Maximum Strength Mucinex extended-release tablets break up the mucus that causes chest congestion, providing you with fast-acting and long-lasting relief. With 12 hours of relief from chest congestion, you can make it through a workday without congestion getting in your way. Only Mucinex has an extended release bi-layer tablet to deliver maximum-strength congestion medicine. The first layer is absorbed quickly by your body for fast-acting relief. The other layer dissolves slowly to continue relieving your chest congestion for 12 hours. Relieves chest congestion Thins and loosens mucus that causes chest congestion Starts to work right away and lasts for 12 hours Extended-release bi-layer tablet Mucinex is the #1 doctor recommended OTC expectorant among Internists, General Practitioners and Family Practitioners.