Multiple Unit Asymmetric Membrane Capsule: A Means for Delivery of Highly Water Soluble Drug

Abstract

A multiple unit, non-disintegrating asymmetric polymeric capsular system was used to deliver highly water-soluble drug in a controlled manner. A highly water-soluble drug, metformin hydrochloride (MHCl), was selected as a model drug to demonstrate how the controlled release could be generated in vitro by changes in the core as well as the coating formulation. Formation of asymmetric capsule wall membrane involved wet phase inversion process, in which the asymmetric membrane (AM) was precipitated on glass mold pins by dipping the mold pins into a coating solution containing the good and bad solvents for the polymer followed by quenching in an aqueous quench bath. The study optimized by 23 factorial design evaluates the influence of coating formulation namely concentration of ethylcellulose and pore former (glycerol) and core component namely controlled release potassium chloride crystals. Scanning Electron Microscopy (SEM) showed the presence of outer dense non porous region and inner, thick, porous region for the prepared AM. Statistical test were applied at P > 0.05 on all the formulations undergoing in vitro release studies. Results showed the solubility of MHCl to have been modulated (reduced) over an extended period of time with pH independent, and osmotic pressure dependant drug release. The release kinetics was found to be zero order.