ABSTRACT
This chapter presents classification & mode of action, indications & dermatological uses, formulations/presentation, dosages & suggested regimens, baseline investigations, considerations & monitoring, contraindications, cautions, important drug interactions, adverse effects & their management, use in special situations, and essential patient information of Antihistamines. Systemic antihistamines are commonly prescribed to relieve the symptoms of itch. Antihistamines are also useful in treating patients with allergic drug reactions and as an adjunct to adrenaline in the emergency treatment of anaphylaxis and histaminergic angioedema. H1 antihistamines are classified as first generation, which are sedating; and newer antihistamines which are relatively non-sedating, and include loratadine, desloratadine, cetirizine, levocetirizine, fexofenadine, acrivastine, bilastine, ebastine, mizolastine and rupatadine. H1 antihistamines are generally well-absorbed after oral administration. Prolonged use of H1 antihistamines may lead to some reduction in effectiveness, although tolerance of sedative effects of classical antihistamines is much more common than tachyphylaxis of antihistamine effects.
