Interaction of monovalent cationic drugs with montmorillonite

The aim of this study was to compare the adsorption of various organic drugs and a well-studied surfactant. The organic drugs used were promethazine chloride [10-(2-dimethylammonium) propylfenothiazine chloride] and buformin hydrochloride (1-butylbiguanidine chloride). The surfactant was benzalkonium chloride (N-tridecyl-N-benzyl-N,N-dimethylammonium chloride). Different amounts of drug solutions were added to montmorillonite suspensions, either separately (simple system) or in combination (competitive system) under the same conditions, and the organocomplexes formed were investigated. The organic molecule with the short alkyl chain adsorbed to yield monolayer coverage, whereas the aromatic molecule and the surfactant formed a pseudotrimolecular arrangement. In the competitive system, the larger organic molecules (having the same charge) displaced the smaller one from the interlayer space. The intercalation of molecules in the interlayer space was investigated by X-ray diffraction measurements. Received: 30 November 2000 Revised: 20 December 2001 Accepted: 26 October 2001