Inclusion of fenofibrate in a series of mesoporous silicas using microwave irradiation

A selection of porous silicas were combined with a model drug using a recently developed, controlled microwave heating process to determine if the application of microwave irradiation could enhance subsequent drug release. Five mesoporous silica types were investigated (core shell, core shell rehydrox, SBA-15, silica gel, SYLOID®) and, for comparison, one non-porous silica (stober). These were formulated using a tailored microwave heating method at drug/excipient ratios of 1:1, 1:3 and 1:5. In addition, all experiments were performed both in the presence and absence of water, used as a fluidising media to aid interaction between drug and support, and compared with results obtained using more traditional heating methods. All formulations were then characterised using differential scanning calorimetry (DSC), powder X-ray diffraction (XRD), scanning electron microscopy (SEM) and Fourier transformation infrared spectroscopy (FT-IR). Pharmaceutical performance was investigated using in vitro drug release studies. A significant enhancement in the release profile of fenofibrate was observed for formulations prepared using microwave heating in the absence of water for five of the six silica based formulations. Of all the formulations analysed, the greatest extent of drug release within the experimental 30 min was the 1:5 core shell rehydrox achieving a total of 86.6 ± 2.8%. The non-porous (stober) particles did not exhibit an increased release of the drug under any experimental conditions studied. This anomaly is thought to be a result of the comparatively small surface area of the silica particles, thus preventing the adsorption of drug molecules.