Physicochemical characterization and dissolution study of solid dispersions of Felodipine with polyethylene glycol 6000

Background: : Felodipine (FEL) is a poorly water-soluble calcium channel blocking agent and widely used for the treatment of hypertension, with problems of variable bioavailability and bio-equivalence related to its poor watersolubility. Therefore, the purpose of this study was to enhance the solubility and dissolution of FEL by complexation with polyethylene glycol 6000 (PEG). Methods: Solid dispersions (SDs) of FEL were prepared in weight ratios of 1:1, 1:2, 1:3, and 1:5 by the hot melt method using PEG as carrier. These SDs were characterized by differential scanning calorimetry (DSC), powder X -ray diffraction (PXRD), and Fourier transform infrared (FTIR) spectroscopy to ascertain whether there were any physicochemical interactions between drug and carrier that could affect dissolution. Solubility and dissolution studies were conducted with pure FEL, physical mixtures (PMs) and SDs. Results: Solubility studies indicated that PEG significantly increased the solubility of FEL in water. The Gibbs free energy (ΔGtr°) values were negative, indicating the spontaneous nature of FEL solubilisation. Phase solubility studies indicated complex with a possible stoichiometry of 1:1. Conclusion: FTIR, DSC and PXRD studies indicate that there is no chemical interaction between FEL and PEG in solid state. In contrast to slow dissolution rate of pure FEL, the dispersion of drug in PEG considerably enhanced the dissolution rate. Even PMs of FEL prepared with PEG also showed better dissolution profiles compared with that of FEL, indicating the solubilisation effect of PEG. Therefore, it is concluded that the preparation of SDs of FEL with PEG provides a promising way to increase its solubility and dissolution rate.