ADSORPT ION-DESORPT ION OF SOTALOL HYDROCHLORIDE BY NA-MONTMORILLONITE

isopropylaminoethyl) methane sulfanilide) was studied by means of adsorption isotherms, XRD and IR spectroscopy. The amount of sotalol adsorbed depended on pH, the maximum amount adsorbed (0.56 mEq g-l) being considerably less than the exchange capacity ofthe mineral (0.80 mEq g-l). XRD and IR data revealed that the sotalol is adsorbed into the interlayer space, forming amonolayer complex with a do01 spacing of 17.7 A, and that he mechanisms involved are cation exchange and ion-dipole interactions. Experiments on the in vitro desorption fthe drug from the sotalol-montmorillonite complex indicated that desorption is affected by pH, by the salt concentration f the electrolyte, and by the elimination rate of the desorbed organic cations. Clays are used by the pharmaceutical industry because of their adsorptive, suspension-forming and gel-forming properties (Grim, 1962; Grim & Gfiven, 1978). Other clay properties, however, may open the way to further pharmaceutical use, i.e. their ability to form interlayer complexes with organic molecules, which may enable them to be used as matrices in the preparation of sustained-action formulations, as an alternative to the materials commonly used for such purposes (Stempel, 1966; Robinson, 1978)