Stereoselective disposition of carprofen, flunoxaprofen, and naproxen in rats
Iwakawa, S.; Spahn, H.; Benet, L.Z.; Lin, E.T.
Drug Metabolism and Disposition the Biological Fate of Chemicals 19(5): 853-857
1991
ISSN/ISBN: 0090-9556 PMID: 1686227 Document Number: 382788
The stereoselective dispositions of carprofen, flunoxaprofen, and naproxen were studied in rats after i.v. administration of racemate (11 mumol/kg) or enantiomer (5.5 mumol/kg). The total clearances of the (R)-enantiomers of carprofen and flunoxaprofen were significantly greater than those of the (S)-enantiomers. The clearance of (S)-naproxen was similar to the value for (R)-naproxen. There were no marked differences in steady-state volume of distribution between (R)- and (S)-enantiomers for carprofen, flunoxaprofen, or naproxen. The (R)- to (S)-enantiomer inversion ratio for flunoxaprofen in rats was 0.54. The ratios for naproxen and carprofen were 0.02 and 0.003, respectively. Biliary excretion of (R)-carprofen and of its glucuronide were higher than those of the (S)-enantiomer and its glucuronide. In contrast, biliary excretion of the (S)-enantiomers of flunoxaprofen, naproxen, and of their glucuronides were greater than those of their antipodes. Insignificant amounts of the parent enantiomers and of the glucuronides of these three drugs were excreted in urine. These results indicate that there is a wide variation in the extent of inversion at a chiral center for these three 2-arylpropionates and in the stereoselective disposition of their acyl glucuronides.