Astemizole is a synthetic piperidinyl-benzimidazol derivative with antiallergic properties, acts as a reversible competitive inhibitor of histamine H1 receptors, with less anticholinergic effects compared to related agents. It is a long-acting, non-sedative antihistaminic used in the treatment of seasonal allergic rhinitis, asthma, allergic conjunctivitis, and chronic idiopathic urticaria.