Tulopafant is a platelet activating factor (PAF) antagonist. In Vitro: Preincubation of neutrophils with Tulopafant (RP 59227) results in a concentration-dependent decrease in chemiluminescence produced by PAF primed cells^[1]. In Vivo: Tulopafant (RP 59227) effectively reduces myocardial infarct size and reduces the incidence of ischemia and reperfusion-induced arrhythmias in barbital-anesthetized dogs^[1].Histological examination reveals marked diminution of both interstitial hemorrhage and deposition of platelet and granulocytes in capillaries of cardiac xenografts when recipient animals are pretreated with Tulopafant^[2].