Parenteral drug delivery utilizing surface-eroding materials

INTRODUCTION: Long-acting parenteral drug delivery systems can improve therapeutic outcomes and patient adherence by achieving more consistent drug levels and reducing dosing frequency. However, many existing platforms release drugs at rates that are difficult to predict a priori and often require empirical characterization. Diffusion- and bulk degradation-based systems often exhibit burst release, nonlinear kinetics, and incomplete drug release, and can reduce encapsulated therapeutic bioactivity. Surface-eroding biomaterials offer an alternative strategy by confining degradation primarily to the material surface, enabling predictable, geometry-dependent release profiles, including the potential for zero-order drug delivery. AREAS COVERED: This review summarizes biodegradable materials exhibiting surface-eroding behavior, methods for distinguishing surface erosion from bulk degradation, and the application of surface-eroding materials in parenteral drug delivery. Literature published between 1985 and 2026 was identified through searches of PubMed, Google Scholar, and Consensus using terms related to surface erosion, polymer degradation, and controlled drug delivery, supplemented by reference-list screening and citation tracking. EXPERT OPINION: Surface-eroding materials offer opportunities for precise controlled drug release, yet translation remains limited by challenges in characterization, stability, and device manufacturing. Standardizing approaches for evaluating degradation mechanisms and advances in microscale device fabrication will be critical to defining their clinical role in parenteral drug delivery.