- Peripheral blood leukocytes (PBL) from asthmatic individuals lose their former ability to adhere to glass when incubated with leukotriene C4 (LTC4). A modified leukotriene-induced leukocyte adherence inhibition (LAI) assay was therefore used to study the ability of anti-asthmatic drugs to abrogate such activity. Ketotifen, disodium cromoglycate, Verapamil, and dimethpyridene, all at concentrations of 2 X 10(-6) M, were co-cultured with 2 X 10(-7) M LTC4 and their effect on the LTC4-induced LAI determined. Verapamil, Ketotifen, and disodium cromoglycate all inhibited the LTC4 activity while the H1 antagonist, dimethpyridene, did not. These results suggest that the beneficial effect of Verapamil, Ketotifen, and disodium cromoglycate in bronchial asthma is probably as calcium antagonists that cause the inhibition of leukotriene activity.