SUN-1334H free base, an orally active histamine H1 receptor inhibitor, exhibits a K_i of 9.7 nM and an IC 50 of 20.3 nM. Additionally, it effectively prevents histamine-induced contractions in isolated guinea-pig ileum with an IC 50 of 0.198 µM. The compound also blocks histamine-induced bronchoconstriction and skin wheals in guinea pigs and beagle dogs, respectively, and mitigates ovalbumin-induced rhinitis in guinea pigs.
