Characterisation of Gliclazide-PEG 8000 Solid Dispersions

Purpose: The aim of the present study was to characterise gliclazide solid dispersions (SDs) prepared with polyethylene glycol (PEG) 8000 and compare them with SDs in PEG 6000.
Methods: Gliclazide SDs containing varying concentrations of PEG 8000 were prepared using the fusion – solvent technique, and their phase solubility behavior and dissolution in 0.1N HCl were assessed at 37°C. The physical state of, and gliclazide-PEG interactions in, SDs and physical mixtures prepared in ratios of 1:1, 1:2 and 1:5 (gliclazide: PEG 8000), respectively, were characterized by x-ray diffraction (XRD), Fourier-transform infrared (FTIR) spectroscopy and differential scanning calorimetry (DSC).
Results: The solubility of gliclazide increased with increasing amount of PEG 8000 in aqueous medium. Gibbs free energy (ΔGo tr) values were all negative, indicating the spontaneous nature of gliclazide solubilisation. Dissolution studies indicated a significant increase in the dissolution of gliclazide when dispersed in PEG 8000. FTIR analysis demonstrated the absence of well-defined gliclazide - PEG 8000 chemical interaction while DSC and XRD studies indicated the amorphous /microcrystalline state of gliclazide in the SDs.
Conclusion: In both solid dispersions and physical mixture, PEG 8000 increases the solubility and dissolution rate of gliclazide. The increased dissolution rate of gliclazide may be due to the formation of microcrystals, increased wettability and dispersibility in systems containing PEG 8000.

Keywords
Gliclazide, Solid dispersion, PEG 8000, Dissolution, Solubility, X-ray diffraction, FT-IR, DSC.