Guaifenesin
Guaifenesin, also known as glyceryl guaiacolate, is an over-the-counter medicine sold for chest and cough relief (brand names include Mucinex and others). It is an expectorant, meaning it helps thin and loosen mucus in the airways so you can cough it up more easily.
How it works: Guaifenesin is thought to irritate the stomach slightly, triggering a reflex that increases the volume and thinning of mucus in the airways. This helps mucus move toward the throat and out of the lungs. Some studies suggest it might also have a central effect on coughing, but evidence for clear, consistent benefit is mixed.
How you take it: It is taken by mouth in forms such as tablets, capsules, extended-release tablets, dissolving granules, or syrup. It is commonly used alone or in combination with other medicines, like the cough suppressant dextromethorphan or with pain relievers and decongestants.
Effectiveness and safety: Research on its effectiveness for acute cough is mixed—some trials show benefit, others do not. Guaifenesin is generally well tolerated. Side effects can include dizziness, drowsiness, nausea, vomiting, headache, or a skin rash; allergic reactions are rare. Its safety in pregnancy isn’t well studied, so talk with a clinician if you’re pregnant or planning to become pregnant.
History and usage: Guaifenesin has been used since the 1930s and is available as a generic, widely sold over the counter. It is also sometimes used in combination products with other cough, cold, or pain-relief medicines. In veterinary settings, it has been used as a muscle relaxant in large animals, such as horses.
This page was last edited on 2 February 2026, at 05:10 (CET).