A comparison of the in vivo effects of ketotifen, clemastine, chlorpheniramine and sodium cromoglycate on histamine and allergen induced weals in human skin.

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Abstract
The effect of ketotifen was compared with that of clemastine and chlorpheniramine, known antihistamines, and sodium cromoglycate, a drug considered to have mast cell stabilizing properties on histamine and allergen wealing reactions in human skin, in random order, double-blind, placebo controlled studies. Ketotifen was significantly more potent in the inhibition of both histamine (P < 0.001) and allergen (P < 0.001) skin wealing reactions than either clemastine or chlorpheniramine. Sodium cromoglcyate had no significant effect on either histamine or allergen skin wealing reactions in any of the concentrations tested. Ketotifen, like clemastine, had a significantly greater inhibitory effect on histamine than on allergen induced weals (P < 0.001) and both drugs acted as competitive antagonists of histamine. Ketotifen is a potent anti-histamine but there is no evidence from these in vivo studies to suggest that it has any additional inhibitory activity on release of mediators from mast cells in human skin.