Controlled release

Microspheres are multiparticulate drug delivery systems which are prepared to obtain prolonged or controlled drug delivery to improve bioavailability, stability and to target the drug to specific site at a predetermined rate. They are made from polymeric waxy or other protective materials such as natural, semi synthetic and synthetic polymers. Microspheres are characteristically free flowing powders having particle size ranging from 1-1000 μm consisting of proteins or synthetic polymers. The range of techniques for the preparation of microspheres provides multiple options to control as drug administration aspects and to enhance the therapeutic efficacy of a given the drug. These delivery systems offer numerous advantages compared to conventional dosage forms, which include improved efficacy, reduced toxicity, improved patient compliance and convenience. Such systems often use macromolecules as carriers for the drugs. The present review highlights various types of microspheres, different methods of preparation, its applications and also various parameters to evaluate their efficiency. Microspheres are various types like Bioadhesive microspheres, Magnetic microspheres, Floating microspheres, Radioactive microspheres, Polymeric microspheres, Biodegradable polymeric microspheres, Synthetic polymeric microspheres and are prepared by methods like Spray Drying, Solvent Evaporation, Single emulsion technique, Double emulsion technique, Phase separation coacervation technique, Spray drying and spray congealing, Solvent extraction, Quassi emulsion solvent diffusion. Microspheres have wide range of applications because of controlled and sustained release.

The aim of present study was to design and evaluate push pull osmotic pump-based drug delivery system for controlled release of Isoxsuprine hydrochloride for peripheral and cerebral vasodilation. Core tablets were prepared by direct Compression method. Effects of different variables like amount of osmogen, orifice size, coating thickness and dissolution media were studied on release profile. It observed that the combination of PEO 100000 and PEO 300000 give the desired drug release. On increasing the amount of osmogen, the release of drug was found to be increased. On comparison of f2 value no significant effect of pH of dissolution medium, agitation rate was observed but it was observed that the coating thickness decrease it shows the faster drug release and increase in orifice size also increases the drug release.  It was concluded that the osmotic pump tablets could provide more prolonged and controlled release that may result in an improved therapeutic efficacy and patient compliance.

Bilayer tablet is new era for the successful development of controlled release formulation and also provide a successful key for other drug delivery system. Bilayer tablet is made up of two layers in which one is immediate layer for initial dose and second layer is sustained layer for maintenance dose. Thus, bilayer tablet is useful for sequential release of two drugs in combination and is applicable for improved patient compliance and mainly for reduced toxicity. It is useful for both single and multiple dose therapy. The present article gives an idea about an introduction of bilayer tablet, various tablet presses, manufacturing process, GMP and quality requirements, and challenges in bilayer tablet and recent approach in bilayer tablet development.