Swellable drug–polyelectrolyte matrices (SDPM) of alginic acid: Characterization and delivery properties

This study deals with the development and characterization of the delivery properties of swellable drug–polyelectrolyte matrices (SDPM) of alginic acid (AA). Complexes (AA–D)x in solid state were obtained by neutralization of AA with different molar proportions (x) of model basic drugs (D), in which D is atenolol, metoclopramide and propranolol. They were characterized by DSC, IR and X-ray diffraction.Matrices prepared by compaction of (AA–D)x alone or in a mixture with sodium alginate (NaAA) were subjected to measurements of solvent up-take, release kinetics and erosion in three media (water, buffer of pH 6.8 and 0.01 M HCl). In addition, the dynamics of swelling was also evaluated. All SDPM assayed exhibited a remarkable zero order of delivery in water and buffer of pH 6.8 and also in two-step delivery experiments: 2 h in acid medium followed by a second step at pH 6.8. Experimental results indicate that the erosion of the hydrogel layer is the main delivery process. Delivery rate, can be modulated either by varying the composition of (AA–D)x or by diluting it with NaAA.