Development and Evaluation of Self Pore Forming Osmotic Tablets of Nifedipine

The aim of this study was to formulate and evaluate self pore forming osmotically controlled drug delivery system of Nifedipine. Nifedipine is a dihydropyridine acting as calcium channel blocker with an elimination half life of 2 hours, thereby requiring twice or thrice daily dosing in patients, which may lead to non-compliance. This system was formulated with an intention to achieve zero order release of Nifedipine for 12-13 hours to increase patient compliance by reducing the dosing frequency. Cellulose acetate, a film forming polymer was used with PEG 400 as plasticizer, Potassium chloride as pore forming agent and Acetone and methanol were used as solvents. Combinations of Mannitol-Sucrose, Mannitol-Lactose and Dextrose-Sucrose were used as osmotic agents. This system was developed in two stages: formulation of core tablet and coating of tablet core. Core tablets were evaluated for content uniformity, hardness and weight variation while coated tablets were evaluated for film thickness and in vitro release study. Effect of varying the concentration of pore forming agent on release rate was studied. Effect of various osmogens differing in osmotic pressure on release rate was also evaluated. Though all the formulations exhibited near zero order release, F4 gave maximum drug release at the end of 12^th hour which was fairly constant at 13^th hour.