Selective 5-HT2A receptor antagonist (Ki = 22 nM for at 5-HT2 receptors). Exhibits no affinity for 5-HT1A, 5-HT1B or 5-HT1D receptors. Inhibits collagen-induced serotonin secretion and platelet aggregation; displays no effect on serotonin uptake by platelets. Shown to inhibit arterial thrombus formation, but not venous thrombosis, in rat models. Purity 99%. MW (observed): 436.91