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Formulation and Evalution of Controlled Porosity Osmotic Drug Delivery System of Metoprolol Succinate

A. Abdul Hasan Sathali, G. Magudeswari and K. Arun

The aim of the current study was to develop a controlled porous osmotic pump (CPOP) drug delivery system of metoprolol succinate. The osmotic system utilizes the principle of osmotic pressure, as an energy source for the delivery of drugs. Metoprolol succinate was chosen as a model drug to develop this delivery system because, its plasma half life ranges from 3-4 hrs, its dose is 47.5 mg (equivalent to 50 mg of metoprolol tartrate) and it is required to administer 2-3 times per day. First, an elementary osmotic pump with delivery orifice (0.4 mm) containing drug and osmogens (lactose and fructose) was developed to select suitable osmogen for the development of CPOP drug delivery system. Core tablets containing drug with different osmogens of different ratios were prepared and coated with cellulose acetate (4% w/w) containing diethtylphthalate used as plasticizer. Further, 0.4 mm delivery orifice was drilled on one side of the tablet. From in vitro release studies of this elementary osmotic pump, the formulation containing suitable osmogen was selected for further characterization. The selected formulation was then coated with cellulose acetate containing different concentrations of pore-forming polymers (10% w/w and 20% w/w) (PEG 400 and dibutylphthalate DBP) in the coating membrane. Release studies of the CPOP showed that the coating containing hydrophilic pore forming agents controlled the drug release in a better manner than the hydrophobic pore forming agents. All the formulation follows zero order kinetics and Higuchi equation ensures the drug release follows diffusion mechanism. The IR spectral studies showed no interaction between drug and osmogens. The short term stability studies showed no appreciable changes in drug content.