Pharmacological evaluation of prophylactic anti-asthma drugs by reference to the pathological sequelae of exposure to allergen or platelet activating factor.

Exposure of guinea-pigs to platelet activating factor (PAF) induces airway hyperreactivity and causes an influx of eosinophils into the airways. These effects are inhibited by the established prophylactic anti-asthma drugs; cromoglycate, aminophylline, glucocorticosteroids and ketotifen, whereas other drug categories, with the exception of PAF-receptor antagonists, are ineffective.