Visceral hypersensitivity in irritable bowel syndrome (IBS) has been associated with mast cell activation. In a recent study published in Gut, Belgian researchers tested whether mast cell stabilization would improve abnormal visceral perception. Sixty IBS patients underwent a barostat study to evaluate rectal sensitivity to distention. The patients were then randomized to receive ketotifen (a mast cell stabilizer) or placebo. Response was assessed through a questionnaire and a repeat barostat study. Rectal biopsies were also performed to measure tryptase and histamine levels.

Ketotifen was found to increase the threshold for discomfort in patients with visceral hypersensitivity, but not in normosensitive IBS patients. Ketotifen also decreased gastrointestinal symptoms and improved health-related quality of life.

Compared to healthy volunteers, IBS patients had greater histamine release and lower spontaneous release of tryptase. Ketotifen did not reduce tryptase release. It is therefore unclear whether ketotifen improves IBS symptoms via mast cell stabilization or an alternate mechanism, such as H₁ receptor antagonism.

• Source
• Klooker TK, Braak B, Koopman KE, Welting O, Wouters MM, van der Heide S, Schemann M, Bischoff SC, van den Wijngaard RM, Boeckxstaens GE. The mast cell stabiliser ketotifen decreases visceral hypersensitivity and improves intestinal symptoms in patients with irritable bowel syndrome. Gut 2010 Jul 21. [Epub ahead of print]