Dissolution studies of povidone–sulfathiazole coacervated systems

Sulfathiazole and povidone were coacervated by many methods, indicating complexation of the two compounds. The coacervated complex had a higher solubility and dissolution rate than did sulfathiazole. It resisted the action of dilute acids and alkalies, suggesting a helical structure with sulfathiazole situated between two povidone chains and a hydrogen bond linking the amino groups of the sulfathiazole to the oxygen of povidone. Upon addition of precipitants for sulfathiazole, the povidone portion attempted to compensate and to solubilize the whole complex; hence, partial precipitation or coacervation occurred. A model is given to describe the dissolution profile of the different coacervate systems prepared.