REVIEW ON SUSTAINED RELEASE BLEND MICROSPHERES
Shivam Gaur, Satkar Prasad
ABSTRACT
Sustained release drug delivery systems have emerged as an advanced approach in pharmaceutical technology to maintain therapeutic drug concentrations over an extended period, thereby enhancing efficacy and reducing dosing frequency. Among various delivery systems, microspheres have gained considerable attention due to their ability to encapsulate drugs and provide controlled release. The present study focuses on the formulation and evaluation of sustained release blend microspheres using a combination of polymers to overcome the limitations of single-polymer systems. Polymer blending plays an important role in modulating drug release by combining hydrophilic and hydrophobic polymers, which provide a synergistic effect in controlling drug diffusion, swelling behavior, and matrix integrity. Various preparation methods such as solvent evaporation, spray drying, coacervation, and ionic gelation are employed to develop microspheres with desired characteristics. Among these, the solvent evaporation method is widely used due to its simplicity and reproducibility. The performance of microspheres is influenced by formulation and process variables such as drug-to-polymer ratio, type and concentration of polymers, solvent system, stirring speed, and emulsifier concentration. These factors significantly affect particle size, entrapment efficiency, surface morphology, and drug release kinetics. Drug release from microspheres typically follows mechanisms such as diffusion, swelling, erosion, and polymer degradation, and can be analyzed using kinetic models including zero-order, first-order, Higuchi, and Korsmeyer–Peppas models. Evaluation parameters such as particle size analysis, scanning electron microscopy, drug entrapment efficiency, percentage yield, buoyancy studies, in-vitro drug release, and zeta potential are essential to assess the quality and performance of microspheres. Sustained release blend microspheres offer numerous advantages including improved bioavailability, reduced side effects, enhanced patient compliance, and protection of drugs from degradation. Despite certain challenges such as scale-up difficulties and variability in particle size, advancements in polymer science and formulation techniques continue to improve the efficiency and applicability of microsphere-based drug delivery systems.
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