Rupatadine (UR-12592, rupatadine) is a potent and orally available dual antagonist of PAF and histamine H1 receptors with Ki values of 0.55 μM and 0.1 μM, respectively, which provides relief of allergic symptoms and anti-inflammatory properties, and is used in allergic rhinitis and chronic urticaria.

H1 Receptor:0.1 μM (Ki), PAF:0.55 μM (Ki), PAF-induced platelet aggregation (human plasma):0.68 μM

Rupatadine acts as a dual H1 and PAF receptor antagonist. Rupatadine has a Ki of 0.10 μM for H1 and 0.55 μM for PAF receptors. Rupatadine competitively inhibits histamine-induced guinea pig ileum contraction (pA₂ = 9.29), and PAF-induced platelet aggregation in rabbit platelets (pA₂ = 6.68) and human plasma (IC₅₀ = 0.68 μM), without affecting ACh, 5-HT, or LTD₄ responses[1].

Rupatadine blocks histamine- and PAF-induced hypotension (ID₅₀ = 1.4 and 0.44 mg/kg i.v.) and bronchoconstriction (113 and 9.6 μg/kg i.v.). Rupatadine protects mice from PAF- and endotoxin-induced death (ID₅₀ = 0.31-3.0 mg/kg). In dogs, 1 mg/kg p.o. still inhibited vascular permeability >26 h. No sedation was observed at 100 mg/kg[1].