Polyelectrolyte-drug ionic complexes as nanostructured drug carriers to design solid and liquid oral delivery systems

Abstract

Aqueous dispersions of acid or basic polyelectrolytes (PE) loaded with ionizable drugs (D) of opposite charge are characterized by a high degree of counterionic condensation. In solid state, these PE-D complexes are stable amorphous materials that, in many cases, quickly swell reverting to the original dispersion in the presence of aqueous fluids. Such systems exhibit a set of unique properties. Among them, the reversibility of the PE-D association modulates the release of D when dispersions are in contact with biological fluids. Besides, some of them exhibit interesting bioadhesive properties. By compaction of solid complexes swellable PE-D matrices (SPDM) are obtained. Kinetics and rate of D delivery from SPDM can be modulated by changes in their composition to satisfy the design of extended delivery systems. Among the factors that control the delivery of D, the rate of swelling, complex dissociation of ionic pairs and further diffusion of D, as well as hydrogel layer erosion, are mainly involved. PE-D complexes formulated as matrices, multiparticulate or dispersed systems play an important role in the design of drug delivery systems.