Fight bothersome congestion in the chest by taking Mucinex Expectorant Extended-Release Bi-Layer Tablets. It helps relieve chest congestion by thinning and loosening mucus that causes congestion and lasts for 12 hours. It comes in an extended-release bi-layer tablet that continues to work for hours after your initial intake. The extended-release layer provides symptomatic relief for up to 12 hours - all day or night.