Purity >97%. Loratadine is a non-sedating antihistamine that acts as a selective inverse agonist of peripheral histamine H1 receptors (Ki = 35 nM). It has been shown to inhibit the release of leukotriene C4 (IC50 = 8 μM) and histamine (IC50 = 11 μM) from rodent mast cells and to inhibit allergic bronchospasm in guinea pigs with an ED50 value of 0.40 mg/kg.