Ketotifen (fumarate) is a second-generation noncompetitive H1-antihistamine and mast cell stabilizer, which is used to prevent asthma attacks.Target: Histamine Receptor Ketotifen is a second-generation noncompetitive H1-antihistamine and mast cell stabilizer. It is most commonly sold as a salt of fumaric acid,ketotifen fumarate, and is available in two forms. In its ophthalmic form, it is used to treat allergic conjunctivitis, or the itchy red eyes caused by allergies. In its oral form, it is used to prevent asthma attacks. Side effects include drowsiness, weight gain, dry mouth, irritability, and increased nosebleeds.Ketotifen relieves and prevents eye itchiness and/or irritation associated with most seasonal allergies. It starts working within minutes after administering the drops. The drug has not been studied in children under three. The mean elimination half life is 12 hours. Besides its anti-histaminic activity, it is also a functional leukotriene antagonist and a phosphodiesterase inhibitor. The drug may also help relieve the symptoms of Irritable bowel syndrome.

References:
[1]. Klooker TK, et al. The mast cell stabiliser ketotifen decreases visceral hypersensitivity and improves intestinal symptoms in patients with irritable bowel syndrome. Gut. 2010 Sep;59(9):1213-21.