Ingredients in Robitussin Cough & Congestion

Robitussin is a North American brand-name cough syrup currently produced by the pharmaceutical company, Pfizer. The active ingredients in Robitussin DM are dextromethorphan HBr, a cough suppressant approved by the U.S. Food and Drug Adminstration in 1982, and guaifenesin, a mucus expectorant approved in 2002, according to According to the product website, this over-the-counter oral medication is cherry-flavored, offered in 100 or 250 mL bottles, and used to relieve coughs caused by colds and bronchitis. In addition to the two active ingredients, Robitussin DM also contains many inactive ingredients.

The active ingredients in Robitussin DM are dextromethorphan and guaifenesin. Credit: szefei/iStock/Getty Images

Dextromethorphan HBr

According to, dextromethorphan is classed as an analgesic and anti-trussive agent used to relieve coughs due to colds/bronchitis, but not chronic coughs that occur with smoking, asthma or emphysema. Dextromethorphan relieves cough by suppressing the cough reflex in the brain, according to One tablespoon of Robitussin DM is equivalent to 10 mg of dextromethorphan.


According to, guaifenesin belongs to a class of drugs known as expectorants. It works by thinning and loosening mucus in the airways, clearing congestion and lubricating the lungs, thereby making it easier to breathe. One tablespoon of Robitussin DM is equivalent to 100 mg of guaifenesin.

Binding Agents

According to, Robitussin DM contains three ingredients that can generally be called binders: propylene glycol, sucralose and high-fructose corn syrup. Binders keep all the ingredients intact. Binders are usually sugars, cellulose or modified cellulose, notes the "Dictionary of Pharmaceutical Medicine."

Thickening Agents

Robitussin DM contains glycerin, which according to the "Dictionary of Pharmaceutical Medicine," serves as a thickening agent, a humectant and a solvent. High-fructose corn syrup can also act as a thickener by increasing the viscosity of a liquid.

Preserving Agents

Another ingredient in Robitussin DM is sodium benzoate, which acts as a preservative because it has the ability to retard mold, yeast and some bacteria, according to the "Dictionary of Pharmaceutical Medicine." Anhydrous citric acid is another ingredient which functions as a natural preservative, as does sodium citrate, which is a salt-form antiseptic. Glycerin may also help preserve foods and liquids.

Color/Flavor Agents

Robitussin DM cough syrup is offered as cherry flavored, which is labeled as “flavoring” within the ingredients. The high-fructose corn syrup, sucralose and glycerin add to the syrup’s sweetness, according to the "Dictionary of Pharmaceutical Medicine." For coloring, Robitussin DM contains FD & C Red No. 40 and FD & C Yellow No. 6 dyes. The final ingredient is purified water, which makes up the vast majority of the syrup's content.

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