Ketotifen in atopic asthma and exercise-induced asthma.
The efficacy of ketotifen, a tricyclic benzocycloheptathiophene derivative, was assessed in an outpatient clinical trial and in a group of 12 asthmatic subjects with exercise-induced asthma. Subjects in the outpatient trial had mild asthma and consisted of two groups: a group of 24 atopic asthmatics with at least one positive skin test reaction and with an associated history of bronchial reactivity to at least one allergen; and a group of eight asthmatics with one or more positive skin prick tests but not bronchial reactivity to an allergen. Both groups took four weeks medication of ketotifen 1 mg bd and placebo in a randomised double-blind crossover study. There was no difference between ketotifen and placebo for any measurement made during the study and consequently no evidence of drug efficacy. The exercise study followed a standardised protocol and each subject took in random double-blind order, placebo, 1 mg, 2 mg, and 4 mg ketotifen two hours before exercise. There was no difference in the mean decreases in lung function from pre-exercise baseline values after three doses of ketotifen than with placebo. Drug levels suggested ketotifen was well absorbed. It would appear that if given for a period of only four weeks ketotifen had no beneficial effects in the management of mild asthma, and that a single dose before exercise does not modify exercise-induced asthma.