GLC Determination of Ibuprofen [dl-2-(p-Isobutylphenyl)propionic Acid] Enantiomers in Biological Specimens

Stereoselective disposition of indoprofen in surgical patients.

“…A stereoselective clearance of an NSAID can be due to a stereoselective elimination, to an inversion of R(-)-enantiomer to S(+)-enantiomer or to a combination of both. This inversion half-life can be estimated at around 10 h for ibuprofen (VanGiessen & Kaiser, 1975) and for benoxaprofen it is a biphasic process with a terminal half-life of 108 ± 3 h (Simmonds et al, 1980). The net change in enantiomer ratio can be expressed as a half-life, after which the ratio has changed from 1:1 to 3: 1 by the real or apparent inversion of half the amount of R(-)-enantiomer.…”

“…A pharmacokinetic study on carprofen in three subjects (Stoltenborg et al, 1981) showed a higher V and clearance for the R(-)-enantiomer and no clear difference in terminal half-life between the enantiomers. Ibuprofen, in a study on three subjects, showed a substantial difference in half-life between the S(+)enantiomer (3.3 h) and the R(-)-enantiomer (2.0 h), which at least in part was due to the rapid inversion of the latter isomer (VanGiessen & Kaiser, 1975). Ibuprofen, in a study on three subjects, showed a substantial difference in half-life between the S(+)enantiomer (3.3 h) and the R(-)-enantiomer (2.0 h), which at least in part was due to the rapid inversion of the latter isomer (VanGiessen & Kaiser, 1975).…”

“…A stereoselective clearance of an NSAID can be due to a stereoselective elimination, to an inversion of R(-)-enantiomer to S(+)-enantiomer or to a combination of both. Stereospecific inversion of R-2-arylpropionic acids, notably ibuprofen (Wechter et al, 1974;VanGiessen & Kaiser, 1975;Kaiser etal., 1976), benoxaprofen (Bopp et al, 1979;Simmonds et al, 1980) and fenoprofen (Rubin et al, 1985) to the S-enantiomers has been demonstrated to occur in vivo in humans. The net change in enantiomer ratio can be expressed as a half-life, after which the ratio has changed from 1:1 to 3: 1 by the real or apparent inversion of half the amount of R(-)-enantiomer.…”

Perioperative pharmacokinetics of ibuprofen enantiomers after rectal administration

“…Plasma (R)-())-and (S)-(+)-ibuprofen were assayed at the same run as (R)-a-methylbenzylamine derivatives with a gas chromatography/mass spectrometry using 3,3-diphenylpropionic acid as internal standard (IS) by a method modified from Vangiessen and Kaiser (14) and Seideman et al (15). About 200 ll of sample was buffered with 1 ml of 0.2 M M H 2 2SO 4 and extracted with 5 ml of toluene containing 150 mlAE100 ml )1 of IS.…”

The Importance of Stereochemistry in the Clinical Pharmacokinetics of the 2-Arylpropionic Acid Non-Steroidal Anti-Inflammatory Drugs

“…indoprofen (Tosolini et aI., 1974), carprofen (Kemmerer et aI., 1979;Stoltenborg et aI., 1981), ibuprofen (Vangiessen and Kaiser, 1975), and naproxen (Goto et aI., 1982). In the cases so far examined in relation to the enantiomeric composition of the material present in plasma, the inactive R-antipode is in general more rapidly eliminated, as indicated by shorter plasma half-life and smaller areas under the plasma concentration-time curves, than the S-enantiomer, e.g.…”