Development and Optimization of Controlled Porosity Osmotic Tablets of Lamotrigine Solid Dispersion

Background: The purpose of this study was to investigate the application of a controlled porosity osmotic tablet (CPOT) utilizing solid dispersion (SD) of poorly soluble drug. The patents on Cyclobenzaprine HCl (US4968507 A) and Venlafaxine salts (EP 2085078 A1) helped in the selection of drug and polymers. Method: The SDs having different ratio of drug to carrier (PVP K 30) were prepared by kneading method and optimized. Effect of three independent variables, total amount of osmogen (mannitol& potassium chloride), total amount of polymer (polyethylene oxide WSR 301, hydroxy propyl methyl cellulose K100 M) and polymer1: polymer 2 ratio were investigated using Box Behnken design. Core and coated tablets were evaluated for various parameters. In-vitro drug release profiles of CPOT tablets were compared with reference product Diffcore tablet, Lamictal XR (GlaxoSmith Kline Inc., USA). Results: All formulations showed acceptable parameters. Drug release from CPOT was determined as complete, zero order and pH-independent within the physiological pH range of the GI tract. Drug release was directly proportional to initial level of polymers and osmogens. Conclusion: The present results confirmed that prepared LTG SD serves as solubility modulator. Further, CPOT of LTG based on SD proved to be successful in delivering the drug in a controlled manner ensuring the once daily dosing for the treatment of convulsive disorders.