onitoring ibuprofen enantiomers released from polymeric systems

Two methacrylic derivatives of ibuprofen (N-h4-[2-(4-isobutylphenyl)propionyloxy]phenylj methacrylamide (MAI) and 2-[(4-isobutylphenyl)propionyloxy]ethyl methacrylate (MEI)) were used together with 2-hydroxyethyl methacrylate (HEMA) to synthesize four polymeric materials: two hydrophobic homopolymers, PMAI and PMEI, and two hydrophilic copolymers containing 70% (w/w) HEMA, MAI–HEMA 30 and MEI–HEMA 30. The enantiomeric determination of Rand S-IBU released from these four systems has been carried out by capillary electrophoresis. Release of Rand S-IBU was monitored during in vitro assays done at 37 8C at pH 7.4 and 10 in buffered solutions and rat plasma. There is a hydrolytical activation in plasma and at pH 10 compared to pH 7.4; moreover, the release rate from the copolymers is much higher than from the homopolymers as a consequence of the greater hydrophilic character. A slight excess of the S-enantiomer of IBU is observed in all the experiments, being more relevant at higher release rates, i.e. copolymers at pH 10.  2002 Elsevier Science B.V. All rights reserved.