Compare to the active ingredients of Mucinex DM. When you need powerful multi-symptom relief, trust Mucus DM. This over-the- counter (OTC) medicine pairs a cough suppressant with an expectorant to give you 12 hours of mucus relief. The extended-release tablets contain guaifenesin 600 mg and dextromethorphan hydrobromide 30 mg. Each dose of this mucus medication helps loosen phlegm (mucus) to make coughs more productive, and also temporarily relieves cough due to minor throat and bronchial irritation as may occur with the common cold or inhaled irritants. This medicine also relieves the intensity of coughing and the impulse to cough to help you sleep. Gluten free. For adults and children 12 years and older.