Guaifenesin/Pseudoephedrine

**Semantic type:** Pharmacologic Substance

**Definition:** A combination preparation containing guaifenesin and the indirect-acting sympathicomimetic agent pseudoephedrine with expectorant and decongestant activities, respectively. Guaifenesin works by drawing water into respiratory tracts, by which reducing adhesiveness and surface tension of mucus as well as increasing hydration of mucus, thereby reducing the viscosity of mucus and making cough more productive. Pseudoephedrine displaces norepinephrine from storage vesicles in presynaptic neurons, thereby releasing norepinephrine into the neuronal synapses where it stimulates primarily alpha-adrenergic receptors in the nasal mucosa, thereby producing vasoconstriction, reduces swelling of nasal mucous membranes and decreasing nasal and sinus congestion.