Mucinex is an expectorant medication containing 600 mg of guaifenesin in extended-release bi-layer tablets. Each pack contains 20 tablets designed to provide 12-hour relief from chest congestion by thinning and loosening mucus. The active ingredient guaifenesin helps thin and loosen mucus in the airways, making it easier to clear congestion and breathe. The bi-layer tablet technology provides extended release of the medication over 12 hours for long-lasting symptom relief. This medication is used to help relieve chest congestion and mucus buildup associated with colds, bronchitis, and other respiratory conditions.