The main objective of pharmatherapeutics is to attainment of an effective drug concentration at the intended site of action for the sufficient period of time to elicit the response. The parenteral drug formulation mainly concern the methods to improve the solubility of the drug administered in a small volume and depot drug delivery system such as: micro- and nanoparticles, microemulsions, submicron emulsions and implants to achieve the desired therapeutic effect and to reduce the dosing intervals. In the area of parenteral drug delivery, controlled release of drug can be achieved by the use of biodegradable in situ formed systems.