This book reveals the concept of mixed solvency, which explains that all substances whether liquids, gases or solids possess solubilizing power .Till now this concept have been utilized extensively in the field of pharmaceutical analysis and formulation. Furosemide is a widely used loop diuretic indicated for the treatment of different pathological conditions such as congestive heart failure, hepatic cirrhosis, and chronic renal failure. The objective of present work is to develop gastroretentive controlled release microspheres of furosemide using emulsification solvent evaporation method by using mixed solvency concept with the aim to make ethyl acetate a strong solvent for emulsification solvent evaporation process and to preclude the use of toxic organic solvents since ethyl acetate is safer (class 3 organic solvent) than those generally employed for microsphere production i.e. methylene chloride (class 2 organic solvent). This book provides detailed knowledge of mixed solvency concept, microspheres preparation technique and optimization methodology.