The development of oral controlled release system has been a challenge to formulation scientist due to their inability to restrain and localize the system at targeted areas of the gastrointestinal tract. Various physical and chemical approaches have been applied to produce a well characterized dosage form that controls drug input into the body within the specifications of the desired release profile. This is generally accomplished by attempting to obtain “zero-order” release from the dosage form, i.e., the rate of drug release is independent of the drug concentration. Controlled porosity osmotic pump tablet; which is an extension of elementary osmotic tablet, utilizes the principle of osmotic pressure for the delivery of drugs and avoids the expensive laser drilling for creation of delivery orifice on the tablet coat. They do not have any aperture to release the drugs; drug release is achieved through the pores, which are formed in the semi permeable wall in situ during the operation. The advantages of controlled porosity osmotic pump tablet are mainly driven by the capacity to deliver drugs in a sustained manner, independent of the drug chemical properties, patient’s physiological factors or concomitant food intake. However, access to this technology has been restricted by the crowded patent landscape and manufacturing challenges. The present review highlights the principle of osmosis, formulation variables, factors affecting drug release, recent researches, marketed products and the evaluation parameters of controlled porosity osmotic pump tablet. 

Keywords: Osmotic pump, Osmotic pressure, Pore forming agent, Osmogen, Wicking agent, excipient