Solvent evaporation technique is widely employed to obtain the controlled release of drug. In this method, the drug and polymer are dissolved in an organic phase (usually methylene chloride) and dispersed in an excess amount of aqueous continuous phase, with the aid of an agitator to form an emulsion [Figure 2]. Depending upon the hydrophilicity or the hydrophobicity of drugs, different methods are used to prepare microspheres by solvent evaporation technique [Table 1]. The oil-in-water method is frequently utilized for insoluble or poorly water-soluble drugs, whereas for hydrophilic drugs, this method is inappropriate due to dissolution and extensive loss of drug. Hence, for incorporation of hydrophilic drugs water in oil in water double emulsion method, oil in water co-solvent method and oil in oil non-aqueous solvent evaporation method can be employed. [20]