Topic overview

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Controlled release (CR) delivers drug at a near-constant rate for a defined period; sustained release (SR) slows drug liberation to extend duration, though its release rate may decline over time. Both approaches can support adherence, reduce dosing frequency and peak–trough fluctuations, and may help minimize adverse drug reactions. Their performance depends on drug characteristics, formulation design, and physiological conditions. Approaches include polymer matrices, coated reservoir systems, osmotic pumps, ion-exchange resins, biodegradable systems, and multiparticulates. Release may occur through diffusion, dissolution, osmosis, ion exchange, swelling, or erosion. Mathematical models such as zero-order, first-order, Higuchi, and Korsmeyer–Peppas are used to interpret release kinetics. The lesson also considers candidate-drug traits, commonly used polymers, physiological influences, and evaluation and quality-control topics.