In vitro release of dexmedetomidine from silica xerogel monoliths: effect of sol-gel synthesis parameters.

Dexmedetomidine, an alpha 2-agonist, was incorporated as a hydrochloride salt into silica xerogel in order to evaluate the effect of sol-gel synthesis parameters: pH of the sol, water/alkoxide molar ratio, drug concentration and size of the device on the drug release rate and degradation rate of the matrix. This study showed that diffusion controlled the release of dexmedetomidine from silica xerogel prepared between pH 1 and pH 5. The drug release was, however, slowest near the zero charge of silica xerogel (pH 2-3). The burst of dexmedetomidine, a lipophilic, but in the form of hydrochloride salt water-soluble drug, was increased from the matrix prepared either below or above the isoelectric point. It follows that the optimum pH for preparing a drug delivery device for dexmedetomidine, is near the zero charge of silica xerogel, where the degradation of the matrix was also slowest. In addition to processing pH, the release rate of drugs can be controlled by changing the water/alkoxide molar ratio of the sol.