In vitro release of citrate anions intercalated in magnesium aluminium layered double hydroxides

Layered double hydroxides (LDHs) present a potential application in medicine, as matrices, when intercalated with organic anions of pharmaceutical interest. Once encapsulated, the drug can be released at a rate, depending on the pH of the solution, which may be due to the destruction of the layer by acid attack. The main objective of this work was to evaluate Mg(II)-Al(III)-LDHs for the sustained release of citrate. The citrate intercalated LDHs were prepared by the constant pH coprecipitation technique followed by hydrothermal treatment. Materials were characterized by PXRD, FT-IR, SEM, specific surface area, mean pore diameter analysis, and in vitro release. The release studies were made in a dissolution system that simulates in vivo conditions, obeying the sink conditions. The amount of citrate released, which was determined by HPLC, was 63.8% within 12 h. The total amount released was less than that observed with physical mixture (100%). Thus, these systems seem to be promising for the sustained release of citrate. The data followed the Higuchi square root law (r > 0.98) during the release. (C) 2003 Elsevier Ltd. All rights reserved.