STUDIES ON EFFICIENT DRUG DELIVERY THROUGH CONTROLLED POROSITY OSMOTIC PUMPS
In the last three decades, there have been considerable adv ancements in drug delivery systems, which are targeted to overcome the limitations of conventional drug delivery systems. These systems exhibit controlled and sustained pattern of drug release at the required site of action in effective concentration to give effective therapeutic action and predictable plasma concentrations, thereby reducing the dose, dosage frequency, toxic adverse effects and provide reduction of blood level fluctuations, enhanced patient compliance and minimization of drug accumulation. These characteristics can be achieved by using a well- known phenomenon called osmosis which can provide both delayed and pulsatile drug delivery. Of all the osmotic pumps developed till date, controlled porosity osmotic pumps have proved to possess immense potential to exhibit these advantages establishing it as one of the most promising and reliable oral drug delivery systems in the recent times. Th is system comprises of core tablets consisting of a drug and osmogen along with other suitable excipients fu rther coated by a semipermeable membrane containing a polymer, plasticizer and water soluble pore forming agents. When these systems come in contact with the physiological aqueous environment, pore forming components are leached out, thereby allowing the osmogen in the core to swell pushing the drug out in a controlled pattern. Drug delivery follows zero order kinetics as the system is independent of different physiological factors within the gut lumen like pH and agitation. Further, the release pat tern can be predicted easily from the known properties on account of the drug and other components of the dosage form like type and concentration of osmogen, pore forming agents, coating thickness, burst strength etc. This system is commonly used in the treatment of chronic diseases where a prolonged duration of controlled release is desired. In the present review, controlled porosity osmotic pump is discussed in detail