Chemiadsorbates of Drugs on Silica: A New Approach to Drug Release Modification

Abstract

The preparation, characterization and in-vitro release of 2-phenylethylal-cohol and thymol chemiadsorbates on a porous silica support of mean pore size of 10 nm are described. Drug molecules are linked to the silica surface by =Si-O-C= bonds via their alcoholic or their phenolic group, respectively. UV and IR spectroscopy were used to identify the chemiadsorbates and to characterize the adsorbed state of the drug molecules. The in-vitro release of the active component from this type of immobilized drug was found to be dependent on drug structure, the preparation technique (surface coverage of the chemiadsorbate) and the pH of the dissolution fluid. In the latter case increasing rates of release occured by increasing the pH. The release profiles are discussed here, considering the possible use of these chemiadsorbates in drug release modification.