Ketotifen in the prophylaxis of bronchial asthma.

The pharmacodynamic effects of ketotifen, a benzocycloheptathiophene derivative, on several partly interdependent biological pathways (calcium fluxes in excitable cells, production and release of mediators, mainly SRS-A, smooth-muscle contractility, density and sensitivity of adrenergic receptors) may be relevant to its antianaphylactic and asthma-prophylactic properties. Pharmacological investigations in humans of various target organs (skin, nasal mucosa, bronchi) have shown that ketotifen has strong antihistaminic and antianaphylactic effects. Its inhibiting action on bronchial responsiveness is not limited to bronchospasm induced by allergens but includes certain types of bronchial hyper-reactivity in which known mediators of allergy do not seem to be involved. Some important features of oral asthma prophylaxis with ketotifen are underlined. These include responder rate in both extrinsic and intrinsic asthma, pharmacokinetics and dosage in children, reduction in the consumption of corticosteroids and bronchodilators, and avoidance of side effects.