Asymmetric membrane in membrane capsules: A means for achieving delayed and osmotic flow of cefadroxil

In the present study, both disintegrating and non-disintegrating polymeric capsular system in achieving delayed as well as improved osmotic flow for the model drug cefadroxil was developed. Asymmetric membrane in membrane capsule (AMMC) was prepared on a glass mold pin via phase inversion process in two steps. Step 1 included formation of a non-disintegrating, asymmetric membrane capsule (AMC) and step 2 involved formation of a pH sensitive, disintegrating, asymmetric membrane (AM) formed over the non-disintegrating membrane. The effects of different formulation variables were studied namely, level of osmogen, membrane thickness, and level of pore former. Effects of varying osmotic pressure, agitational intensity and intentional defect in the inner membrane on drug release were also studied. Membrane characterization by scanning electron microscopy showed dense regions with less pores on the outer surface of the disintegrating membrane and porous regions on the inner surface of the non-disintegrating asymmetric membrane. In vitro release studies for all the prepared formulations were done (n = 6). The drug release was independent of pH, agitational intensity and intentional defect on the membrane but dependent on the osmotic pressure of the dissolution medium. The release kinetics followed the zero order and the mechanism of release was Fickian diffusion.