Hayrest-D Syrup is a combination pharmaceutical formulation containing Phenylephrine (5mg/5ml), Chlorpheniramine Maleate (2mg/5ml), and Dextromethorphan Hydrobromide (10mg/5ml). This syrup is indicated for the symptomatic relief of nasal congestion, allergic rhinitis, and cough associated with upper respiratory tract infections. Phenylephrine acts as a selective alpha-1 adrenergic receptor agonist, providing effective decongestion by vasoconstriction of nasal blood vessels, thereby reducing mucosal edema. Chlorpheniramine Maleate, a first-generation antihistamine, exerts antiallergic effects by competitively inhibiting histamine H1 receptors, alleviating symptoms such as sneezing, runny nose, and itching. Dextromethorphan Hydrobromide serves as a centrally acting antitussive agent that suppresses the cough reflex by acting on the medullary cough center without causing significant respiratory depression. Hayrest-D Syrup is suitable for adults and children above the age specified in the prescribing information and should be used under medical supervision, especially in patients with hypertension, glaucoma, or thyroid disorders. Common adverse effects may include drowsiness, dizziness, dry mouth, and gastrointestinal discomfort. Caution is advised when used concomitantly with monoamine oxidase inhibitors or other CNS depressants. This combination therapy offers comprehensive relief from multiple symptoms of respiratory tract infections, improving patient comfort and quality of life.