Release studies of different NSAIDs encapsulated in Mg,Al,Fe-hydrotalcites

Layered double hydroxides (LDHs) with Mg²⁺, Al³⁺, and Fe³⁺ in the layers (molar ratios Mg²⁺/M³⁺ = 2, Fe³⁺/(Fe³⁺ + Al³⁺) =0.1) and different non-steroid antiinflammatory drugs, NSAIDs (mefenamic and meclofenamic acids and naproxen) in the interlayer space have been prepared. Anion exchange and coprecipitation procedures have been used, and the solids obtained have been characterised using different physicochemical techniques. The drug content was between 25 and 45% (weight) and depended on the precise nature of the drug and on the preparation procedure. Studies in solution, carried out with samples prepared by anion exchange, have shown a slow dissolution of the drug when intercalated in the inorganic matrix, even slower than when Mg,Al matrices matrixes with the same structure (LDH) were used. Fitting of the experimental data to different kinetics models indicated that the most adequate one is that proposed by Weibull.