Osmotically Regulated Two-Compartment Asymmetric Membrane Capsules for Simultaneous Controlled Release of Anti-Hypertensive Drugs

In the present study, asymmetric membrane capsules (AMCs) with two com-partments were successfully developed for simultaneous delivery of two poorly water-soluble drugs, Atenolol and Amlodipine Besylate, by using solubility modulation approach. Scanning electron microscopy (SEM) before dissolution showed presence of outer dense region and inner porous region for the prepared asymmetric membrane and the pore size increased after dissolution for both outer and inner layer. Diffuse reflectance spectroscopy (DRS) showed no incompatibility between the drug(s) and the excipients used in the study. The developed system was able to control the release of ATN and AMB by increasing the solubility through buffering agents of different strengths (0.25N to 1.0N). As the level of buffering agent was increased, the solubility of drugs also increased inside the asymmetric membrane capsule. The developed system was independent of the agitation intensity of the dissolution fluid but was dependent on the polymer diffusibility and osmotic pressure of the media, which clearly stated that osmotic pumping was the primary mechanism of drug(s) release from AMCs. The results of in-vitro demonstration of effect of membrane thickness on dissolution fluid entering AMCs showed that as the membrane thickness increased the volume of dissolution fluid entering into AMC decreased. The release kinetic studies of different formulations of AMCs showed that formulation code six, which consists of the highest amount of osmotic agents and optimum amount of buffering agents, was the best formulation, and it followed zero order release kinetics (r²=0.9990 for ATN and r²=0.9988 for AMB).