Micro-suspension coating method: a new approach in formulation and development of controlled porosity osmotic pump systems.

The aim of this study was to design and evaluate diltiazem hydrochloride controlled porosity osmotic pump (CPOP) system employing a new coating technique named the micro suspension coating method. In this method the fast dissolving pore formers were suspended in polymeric coating solution as micronized particles. Cellulose acetate and dextrose were used as film former polymer and pore former, respectively. 4 comparative parameters i. e., D24h (cumulative release percent after 24 h), Devzero (mean percent deviation of drug release from zero order kinetic), tL (lag time of the drug release) and RSQzero were used to assess various formulations. The results showed a significant increase of D24h due to the decrease in the thickness of the semipermeable membrane (SPM) and increase of the sucrose concentration (P<0.05). An inverse relationship was seen between sucrose amounts and drug release lag times of the formulations. In addition, lag time was significantly reduced following addition of tween 80 to SPM formulation (P<0.05). Results of scanning electron microscopy studies exhibited formation of pores in the membrane from where the drug release occurred. Micro suspension coating method was found to be a novel and promising method to formulate CPOP system of diltiazem hydrochloride.