Antihistamines in the Treatment of Irritable Bowel Syndrome With Diarrhea

Trial details

Who runs it

University of Cincinnati

Trial code

NCT04612803

Record updated

4 September 2026

Original description

Irritable bowel syndrome is a functional disorder of the gastrointestinal tract diagnosed with the Rome criteria. The Rome IV criteria are based on abdominal pain symptoms and stool habits including stool frequency and stool forms [1]. They define 3 main subtypes based on symptoms: 1) IBS with diarrhea; 2) IBS with constipation: and 3) mixed symptoms of constipation and diarrhea. The IBS with diarrhea (IBS-D) subtype has the highest prevalence. Currently, treatment of IBS-D includes antidiarrheals, bile acid sequestrants, antispasmodics, tricyclic antidepressants, and FODMAP diet. However, many patients are intolerant or unresponsive to the above treatments. Outside of IBS, chronic diarrhea affects about 5% of adults. We have described a syndrome in a subset of IBS patients presenting with post prandial diarrhea, flushing and dermatographia whose symptoms are prevented by pre-treatment with combined H1 and H2 antihistamines [2]. However, the prevalence of this syndrome among the IBS + D patients is not known nor have the clinical characteristics or predictors of antihistamine responsive IBS + D been defined.Read full original descriptionShow less

Antihistamines in the Treatment of Irritable Bowel Syndrome With Diarrhea: a Cross-Over Trial

Irritable bowel syndrome is a functional disorder of the gastrointestinal tract diagnosed with the Rome criteria. The Rome IV criteria are based on abdominal pain symptoms and stool habits including stool frequency and stool forms [1]. They define 3 main subtypes based on symptoms: 1) IBS with diarrhea; 2) IBS with constipation: and 3) mixed symptoms of constipation and diarrhea. The IBS with diarrhea (IBS-D) subtype has the highest prevalence. Currently, treatment of IBS-D includes antidiarrheals, bile acid sequestrants, antispasmodics, tricyclic antidepressants, and FODMAP diet. However, many patients are intolerant or unresponsive to the above treatments. Outside of IBS, chronic diarrhea affects about 5% of adults. We have described a syndrome in a subset of IBS patients presenting with post prandial diarrhea, flushing and dermatographia whose symptoms are prevented by pre-treatment with combined H1 and H2 antihistamines [2]. However, the prevalence of this syndrome among the IBS + D patients is not known nor have the clinical characteristics or predictors of antihistamine responsive IBS + D been defined.

Inclusion: Age 18 years and older; Prior to Diagnosis of IBS + diarrhea based on ICD 10 codes with or without constipation unresponsive to prior treatments; Moderate to severe symptom severity score (>175 points) based on IBS symptom severity scale; Seeking evaluation by a health care professional; Negative serologic celiac panel; No response to lactose elimination diet by history; Normal colonoscopy; Able to complete symptoms diaries and global evaluations.

Exclusion: Current treatment with tricyclic antidepressants; Confirmed IgE dependent food allergy as a cause of the gastrointestinal symptoms; Celiac disease by serology; Inflammatory bowel disease or colitis; Post-surgical GI symptoms (e.g., dumping syndrome) by history; Current severe depression or history of psychosis; Lactose intolerance by history; Bile acid diarrhea by history; No colonoscopy performed; GI malabsorption; Current pregnancy.

ClinicalTrials.gov NCT04612803