Enhanced Stability and Compatibility of Montelukast and Levocetirizine in a Fixed-Dose Combination Monolayer Tablet

1. Introduction

In recent decades, the prevalence of respiratory and allergic diseases, such as allergic rhinitis and asthma, has increased [1]. While not directly life-threatening, respiratory allergic diseases significantly deteriorate quality of life [2]. Two prominent types of these allergic diseases are asthma and rhinitis [3]. Asthma, a common chronic condition, induces persistent difficulty in breathing, coughing, and other respiratory symptoms [4]. Allergic rhinitis, which is characterized by inflammation of the nasal mucosa, results in symptoms such as nasal discharge and sneezing [5]. Although asthma and allergic rhinitis can occur independently, up to 40% of rhinitis patients may also have asthma, and as much as 80% of asthma patients may experience rhinitis, which indicates a high co-occurrence within the same patient population [6]. Therefore, integrated treatment of allergic rhinitis and asthma is recommended according to the Allergic Rhinitis and its Impact on Asthma (ARIA) guidelines, which advise combining antihistamines and leukotriene receptor antagonists [7,8]. Levocetirizine, a second-generation antihistamine, is frequently used to treat allergic rhinitis [9], while montelukast, a CysLT1 receptor antagonist, helps improve asthma symptoms by blocking the binding of leukotrienes to a receptor [10]. In patients with persistent allergic rhinitis, combination therapy with montelukast and levocetirizine is more effective than montelukast monotherapy [11]. Additionally, fixed-dose combination (FDC) therapy with montelukast and levocetirizine has proven its superiority through phase III clinical trials for treating allergic rhinitis in asthma patients [12,13]. Furthermore, in terms of safety, there is no difference between short-term administration (1–4 weeks) and long-term administration (3–6 months), thus making it an effective and safe drug for improving the symptoms of perennial allergic rhinitis with asthma, even after long-term use [14].