N-benzylpiperazino derivatives of 3-nitro-4-hydroxycoumarin with H1 antihistamine and mast cell stabilizing properties.

In a small range finding study a number of N-benzylpiperazino derivates of 3-nitro-4-hydroxycoumarin have been shown to combine potent H1-antihistamine activity with that of mast cell stabilization as demonstrated by their activity as antagonists of histamine on guinea pig ileum and by their inhibition of the release of histamine in rat passive peritoneal anaphylaxis (PPA). The most potent compound, 1-[2-hydroxy-3-[(4-hydroxy-3-nitrocoumarin-7-yl)oxy]propyl]-4- (4-chlorobenzyl)piperazine, 30, had a pA2 of 9.0 against histamine on guinea pig ileum and inhibited histamine release in the rat PPA test with a potency similar to that of disodium cromoglycate.