Inhibition of dermographia, histamine, and dextromethorphan skin tests by ketotifen. A possible effect on cutaneous vascular response to mediators.

Forty-one subjects with dermographia were studied for a 4-week period. Twenty subjects received ketotifen therapy, the other 21 received chlorpheniramine (H1) for 2 weeks, and then chlorpheniramine plus cimetidine (H1 + H2). Both groups had significant suppression of dermographia and skin wheals caused by dextromethorphan and histamine after 2 weeks. The inhibition by ketotifen of dermographia, histamine wheal, and the dextromethorphan wheal increased from week 2 to week 4. During the first 2 weeks, ketotifen's activity was comparable to chlorpheniramine. Ketotifen's activity increased during the second 2 study weeks to match the additional chlorpheniramine. These results suggest that ketotifen may have additional pharmacologic activities besides H1 antagonism, including possible inhibition of mast cell mediator release. As a consequence, cutaneous vascular hyperresponsiveness may decrease. Ketotifen appears promising as treatment for allergic skin disorders.