Effect of ketotifen on phosphodiesterase activity from asthmatic individuals.

It was demonstrated, in this study, that phosphodiesterase activity was elevated in asthmatic patients compared to healthy individuals. This may be reason why various authors found higher intracellular cAMP levels in healthy individuals than in asthmatic patients. We also demonstrated that the efficacy of ketotifen in inhibiting antigen-specific histamine release is due to the potent inhibitor effect of ketotifen on cellular phosphodiesterase activity which then allowed intracellular cAMP accumulation, and as a consequence prevented mediators release.