the release of histamine in the rat peritoneal fluids by 50%: IC50 = 0.74 µM (rat); release of histamine in rat passive peritoneal anaphylaxis: IC50 = 0.74 µM (rat); antigen-induced release of histamine (AIR) by 50% from rat peritoneal mast cells (RMC) (in vitro): IC50 = 3 µM (rat); the release of extravasated dye in the rat peritoneal fluids by 50%: IC50 = 5.8 µM (rat); release of extravasation in rat passive peritoneal anaphylaxis: IC50 = 5.8 µM (rat)