Oral sustained release expandable dosage forms: innovations, challenges, and future directions.

Oral sustained-release dosage forms have gained considerable attention for their ability to enhance therapeutic outcomes and improve patient compliance. Among these, expandable drug delivery systems represent a significant innovation, offering extended gastric retention and controlled drug release through size-based retention strategies. These systems expand in the stomach after administration, delaying gastric emptying and enabling prolonged drug action. This review presents a consolidated overview of key expandable mechanisms-such as swelling, unfolding, floating, and mucoadhesion-along with a detailed discussion on formulation strategies, polymeric materials, and in vivo behavior. Special emphasis is placed on recent advancements in smart polymers, 3D printing, and novel fabrication techniques. The review also explores clinical applications, manufacturing challenges, safety concerns, and future research directions. By integrating scientific, technical, and translational insights, this paper aims to highlight the potential of expandable dosage forms in advancing oral drug delivery technologies.