Pseudoephedrine is a decongestant as well as a bronchodilator for the upper respiratory tract, which gives symptomatic relief of nasal congestion. Pseudoephedrine is both an ?-and ?-adrenergic receptor agonist. It causes vasoconstriction via direct stimulation of ?-adrenergic receptors of the respiratory mucosa. It also directly stimulates ?-adrenergic receptors causing bronchial relaxation, increased heart rate and contractility.
Like ephedrine, pseudoephedrine releasing norepinephrine from its storage sites, an indirect effect. This is its main and direct mechanism of action. The displaced noradrenaline is released into the neuronal synapse where it is free to activate the postsynaptic adrenergic receptors.
Guaifenesin reduces the viscosity of tenacious sputum and is used as an expectorant. It increases the hydration of respiratory tract, thereby increasing the volume and reducing the viscosity of bronchial secretions.
Triprolidine is an antihistamine; it is used for the symptomatic relief of hypersensitivity reactions including rhinitis, conjunctivitis and urticaria.