Matrix

Sintering is defined as the thermal treatment of a powder or compact at a temperature below the melting point of the main constituent, for the purpose of increasing its bond strength. This concept in pharmaceutical science is relatively new, but research works relating to this process have been growing. Sintering has been described as the mechanism for the strengthening of the mechanical properties of consolidated pharmaceutical powders at elevated temperatures, for solid-bond formation during tablet compression, and for thermal curing of polymer-latex film -Coatings. The changes in the microstructures, Hardness, Friability, Wettability, disintegration time and dissolution rate of tablets stored at elevated temperature were also described as a result of sintering. Controlled release oral dosage forms were developed by sintering the polymer matrix by exposing to temperature above glass transition (Tg) point of the polymer. In the application of thermal sintering technique to the formulation of controlled release dosage form, the main research focus has been on the influence of sintering on the alteration of the microstructures in a polymeric matrix and the release of the active ingredients from the matrix.

The present work was aimed to develop a 24 hour modified release dosage form of model drug propranolol HCl using different waxes by hot melt granulation technique. Three waxes: stearic acid, cetostearyl alcohol and glyceryl behenate were used at 5%, 10%, 15% 20% and 30% concentration in matrix systems. Prepared formulations showed good tabletting characteristics. The effect of various waxes and their concentrations were studied on the release of the drug. The drug release profile from the wax matrices were tired to match with targeted dissolution profile (TDP). Matrix systems containing 30% stearic acid showed dissolution profile similar to TDP for initial hours and later the release was slower than TDP. In case of matrix system containing 30% cetostearyl alcohol, the drug release was within the TDP and with systems containing glyceryl behenate, propranolol HCl release was within TDP with 10%, 15% and 20% concentration. The release of drug was slower than TDP for matrix system containing 30% glyceryl behenate. The matrix system showing drug release within TDP followed non- Fickian diffusion.