Antiallergic action of disodium cromoglycate and xanthone RS 7540

Disodium cromoglycate (DSCG) and RS 7540 both inhibited the rat PCA reaction mediated by mouse IgE; RS 7540 was more potent. RS 7540 showed self- and cross-tachyphylaxis with DSCG and failed to protect rat mast cells against desensitization induced by antigen. In the guinea pig ileum test, DSCG reduced stimulation by various spasmogens, whereas RS 7540 even at high doses was inactive. These differences suggest that RS 7540 has major deficiencies as a potential alternative to DSCG in the treatment of bronchial asthma.