Mucinex Fast-Max adult severe congestion and cough caplets helps relieve severe congestion and cold symptoms with caplets that combine the mucus busting power of Mucinex and maximum strength medicines. It's a whole new day for relief in a brand new caplet from Mucinex. Mucinex Fast-Max Adult Severe Congestion and Cough Caplets contains Dextromethorphan HBr cough suppressant, Guaifenesin expectorant, and Phenylephrine HCl nasal decongestant. Use to control cough, relieve nasal and chest congestion, and thin and loosen mucus. Per 4 hour dose.