Instalast Tablet contains Levocetirizine 5mg and Montelukast 10mg, combining an antihistamine and a leukotriene receptor antagonist to provide effective relief from allergic conditions. Levocetirizine, a third-generation non-sedating antihistamine, selectively inhibits peripheral H1 receptors, thereby reducing symptoms such as sneezing, nasal congestion, rhinorrhea, and itching associated with allergic rhinitis and chronic urticaria. Montelukast, a selective leukotriene receptor antagonist, blocks the action of leukotriene D4 on cysteinyl leukotriene receptors in the lungs and bronchial tubes, leading to decreased inflammation, bronchoconstriction, and mucus production. The synergistic effect of these two agents makes Instalast Tablet suitable for the management of seasonal and perennial allergic rhinitis, as well as asthma prophylaxis and treatment of chronic urticaria. It is generally well tolerated, with a low incidence of adverse effects such as headache, fatigue, and gastrointestinal disturbances. Instalast Tablet should be used under medical supervision, with dosage adjusted according to patient age and clinical response. It is contraindicated in patients with hypersensitivity to any component and should be used cautiously in individuals with hepatic or renal impairment. This combination therapy offers a convenient once-daily dosing regimen to improve patient compliance and quality of life.