Advances in Controlled Drug Delivery Systems

Abstract

Controlled drug delivery systems are designed to regulate the amount of drug reaching the body over time rather than releasing the entire dose immediately. Their main purpose is to maintain drug exposure within a useful therapeutic range, reduce unnecessary fluctuations, decrease dosing frequency, and improve treatment convenience. This review summarizes the development and current principles of controlled drug delivery, beginning with conventional modified-release systems and extending to osmotic, transdermal, implantable, gastroretentive, stimuli-responsive, and nanocarrier-based platforms. The role of pharmacokinetic properties such as half-life, absorption, distribution, and therapeutic index is considered because these factors determine whether a drug is a suitable candidate for controlled release. Major release models, including zero-order, first-order, Higuchi, Hixson-Crowell, and Korsmeyer-Peppas approaches, are discussed as practical tools for interpreting release behaviour. The review also considers polymeric biomaterials, hydrogels, biodegradable polymers, liposomes, lipid nanoparticles, and microfluidic manufacturing. Recent directions include microneedles, three-dimensional printing, programmable dosage forms, stimuli-responsive carriers, and artificial-intelligence-assisted formulation. Although these technologies offer improved temporal and spatial control, translation is still limited by reproducibility, stability, dose dumping, toxicity, scale-up, sterilization, regulatory requirements, and the gap between laboratory and clinical performance. Future progress will depend on combining sound pharmacokinetic design with robust materials, manufacturing control, and patient-specific approaches.