Mucinex DM Max Strength 1200 Mg Guaifenesin & 60 Mg Dextromethorphan Hbr Extended-Release Bi-Layer Tablets Expectorant/Cough Suppressant, 14 ct: Maximum Strength Mucinex DM breaks up mucus and quiets wet and dry coughs. Mucinex DM is specially formulated in a bi-layer tablet. The immediate release layer goes to work fast while the extended release layer continues to work for 12 hours. Maximum Strength Mucinex DM has the maximum amount of medicine to fight chest congestion and wet and dry coughs for 12 hours. * Quiets wet and dry coughs * Thins and loosens mucus that causes chest congestion * Starts to work right away and lasts for 12 hours