Sol-gel carrier systems for controlled drug delivery

Embedding of the well-known coronary therapeuticum nifedipine into a modifi ed silica matrix by the sol-gel technique allows its releasing behavior to be controlled to a high degree. The liberation rate is proportional to temp erature and is increased by the addition of penetration agents such as sorb itol, but is inversely proportional to particle size and is decreased by mo dification of the silica matrix with methyl-triethoxysilane or polyethylene glycol. It is presumed that the drug is dispersed in the gel matrix and tha t diffusion occurs through solvent-filled capillary channels. The liberatio n rate is governed by the relationship between the rates of dissolution and diffusion.