Solid dispersion of prednisolone: solid state characterization and improvement of dissolution profile

Background: Dissolution testing is an important test for judging the effectiveness of a pharmaceutical dosage form. Many drugs create adverse effect because of insufficient solubility at the physiological pH. This study is aimed to improve the dissolution properties of prednisolone (PRD) that falls under the category of class II biopharmaceutics system. Methods: In this study, preparation of solid dispersions with various water-soluble carriers was studied to improve the dissolution of PRD. To obtain the optimized formulation, solid dispersions were prepared employing different methods using different carriers with various drug: carrier ratios. Their dissolution behaviors were also compared. Fourier transform infrared (FTIR) spectroscopy, powder X-ray diffraction, and thermal analysis were studied to characterize the prepared solid dispersion. Results: PRD formed stable complexes with carriers as indicated by the stability constants (K-a) of 9.5-597.2 M-1. The results indicated that in vitro dissolution rate of PRD was remarkably improved in the solid dispersion of the drug compared with physical mixture and drug alone. This can be attributed to improved wettability, dispersibility, decrease in crystallinity, and increase in amorphous fraction of the drug. The results obtained from Fourier transform infrared spectroscopy and powrer X-ray diffraction showed good evidence of drug-carrier interaction while using carriers such as hydroxypropyl-beta-cyclodextrin (HP-beta CD) and polyethylene glycol (PEG). Crystallinity of the drug was reduced in the solid dispersions prepared with hydroxypropyl-beta-cyclodextrin, polyvinylpyrrolidone-co-vinyl acetate 64, and PEG as revealed from the differential scanning calorimetry thermograms. Conclusion: The results suggested that the solid dispersion with selected excipients is a powerful tool to accelerate the dissolution of poorly water-soluble drugs.