Interaction between Eudragit® E100 and anionic drugs: Addition of anionic polyelectrolytes and their influence on drug release performance

Abstract

In this work, we report results concerning the study of solid complexes compounded by a cationic polymethacrylate (Eudragit® E100, Eu) and mesalazine (M) (Eu–Mx complex). The influence of an anionic polyacrylic acid polymer (carbomer, C) on dissolution behavior of M from the complex was evaluated (Eu–MxCy complex). The dissolution profiles and solvent front movements of solid matrices in different media (water, buffer pH 7.4, 0.9% NaCl) were investigated and ionic interactions among Eu, M, and C were determined through Fourier transform infrared (FT‐IR) spectroscopy. For Eu–Mx complexes, the affinity between M and Eu modulated the delivery of free M in solution, with the dissolution media affecting the delivery rate mainly due to an ionic interchange process between M and anionic electrolytes (i.e., Cl−). FTIR spectroscopy allowed the ionic interaction between Eu and M to be verified. The addition of C (Eu–MxCy) influenced the dissolution behavior of these matrices. As the amount of C was increased, the release mechanism changed from diffusion (Eu–M50) or anomalous (Eu–M100) to zero order (Eu–MxC50). This variation in rate delivery was also affected by the dissolution media, as occurred with Eu–Mx complexes. The formation of the gel layer during the dissolution process, as consequence of Eu–MxCy matrices hydration, was influenced by C amount and dissolution media. © 2011 Wiley‐Liss, Inc. and the American Pharmacists Association J Pharm Sci 100:4664–4673, 2011