This document provides an overview of Scale-Up and Post-Approval Changes (SUPAC) guidelines. It defines SUPAC and the scientific rationale for the guidelines, which aim to expedite post-approval changes while ensuring safety and effectiveness. The FDA has issued SUPAC guidelines for immediate-release, modified-release, and semi-solid dosage forms. These guidelines provide recommendations for post-approval changes to components/composition, manufacturing sites, batch size (scale-up), and manufacturing processes/equipment. They define three levels of changes and specify the tests, documentation, and required filings for each level. The document reviews the SUPAC guidelines sections in detail and discusses limitations of the current guidelines.