Alkyl-substituted silica gel as a carrier in the controlled release of dexmedetomidine

The effect of alkyl substitution of the silica xerogel matrix on the releas e rate of dexmedetomidine was evaluated. Silica sol was processed by either casting or spray drying. When the reaction precursor tetraethylorthosilica te (TEOS) was partially substituted with tri- or dialkoxysilane, the releas e of dexmedetomidine and degradation of the matrix were decreased compared with 100% TEOS-based gel. Increasing the number or length of the organic gr oups attached to silicon, modified the silica gel structure and reduced the release rate of dexmedetomidine from monoliths. The release of dexmedetomi dine from alkyl-substituted silica gel microparticles, however. showed a bu rst in drug release. Subcutaneously administered silica xerogel matrices (m anufactured by casting, containing 25 mol% dimethyidiethoxysilane at two di fferent doses of dexmedetomidine) were studied in dogs. Sustained delivery of dexmedetomidine was obtained for at least 48 h. (C) 2001 Elsevier Scienc e B.V. All rights reserved.