Release of ketoprofen enantiomers from HPMC K100M matrices--diffusion studies

Sustained release formulations of ketoprofen elaborated with HPMC K100M were studied to test the hypothesis that chiral excipients can stereoselectively affect the release of the racemic drug. The differences observed in the percentage released between enantiomers show the existence of a chiral interaction between ketoprofen and HPMC K100M. HPMC interacts preferably with the S-enantiomer, although the enantioselectivity observed was not relevant from biopharmaceutical and clinical points of view. Diffusion studies were carried out in membrane diffusion cells to simplify the excipient-drug system and hence to analyze only the influence of diffusion process on the stereoselectivity. The results obtained show that the absence of the erosion process strengthens the enantiomeric differences observed in the drug release from tablets. Another objective of this work was to study the influence of formulation pH on the 'in vitro' release profile of ketoprofen. The amount and the release mechanism of ketoprofen from formulations elaborated are conditioned mainly by the pH of the matrix.