Sol-gel carrier systems for controlled drug delivery

Embedding of the well-known coronary therapeuticum nifedipine into a modified silica matrix by the sol-gel technique allows its releasing behavior to be controlled to a high degree. The liberation rate is proportional to temperature and is increased by the addition of penetration agents such as sorbitol, but is inversely proportional to particle size and is decreased by modification of the silica matrix with methyl-triethoxysilane or polyethyleneglycol. It is presumed that the drug is dispersed in the gel matrix and that diffusion occurs through solvent-filled capillary channels. The liberation rate is governed by the relationship between the rates of dissolution and diffusion.