Preparation and characterization of pamidronate-loaded PLGA wafer for the treatment of bone resorption

Implantable biodegradable wafers were prepared with pamidronate-loaded poly(L-lactide-co-glycolide) (PLGA, 75:25 mole ratio by lactide to glycolide, molecular weight ; 20000 and 90000 g/mole) by direct compression method for the sustained release of pamidronate to investigate the possibility for the treatment of bone resorption. Pamidronate-loaded PLGA powders were prepared by means of physical mixing and spray drying with the control of formulation factors and characterized by scanning electron microscope and X-ray diffractometer. The pamidronate-loaded PLGA powders fabricated into wafers by direct compression under the constant pressure and time at room temperature. These wafers were also observed for their structural characteristic, release pattern, and degradation pattern. The release rate of pamidronate increased with increasing their initial loading ratio as well as increasing wafer thickness. The molecular weight of PLGA affects the release pattern ; the higher molecular weight of PLGA, the faster release rate. It can be explained that the higher viscosity of high molecular PLGA solution at same concentration tends to aggregate PLGA and pamidronate resulting in unstable pharmaceutical dosage form. This system had advantages in terms of simplicity in design and obviousness of drug release rate and may be useful as an implantable dosage form for the treatment of aural cholesteatoma.