An Overview of Conventional, Controlled, Targeted and Nanotechnology-Based Approaches in Drug Delivery System

Drug delivery systems (DDS) are formulations or technological platforms designed to deliver active pharmaceutical ingredients at an appropriate rate, to an appropriate site, and for a predetermined duration in order to improve therapeutic efficacy, safety, and patient compliance. Conventional dosage forms remain widely used, but they may provide limited control over the rate, duration, and site of drug release. This review provides an overview of conventional and advanced drug delivery approaches, including sustained and controlled release systems, transdermal delivery, mucoadhesive systems, targeted delivery, colon-targeted delivery, pulmonary delivery, and nanocarrierbased platforms. The review discusses the principles, major advantages, limitations, and applications of these systems and highlights the role of modern polymers, lipids, nanocarriers, and responsive biomaterials. The manuscript also considers challenges associated with formulation design, biological variability, safety, characterization, and clinical translation. Overall, advances in drug delivery technology have expanded the ability to control drug release and improve therapeutic outcomes, although careful formulation design and scientific evaluation remain essential.