Inhibition of immediate hypersensitivity reaction by a new drug, RU-31156

The effects of RU-31156 on type I allergic reactions were studied and the following results were obtained. Seven-day homologous PCA in guinea pigs was significantly inhibited by oral doses of this drug. The maximum inhibition was observed when the drug was given 30 minutes prior to challenge. Forty-eight-hour homologous PCA was significantly inhibited in rats, and this inhibition was maximal when the drug was given 10 minutes prior to challenge. Orally-administered RU-31156 gave significant inhibition of induction of experimental asthma symptoms in guinea pigs when it was given one or two hours prior to challenge. In addition, the drug significantly inhibited the asthmatic reaction of experimental asthma in rats when it was given 10 minutes prior to challenge. RU-31156 significantly inhibited histamine and SRS-A release from the lung tissue of passively sensitized guinea pigs. The combined use of isoproterenol or theophylline with RU-31156 did not enhance the inhibitory activity of the drug. RU-31156 did not produce any effect on the histamine release induced by calcium ionophore A 23187. RU-31156 inhibited the Schultz-Dale reaction in the tracheal muscle and the ileum of guinea pigs, but it did not show any antihistaminic in these organs.