Abstract

This study describes the application of three non-ordered mesoporous silicas (Syloid AL-1, Syloid 72 and Syloid 244) in improving the dissolution rate of a poorly aqueous soluble drug, namely gemfibrozil. For this purpose, solid dispersions were formulated using a robust and controlled microwave heating method. Prepared formulations were subjected to solid state characterisation and dissolution behaviour. Differential scanning calorimetry (DSC) and X-ray diffraction (XRD) results confirmed that microwave heating method incorporated gemfibrozil in an amorphous form in Syloid 72 and Syloid 244. This was attributed to a large pore volume and diameter compared with Syloid AL-1 which has a small pore volume. Presence of more crystalline drug in the case of Syloid AL-1 based formulations was attributed to larger surface area where drug was adsorbed in layers as confirmed by the scanning electron microscopy. DSC and XRD results also confirmed stability of formulations when stored for 3 months under stressed conditions (40 °C and 75% RH). FT-IR results show lack of interaction between silica and the drug in all cases. It was also noted that all three silica types improved the dissolution behaviour of gemfibrozil when compared with dissolution properties of pure drug. The surface properties of Syloid 72 were found optimum as it enhanced the rate of dissolution of gemfibrozil from microwave processed formulation far better than physically mixed formulations and those prepared with Syloid AL-1 and Syloid 244.

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