In vitro distribution of ketoprofen enantiomers in articular tissues of osteoarthritic patients

The distribution of ketoprofen enantiomers in joint tissues was studied as a function of their relative tissular affinities using the multi-chamber distribution dialysis system described by Bickel et al. Selected off-cuts of synovial membrane, joint capsule, cartilage and ligament were obtained from ten patients suffering from osteoarthritis of the knee ( n =3) or hip ( n =7). Sorensen solution (4 ml) spiked with racemic ketoprofen (2 μg ml −1 ) was dialysed against 1 ml of the four solutions of tissue homogenates (0.4 g ml −1 ). Ketoprofen enantiomers were quantified in buffer and tissue solutions by high-performance liquid chromatography. The distribution of ketoprofen enantiomers in the Bickel's multi-compartment model indicated that there was a non-stereoselective affinity of ketoprofen enantiomers for their potential target tissues. Despite the interindividual variability in articular tissues, the concentrations (±S.D.) of R - and S -ketoprofen were significantly higher in synovial membrane (8.69 (4.76) μg g −1 for S , 9.14 (5.57) μg g −1 for R ), joint capsule (5.71 (2.49) μg g −1 for S , 5.49 (2.62) μg g −1 for R ) and ligament (6.28 (3.61) μg g −1 for S , 6.40 (3.64) μg g −1 for R ) than in articular cartilage (3.67 (1.75) μg g −1 for S , 3.70 (1.67) μg g −1 for R ). There were no significant differences in the distribution of R - and S -ketoprofen between the solutions of joint capsule, synovium and ligament tissues. These data may be related to differences in ketoprofen affinity for the different constituents of joints. This in vitro distribution profile is similar to that reported in vivo for other non-steroidal anti-inflammatory drugs.