Elucidation of solution state complexation in wet-granulated oven-dried ibuprofen and β-cyclodextrin:: FT-IR and 1H-NMR studies

The effect of oven-dried wet granulation on the complexation of beta -cyclodextrin with ibuprofen (IBU) in solution was investigated using Fourier transform infrared spectroscopy (FT-IR), proton nuclear magnetic resonance (H-1 NMR), and molecular modeling. Granulation was carried out using 5 mL of three different granulating solvents; water ethanol (95% v/v), and isopropanol and the granules were oven-dried at 60 degreesC for 2 h. The granules were compared to oven-dried physical mixture fi and conventionally prepared complex. Phase solubility study was performed to investigate the stability of the granulation-formed complexes in solution. FT-IR was used to examine the complexation in the granules while H-1 NMR, and molecular modeling studies were carried out to determine the mechanism of complexation in the water-prepared granules. The solubility studies suggested a 1:1 complex between IBU and beta CD. It also showed that the stability of the complex in solution was in the following order with respect to the granulating solvents: ethanol > water > isopropanol. The FT-IR study revealed a shift in the carboxylic acid stretching band and decrease in the intensities of the C-H bending bands of the isopropyl group and the out-of-plane aromatic ring, of IBU, in granules compared to the oven-dried physical mixture. This indicated that granules might have some extent Of solid state complexation that could further enhance dissolution and the IBU-beta CD solution state complexation. H-1 NMR showed that water prepared oven-dried granules had a different H-1 NMR spectrum compared to similarly made oven-dried physical mixture, indicative of complexation in the former The H-1 NMR and the molecular modeling studies together revealed that solution state complexation from the granules occurred by inclusion of the isopropyl group together with part of the aromatic ring of IBU into the beta CD cavity probably through its wider side. These results indicate that granulation process induced faster complexation in solution which enhances the solubility and the dissolution rate of poorly soluble drugs. The extent of complexation in the granules was dependent on the type of solvent used.