Stereoselective reversible binding properties of the glucuronide conjugates of fenoprofen enantiomers to human serum albumin.

The stereoselective binding of fenoprofen enantiomers and fenoprofen glucuronide diastereomers to human serum albumin (HSA) was investigated using an ultrafiltration method. Fenoprofen glucuronides exhibit a considerable and stereoselective affinity to HSA, although less than seen for the parent drug. The (R)-glucuronide shows a higher affinity to HSA than the (S)-diastereomer. With the enantiomers, no significant difference could be detected. Diazepam and probenecid reduced the binding of the glucuronides, as well as that of the fenoprofen enantiomers. These results suggest that parent drug and its glucuronide metabolites occupy the same binding region on the albumin molecule. Both fenoprofen enantiomers, as well as racemic fenoprofen, are capable of reducing the extent of reversibly bound fenoprofen glucuronide.