Formulation and Evaluation of a Transdermal Drug Delivery System of Antihyperlipidemic Drug Simvastatin

The present study was aimed at developing Simvastatin loaded transdermal patch to prevent drawbacks associated with oral delivery of Simvastatin. Simvastatin is a BCS class II drug having poor aqueous solubility and good permeability. A transdermal patch of simvastatin was developed using various polymers and their combination like Eudragit RL 100, HPMC K4M, PVP K30 & Ethyl Cellulose. Polymer combination HPMC K4M & PVP K30 exhibited good film forming properties. Propylene glycol, oleic acid and glycerol were used as plasticizers to improve film-forming properties. Among these, propylene glycol exhibited excellent result but penetration was found to be less. Thus, penetration enhancers such as oleic acid, DMSO, PEG 200 were used to enhance permeability, of which DMSO was found to be excellent. A 22 factorial design was implemented using design expert software. The formulation was optimized on basis of 2 parameters percent cumulative release and percent drug content.  3D surface graph was plotted for the design. Grid survey indicated P1 batch (which contains HPMC K4M & PVP K30 as a polymer, DMSO as penetration enhancer & PEG as a plasticizer) is the optimized batch as it showed good drug content and in-vitro drug release. The drug release kinetics of transdermal patch of simvastatin was best expressed by Higuchi model of drug release.