Anti-allergy properties of PRD-92 Ea in guinea pig and rat.

The effects of PRD-92 Ea were examined on the increased plasma protein extravasation in the skin of guinea pig and rat elicited by specific antigens and spasmogenic mediators. PRD-92 Ea was found to be a potent inhibitor of rat PCA reactions when administered intradermally, intravenously or orally. This compound did not antagonize the local inflammatory responses of histamine, bradykinin or 5HT. This implies that in vivo PRD-92 Ea acts predominantly as an anti-allergy agent rather than a spasmogen antagonist. At high concentrations PRD-92 Ea directly increased vascular permeability when injected intradermally (greater than 250 micrograms/site) or administered by aerosol into the lung (greater than 10%). The importance of investigating such direct irritant actions of similar new drugs is discussed.