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Exefen (Pseudoephedrine Hydrochloride / Guaifenesin) - Description and Clinical Pharmacology


Rx Only


Each immediate-release tablet for oral administration contains:

Pseudoephedrine HCl    60 mg
Guaifenesin    400 mg

Inactive ingredients

Croscarmellose Sodium, Magnesium Stearate, Maltodextrin, Microcrystalline Cellulose, Polyvinylpyrrolidone, Silica and Stearic Acid.

Pseudoephedrine hydrochloride is an adrenergic (vasoconstrictor) which occurs as fine, white to off white crystals or powder, having a faint characteristic odor. It is very soluble in water, freely soluble in alcohol and sparingly soluble in chloroform. The chemical name is benzenemethanol, alpha - [1-(methylamino) ethyl]-, [S-(R*,R*)]-, hydrochloride. The structural formula is:

Guaifenesin is an expectorant and occurs as a white to slightly gray, crystalline powder, having a bitter taste. It may have a slight characteristic odor. It is soluble in water, in alcohol, in chloroform, in glycerin and in propylene glycol. The chemical name is: 1,2 propanediol, 3-(2-methoxyphenoxy)-. Chemically, Guaifenesin is 1,2-Propanediol, 3-(2-methoxyphenoxy)-,(+) and has the following structural formula:



Pseudoephedrine acts as an indirect sympathomimetic agent by stimulating sympathetic (adrenergic) nerve endings to release norepinephrine. Norepinephrine in turn stimulates alpha and beta receptors throughout the body. The action of pseudoephedrine is apparently more specific for the blood vessels of the upper respiratory tract and less specific for the blood vessels of the systemic circulation.The vasoconstriction elicited at these sites results in the shrinkage of swollen tissues in the sinuses and nasal passages. Pseudoephedrine is rapidly and almost completely absorbed from the gastrointestinal tract. Considerable variation in half-life has been observed (from about 4 1/2 to 10 hours), which is attributed to individual differences in absorption and excretion. Excretion rates are also altered by urine pH, increasing with acidification and decreasing with alkalinization. As a result, mean half-life falls to about 4 hours at pH 5 and increases to 12 to 13 hours at pH 8.

After administration of a 60 mg tablet, 87 to 96% of the Pseudoephedrine is cleared from the body within 24 hours. The drug is distributed to body tissues and fluids, including fetal tissue, breast milk, and the central nervous system (CNS). About 55 to 75% of an administered dose is excreted unchanged in the urine; the remainder is apparently metabolized in the liver to inactive compounds by Ndemethylation, parahydroxylation and oxidative deamination.


Guaifenesin is an expectorant which increases respiratory tract fluid secretions and helps to loosen phlegm and bronchial secretions. By reducing the viscosity of secretions, Guaifenesin increases the efficiency of the cough reflex and of ciliary action in removing accumulated secretions from the trachea and bronchi. Guaifenesin is readily absorbed from the gastrointestinal tract and is readily 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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