ABSTRCT Objective Microemulsions have been widely studied to enhance the bioavailability of the poorly soluble drugs. They have very low surface tension and small droplet size which results in high absorption and permeation. Interest in these versatile carriers is increasing and their applications have been diversified to various administration routes in addition to the conventional oral route. This can be attributed to their unique solublization properties and thermodynamic stability which has

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... drawn attention for their use as novel vehicles for drug delivery Method Lovastatin is systemic lipid lowering drug belonging to statins and is used for lowering blood cholesterol. Like all statins, lovastatin works by inhibiting 3-hydroxy-3-methylglutaryl-coenzyme A (HMG-CoA reductase). Pseudoternary phase diagram was constructed to determine the ME existing zone. Optimised ME was evaluated for its transparency, droplet size, zeta potential, viscosity, conductivity, percentage assay, and phase separation study. Solubilisation capacity of the ME system was also determined. An accelerated stability study of optimised ME was carried out to check the stability of the formulation. The prepared ME was compared with the pure drug solution and commercially available lovastatin tablet for in vitro drug release. Comparative oral absorption of lovastatin from the ME and suspension of the commercially available lovastatin was investigated through an in vivo study in a rat model. Result Hence microemulsion produced by water titration method showed good particle size (95nm). Refractive index and % transmittance showed good isotropic formulation. In vitro drug release studies revealed overall increase in release from micro-emulsion compared to lovastatin marketed tablet formulation microemulsion showed 76.72% release and marketed formulation showed 52.3% release. There is no physical interaction between drug and excipients, hence collectively it shows microemulsion is promising drug delivery system. INTRODUCTION Microemulsions are clear transparent, thermodynamically stable dispersion of oil and water, stabilized by interfacial film of surfactant frequently in combination with a co-surfactant. Recently there has been a considerable interest for microemulsion formulation, for the delivery of hydrophilic as well as liphophlic drug as drug carriers because of its improved drug solubilisation capacity, long shelf life, ease of preparation and improvement of bioavailability. In this present review, we have discuss biopharmaceutical aspects, advantages, disadvantage, theories, formulations, marketed lipid based formulations, factors affecting formulation and phase behaviour, preparations, characterization and pharmaceutical application of microemulsions 32. Microemulsions have been widely studied to enhance the bioavailability of the poorly soluble drugs. They offer a cost effective approach in such cases. Microemulsions have very low surface tension and small droplet size which results in high absorption and permeation. Interest in these versatile carriers is increasing and their applications have been diversified to various administration routes in addition to the conventional oral route. This can be attributed to their unique solublization properties and thermodynamic stability which has drawn attention for their use as novel vehicles for drug delivery. The results obtained have been indeed very promising. In recent past, microemulsion formulation of a poorly soluble immunosuppressant was marketed as a soft capsule which contains a mixture of drug dissolved in oil and surfactant. It converts into an oil-in-water (o/w) microemulsion in situ in an aqueous environment in the stomach and the small intestine. Microemulsion formulation made the bioavailability and plasma concentration profiles of the drug more reproducible which is clinically important in the case of drugs showing serious adverse effects. This is a significant step forward in the Sujit Arun Desai et al.