DRUG EVALUATION Desloratadine: a review of pharmacology and clinical effi cacy in allergic rhinitis and urticaria

Over 80 million people in Europe are affected by some form of allergic disease, according to the Global Allergy and Asthma European Network estimates. Among these diseases, the prevalence of allergic rhinitis (AR) is increasing, and is estimated to be up to 39% in children and 40% in adults. A total of 70% of the cases occur before the age of 30 years. In addition to clinical symptoms including sneezing, nasal pruritis and rhinorrhea, AR signifi cantly reduces quality of life, and negatively impacts school and work performance. Each year, millions of people experience complications such as sinus disease and otitis media associated with AR. Furthermore, direct and indirect costs, including prescription treatments and lost productivity attributable to AR, exceed US$5.6 billion in the USA and €3 billion in Europe [1]. It has been estimated that up to 3.8 million school or work days are lost per year in the USA due to AR. The interrelation between rhinitis and asthma has been demonstrated in various studies [2–4]. In one study, 34% of children with perennial AR and 13% of those with seasonal AR developed asthma after a follow-up period of 8–11 years [3]. Conversely, almost 57.7% of children with asthma had required medications for rhinitis within the last year, and 68.8% had fi ndings consistent with AR in another study [4]. Consequently, two main guidelines considering the diagnosis and treatment of AR have recently been produced: Allergic Rhinitis and its Impact on Asthma (ARIA) [5], and the European Position Paper on Nasal Polyps and Rhinosinusitis (EPOS) [6]. Chronic idiopathic urticaria (CIU) is also a frustrating condition for patients, and has a negative impact on the quality of life of affected patients and limits daily activities. Characterized by hives and pruritus, CIU may result in sleep disturbances and social restrictions. The true incidence of CIU is unknown; however, it is believed to occur in 0.1–3% of the population. Antihistamines are the mainstay of therapy for CIU [7]. Histamine has a major role in the pathogenesis of allergic rhinitis and urticaria via the histamine H1 receptors. Nonsedating antihistamines are the principal fi rst-line therapy for AR and CIU according to the European Academy of Allergology and Clinical Immunology (EAACI) and ARIA guidelines [5,8]. Many antihistamines are currently available, which have shown effectiveness in the treatment of related symptoms. First-generation antihistamines, such as chlorphenyramine and diphenhydramine, are not recommended by any of the major therapeutic guidelines because they are highly lipophilic, substantially pass the blood–brain barrier and result in sedation, impaired cognitive functions, sleep disturbances and reduced quality of life. Newer antihistamines are associated with a better safety profi le, lower incidence of sedation and cardiovascular adverse effects, as well as higher potency, faster onset and longer duration of action. Desloratadine is a second-generation nonsedating antihistamine used currently in the treatment of AR and CIU. This review focuses Desloratadine is a second-generation nonsedating antihistamine currently used in the treatment of allergic rhinitis and chronic idiopathic urticaria. It is the major active metabolite of loratadine. The binding affi nity of desloratadine for H1 receptors is the highest among all antihistamines. Besides the effects of desloratadine on H1 receptors, it may also reduce the release of anti-infl ammatory cytokines and other mediators involved in the earlyand late-phase allergic response. Desloratadine is well-tolerated, and most adverse events reported are mild/moderate and experienced by a small proportion of the patients. Many large, randomized, double-blind, placebo-controlled trials have confi rmed that desloratadine is effective against symptoms of intermittent and persistent allergic rhinitis. Patients with chronic idiopathic urticaria also experience marked relief of symptoms upon treatment with desloratadine, since urticarial symptoms in chronic idiopathic urticaria are largely mediated by histamine.