Monolithic Osmotic Tablets for Controlled Delivery of Antihypertensive Drug

An oral monolithic osmotically controlled delivery system for nifedipine using asymmetric membrane technology was developed and evaluated. Unlike conventional osmotic systems, which require laser drilling, this system releases the drug in a controlled manner from asymmetric membrane coated core tablets. Asymmetric membrane is formed by dry process with phase inversion technology process using cellulose acetate as the coating material. Higher water influx of this membrane aids in delivery of nifedipine, which is highly water insoluble with low osmotic pressure. The porous structure of the membrane was confirmed by scanning electron microscopy. Influence of different osmotic agents on drug release was evaluated. In vitro release studies showed that as concentration of osmotic agents was increased, the drug release was also enhanced. Drug release from the developed monolithic system was independent of external agitation and pH of dissolution media. Comparative in vitro release data was obtained using different types of coating membranes like controlled porosity membrane and dense coating membrane with mechanically drilled orifice. Osmotic pressure generated in the system was determined using freezing point osmometer. The osmotic pressure developed was found to be linearly proportional to time and concentration of osmotic agent.