Dextromethorphan, a centrally-acting antitussive agent, depresses the medullary cough center through sigma receptor stimulation, resulting to decreased sensitivity of cough receptors and interruption of cough impulse transmission.
Pseudoephedrine is both an α-and β-adrenergic receptor agonist. It causes vasoconstriction via direct stimulation of α-adrenergic receptors of the respiratory mucosa. It also directly stimulates β-adrenergic receptors causing bronchial relaxation, increased heart rate and contractility.
Triprolidine binds to the histamine H1 receptor. This block the action of endogenous histamine, which subsequently leads to temporary relief of the negative symptoms brought on by histamine.