Pseudoephedrine hydrochloride is an orally indirect acting sympathomimetic amine and exerts a decongestant action on the nasal mucosa. It does this by vasoconstriction which results in reduction of tissue hyperemia, edema, nasal congestion, and an increase in nasal airway patency. The vasoconstriction action of pseudoephedrine is similar to that of ephedrine. In the usual dose it has minimal vasopressor effects. Pseudoephedrine is rapidly and almost completely absorbed from the gastrointestinal tract. It has a plasma half-life of 6 to 8 hours. Alkaline urine is associated with slower elimination of the drug. The drug is distributed to body tissues and fluids, including the central nervous system (CNS). Approximately 50% to 75% of the administered dose is excreted unchanged in the urine; the remainder is apparently metabolized in the liver to inactive compounds by N-demethylation, parahydroxylation and oxidative deamination.

Guaifenesin is an expectorant which increases respiratory tract fluid secretions and helps loosen phlegm and bronchial secretions. By reducing the viscosity of secretions, guaifenesin increases the efficiency of the mucociliary mechanism in removing accumulated secretions from the upper and lower airway. Guaifenesin is readily absorbed from the gastrointestinal tract and is rapidly metabolized and excreted in the urine. Guaifenesin has a plasma half-life of one hour. The major urinary metabolite is beta-(2-methoxyphenoxy) lactic acid.

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