mg/day of ebastine and 27 were given a placebo, for a total of 12 weeks.

Researchers assessed abdominal pain, symptom relief, and health-related quality of life each week. The study’s endpoint was effect of ebastine on the symptom score evoked by rectal distension.  They found that patients in the ebastine group reported significantly less abdominal pain than the placebo group. Reduced visceral hypersensitivity, increased symptom relief (ebastine 46% vs. placebo 13%; P=0.024), as well as reduced abdominal pain scores (ebastine 39±23 vs. placebo 62±22, P=0.0004) were seen in the ebastine vs. placebo group.

Although the results look promising, researchers acknowledge the study’s limitations due to its small database. They plan to conduct a follow-up study to test the efficacy of ebastine in 200 IBS patients.

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