Coating Techniques for Sustained Release Pellet Dosage Forms: Strategies for Achieving Zero-Order Release Kinetics

The pursuit of zero-order drug release has become a key objective in the design of sustained release (SR) oral dosage forms, aiming to maintain constant plasma drug levels and enhance therapeutic efficacy. Pellet-based multiparticulate systems offer significant advantages in controlled drug delivery, including uniform distribution in the gastrointestinal tract, reduced risk of dose dumping, and flexible formulation design. Central to achieving desired release profiles is the application of functional polymer coatings that regulate drug diffusion. This review comprehensively explores coating techniques for sustained release pellets, with a particular focus on strategies that enable zero-order kinetics. It covers the principles of pelletization, polymer selection, coating technologies, and formulation innovations. Special emphasis is placed on multi-layer coating designs, the use of pore-forming agents, and osmotically driven mechanisms. Recent advances such as nanocoating, 3D printing, and Quality by Design (QbD) approaches are also discussed. The review concludes with an overview of current challenges and future directions in achieving consistent, predictable, and patient-centric drug delivery through advanced coating technologies.