Inhibition of histamine release from human lung in vitro by antihistamines and related drugs

1 A series of cationic, lipophilic histamine H1-receptor antagonists, neuroleptics, antidepressants and Monoamine Oxidase inhibitors were tested for their effects on anti-IgE-induced histamine release from human lung fragments in vitro. 2 They had a biphasic effect: at low concentrations a dose-related inhibition of histamine release was observed whereas, at higher concentrations, the drugs liberated histamine even in the absence of antigen. 3 Mepyramine, a much less lipophilic drug than the Others tested, was only weakly active on mast cells at pharmacological concentrations. 4 The potency of the drugs as release inhibitors was not related quantitatively to their histamine liberating potency. 5 There was no; correlation between activity on mast cells and histamine H1-receptor antagonism. 6 Mast cell stabilization may play a part in the activity of these drugs as anti-allergic agents.