Inclusion complexes of Theophylline (THP) with β-cyclodextrin (β−CD) were prepared in order to improve the solubility and bioavailability of the poorly water soluble drug. Solution phase interaction was studied by UV-Vis and Fluorescence techniques. The linear Benesi– Hildebrand plot indicated the formation of only one type of complex with a host-guest composition of 1:1 in the solution. The effect of method of preparation of the THP-β−CD inclusion complexes (ICs) was investigated. The ICs were prepared by the conventional methods of physical mixing (PM), kneading (KN), co-precipitation (CP) and freeze drying (FD) and also by the novel approach of microwave irradiation method (MW). The solid inclusion complexes were characterized by various spectroscopic techniques such as FTIR, XRD, DSC, SEM and 1H NMR. The characterization techniques indicated the formation of true inclusion complexes in case of CP, FD and MW. The in vitro dissolution rate of THP was considerably enhanced when the inclusion complexes were employed. Therefore, the bioavailability of THP can be improved significantly by forming inclusion complexes with cyclodextrin
