Polydimethylsiloxane (PDMS) based adhesives were prepared by cross-linking tetraethoxyorthosilicate (TEOS) while controlling stoichiometry with PDMS, acid catalyst, and water. Particulate additives, alginate and bentonite, were added during the cross-linking process. Cationic drug lidocaine was incorporated into the adhesive with or without additive, and the time-dependent drug release profile was evaluated in phosphate buffered saline and ethanol, respectively. According to kinetic fitting to power function and parabolic diffusion, both solvent and additive type influenced drug release. In particular, particulate additives were found to suppress or facilitate drug release in water or ethanol, respectively.
We prepared pressure-sensitive adhesive (PSA)-containing cross-linked siloxane powders (CS) as a reservoir for a transdermal drug delivery system (TDDS) and evaluated their sustained drug-release properties. PSA, as a patch-type adhesive, was synthesized by a hydrosilylation reaction of vinyl-terminated polysiloxanes with hydrogen-terminated polydimethylsiloxanes. CS was also prepared via a hydrosilylation process with vinyl-terminated polydimethylsiloxane, 1,3,5,7-tetramethyl-1,3,5,7-tetravinyltetracyclosiloxane (D Vi 4 ), hydrogen-terminated polydimethylsiloxane, and dimethylhydrogenmethyl oligomeric siloxane copolymer. The results of release performances using ascorbic acid as a model drug showed a cumulative linear slope over a week, indicating a constant release performance. Our data suggest that this siloxane TDDS could be useful for constant drug release over a long period.
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