Drug delivery formulations of ordered and nonordered mesoporous silica: comparison of three drug loading methods.

A poorly soluble model drug, indomethacin (IMC), was loaded into two types of silica particles using three different loading methods. The loading efficiency and the extent/rate of drug release were evaluated. Widely used equipment in pharmaceutical laboratories, rotavapor and fluid bed, were used in the loading. The porous materials used were ordered mesoporous silica MCM-41 and nonordered silica gel Syloid 244 FP EU. The materials differ both in their pore properties and particle sizes. Tablets were successfully compressed from the IMC-loaded particles. Mechanical stability of the porous structures was studied with XRPD and nitrogen sorption after tableting and drug release was evaluated at pH 5.5 before and after tableting. The release of the poorly soluble IMC was faster from the Syloid than from the MCM-41, presumably due to the larger pore size and smaller particle size. Loading of IMC into the MCM-41 microparticles improved the drug dissolution, and blending the microparticles with pharmaceutical excipients improved the IMC release even further. The fast release was also maintained after tableting. Loading of IMC into the Syloid particles alone was sufficient to produce similar IMC release profiles, as in the case of MCM-41 with the excipients.