The Food and Drug Administration (FDA or Agency) is announcing the availability of a draft guidance for industry entitled “Safety Labeling Changes—Implementation of Section 505(o)(4) of the Federal Food, Drug, and Cosmetic Act." This draft guidance provides information on the implementation of the statutory provision that authorizes FDA to require application holders for certain drug and biological products to make labeling changes based on new safety information that becomes available after approval of the drug that FDA determines should be included in the labeling of the drug. This guidance is being updated and reissued in draft to, among other things, include the addition of information related to Congress’ 2018 changes to the definition of adverse drug experience regarding reduced effectiveness and make other changes to reflect current Agency processes and procedures regarding safety labeling changes. This draft guidance revises and, when finalized, will replace the guidance for industry entitled "Safety Labeling Changes—Implementation of Section 505(o)(4) of the FD&C Act" issued in July 2013.