Investigation of novel alginate-magnesium aluminum silicate microcomposite films for modified-release tablets

Physicochemical properties of sodium alginate-magnesium aluminum silicate (SA-MAS) composite films were investigated and a potential as a film former of SA-MAS dispersion for modifying drug release from tablets was evaluated as well. Interaction between SA and MAS in the composite films was revealed using FTIR spectroscopy. Thermal behavior of the composite films was changed due to the complexation of SA and MAS. Powder X-ray diffractometry data suggested that a higher crystallinity of the composite film and a phase-separated microcomposite were formed. The composite films in the ratios of 1:0.5 and 1:1 showed the increases of tensile strength and percentage of elongation when compared with SA films. Water vapor permeability of the composite films tended to increase with increasing ratio of MAS. The decreases in water uptake and drug permeability in 0.1 M HCl were found in the composite films. A positive charge drug, propranolol HCl, provided a higher affinity on the composite films than a weakly acidic nonelectrolyte, acetaminophen, resulting in a longer lag time and a higher partition coefficient depending on the content of MAS in the composite films. This was due to the complex formation of propranolol HCl and MAS. Using SEM, the tablets coated with SA-MAS dispersion had a smooth surface, while those with SA dispersion showed a pinholing on the surface, resulting in a faster drug release. The drug release profiles of the tablets could be modified by coating with the composite film at different coating levels. This finding suggests that MAS could improve physicochemical properties of the SA films, leading to a novel coating material of the SA-MAS dispersion for modifying drug release from tablets. (c) 2005 Elsevier B.V. All rights reserved.