Drug formulation is an important aspect of pharmaceutical research. Especially the formulation of
poorly soluble drug compounds can be problematic and can present a serious obstacle for newly
discovered drug compounds to come to application. Among the possible approaches the
development of excipient materials is an attractive option. The interest of the pharmaceutical
research community in silica excipient materials as a means of release control is growing rapidly.
Silica is non toxic and is known for its excellent biocompatibility. In this presentation two new
types of silica excipients are presented.
With the advent of ordered mesoporous silica materials new tools to construct drug delivery
carriers became available. Originally, the focus of mesoporous silica materials has been on the
development of slow release formulations. We demonstrate that the presence of a sufficiently
wide pore diameter is the key for accelerating the release of the poorly soluble drugs such as
itraconazole. The rapid release kinetics can be explained by a displacement desorption of
itraconazole caused by influx of water. The hydrophilicity of the silica pore walls is such that
adsorbed itraconazole molecules are lifted from the surface by competitive adsorption with water
molecules and exported to the surrounding medium (Scheme 1).
Amorphous microporous silica (AMS) materials with subtle variation of porosity were prepared
using an acid-catalyzed sol-gel process departing from tetraethylorthosilicate. Molecules such as
ibuprofen can be molecularly dispersed in the AMS micropores. In vitro buprofen release from
AMS was investigated in simulated intestinal fluid and in a dissolution medium simulating the
gastrointestinal tract with simulated gastric fluid followed by simulated intestinal fluid. AMS has
particular advantages in the controlled release application. Drug release from the silica particles is
controlled by configurational diffusion. The diffusion constant can be varied by orders of
magnitude by adapting the pore diameter. AMS xerogel can be fined to different particle sizes by
crushing and sieving. Ibuprofen release kinetics from AMS can be fine tuned by adjusting AMS
pore diameter and particle size.