This book contains two parts. Part [A] deals with preparation, characterisation of polymer loaded simvatstain nanoparticles and its antihyperlipidemic activity. Part [B] of this chapter contains RP-HPLC method development and validation of simvastatin from bulk drug, tablet formulation and nanoparticles. In this study, simvastatin Np (SNp) formulations comprising SV were developed using different proportions of polymer. Here, we used nanoprecipitation method to prepare SV loaded nanoparticles. Other methods have also been accounted in previous years for SV Np and microparticles, however, no studies have been described for SV with ELD polymer. A few methods of antihypertensive drugs like lovastatin,satranidazole were also reported. Several attempts have been made to formulate sustained release dosage forms previously. Objective of our work is to prepare polymeric drug nanoparticles of SV to improve the solubility, dissolution rate and bioavailability by controlling the size of Nps. Also to develop RP-HPLC method for the assay of the nanoparticles of SV.