Hydrogels in Pharmaceutical Formulation: Properties, formulation strategies, and drug delivery applications.
OBJECTIVES This review aims to provide a systematic overview of hydrogel systems as pharmaceutical excipients for drug delivery. It focuses on their classification, formulation strategies, physicochemical properties, and applicability across different routes of administration. SIGNIFICANCE Hydrogels have progressed into multifunctional excipients capable of modulating drug release, enhancing residence time, and improving patient compliance. This review consolidates formulation-oriented knowledge while addressing translational, manufacturing, and regulatory considerations. KEY FINDINGS Hydrogels are classified based on source, polymer type, network charge, physical form, and cross-linking methods. Key excipient properties-including swelling, porosity, mechanical strength, biodegradability, and environmental responsiveness-govern performance. Diverse fabrication techniques support tailored design for oral, topical, transdermal, ocular, rectal, and injectable delivery. Challenges such as scalability and reproducibility persist, while stimuli-responsive and composite hydrogels offer promising solutions. CONCLUSION This review highlights a formulation-driven framework for the rational design and clinical translation of hydrogel-based pharmaceutical excipients in advanced drug delivery systems.