Equilibrium and Release Properties of Aqueous Dispersions of Non-Steroidal Anti-Inflammatory Drugs Complexed with Polyelectrolyte Eudragit E 100

Equilibria and release properties of aqueous systems consisting of a set of five non-steroidal anti-inflammatory drugs (AH) complexed with the cationic polymethacrylate Eudragit E 100 (EU) are reported in this study. The composition (EU(AH)₅₀ (HCl)₅₀) having fifty mole percent of each counterion (A⁻ and Cl⁻) produces clear, stable aqueous dispersions in which a remarkably high proportion of AH (higher than 98%) is condensed with the PE under the form of ion pairs. This property expands the interval of pH in which AH are aqueous soluble. The set of AH contains members with and without an alpha methyl group (-(CH₃)CH-COOH: Flurbiprofen, Naproxen, Ketoprofen) and (-CH₂-COOH: Diclofenac, Indomethacin). The proportion of ion pairs in the complexes was lower in the former group. Release of AH from the complexes toward a saline (NaCl 0.9%) solution was assayed in Franz cells. The five complexes behaved as drug carriers that exhibited a slow drug release with a remarkable zero order. In line with the percentages of counterionic condensation observed, release rates from -(CH₃)CH-COOH complexes were clearly higher than those of -CH₂-COOH ones.