Intercalation compounds of hydrotalcite-like anionic clays with antiinflammatory agents--I. Intercalation and in vitro release of ibuprofen.

Hydrotalcite-like compounds are layered solids having positively charged layers and interlayer charge-compensating anions. The synthetic Mg0.67Al0.33(OH)2 Cl0.33.0.6H2O, which is biocompatible, has been used to intercalate a model drug, ibuprofen, in order to prepare a modified release formulation. The intercalation compound was prepared via ion-exchange starting from the chloride form of hydrotalcite and its composition, determined both by elemental microanalysis and thermogravimetric analysis, was Mg0.67Al0.33(OH)2IBU0.33.0.47H2O, drug content 50% (w/w). As a consequence of the intercalation, the interlayer distance of the host increased from 0.78 nm (interlayer distance of chloride form) to 2.17 nm. The result of dissolution tests at pH 7.5 showed that the in vitro drug release was modified if compared with that obtained with comparative formulations. The mechanism of modified drug release has been interpreted on the basis of the ion exchange process of the ibuprofen anion intercalated in the lamellar host and phosphates contained in the intestinal fluid buffer.