Controlled release solid dispersion of metoprolol succinate for direct use in the preparation of multiple strengths solid dosage forms

Solid dispersions are an established solubilisation technique for water insoluble drugs. These are essentially drug-polymer systems that are able to improve the dissolution and bioavailability profiles of water insoluble drugs owing to greater drug-polymer interactions. The purpose of this study was to exploit these drug-polymer interactions in solid dispersions to develop sustained release dosage forms of a water soluble drug, Metoprolol Succinate.;The solid dispersions were prepared by solvent evaporation method, using formulations containing various ratios of drug and rate controlling polymer and a lipid excipient. Drug release profiles were determined by the USP Apparatus 1 (Basket Apparatus) in phosphate buffer solution (pH 6.8). The solid dispersion formulations were characterised by analytical methods like powder XRD, FT-IR, DSC and UV spectroscopy to check for amorphous nature and hydrogen bonding interactions between drug and polymers.;Among all the formulations studied, the dispersion sample containing Drug/ Methocel RTM K 100 Premium LV/Compritol RTM 888 ATO in a weight ratio of 1: 1.5:0.5 gave the desired sustained Among all the formulations studied, the dispersion sample containing Drug/ Methocel K100 Premium LV/Compritol RTM 888 ATO in a weight ratio of 1: 1.5: 0.5 gave the desired sustained release profile for the 24 hr period. When compared against the pure drug and the physical mixture of the same formulation, the results showed that the drug release was sustained due to the formation of the solid dispersion and not merely due to the presence of the rate controlling polymers and lipid excipient.;To evaluate the feasibility of developing multiple strength dosage forms of this particular drug formulation, the dispersion powder equivalent to 25 mg, 50 mg, 100 mg, and 200 mg were tested for the drug-release profiles. The data revealed that the drug release was proportionate to the amount of drug present in the dispersion formulation. Further, a graph of % drug released vs time was found to be almost over lapping. This strengthens the proposition that multiple dosage strengths can be conveniently formulated using this particular method and formula.;The pXRD and DSC data confirmed the amorphous nature of the drug in the formulation. The FT-IR data was inconclusive for hydrogen bonding interactions because of overlapping of the IR absorption peaks in the formulation sample. Furthermore, the stability studies performed for a duration of 1 month at 45 °C by pXRD and DSC suggested no change in the amorphous nature of the formulation sample.