title: Stereoselective disposition of ibuprofen and flurbiprofen in rats.
abstract: (R)-2-Arylpropionates are often inverted to the pharmacologically active S-enantiomers in vivo, although there is significant interspecies variability in inversion. In order to provide a basis for determining the biochemical consequences of this unique process using rats as a model, it was important to establish the pharmacokinetic disposition of the enantiomers of ibuprofen, a drug well inverted in man and flurbiprofen, a drug apparently poorly inverted in man. Rats were dosed i.v. with a single dose of (R)- or (S)-ibuprofen (20 mg/kg), (R,S)-ibuprofen (40 mg/kg), (R)- or (S)-flurbiprofen (10 mg/kg), or (R,S)-flurbiprofen (20 mg/kg). Each treatment group consisted of six animals. Serial blood samples were withdrawn over a period of 6 h for ibuprofen and 10 h for flurbiprofen. These drugs were assayed in plasma by a stereospecific HPLC assay. The pharmacokinetics of the ibuprofen and flurbiprofen enantiomers were evaluated using a two-compartment open model with conversion of the R- to S-enantiomers in the central compartment. There was 50 +/- 4% inversion of (R)-ibuprofen, a figure similar to that observed in man and (R)-ibuprofen had a higher clearance (12.6 +/- 1.3 ml/min/kg) than (S)-ibuprofen (7.7 +/- 0.7 ml/min/kg; P less than 0.01). The clearance of (R)-flurbiprofen after racemate (2.3 +/- 0.1 ml/min/kg) was higher than its clearance when administered alone (1.7 +/- 0.2 ml/min/kg; P less than 0.01), indicating a pharmacokinetic interaction between the enantiomers (most probably at plasma protein binding sites). A corresponding difference was not observed for ibuprofen. There was a small amount of inversion of (R)-flurbiprofen as determined by area analysis (4.5 +/- 1.6%).(ABSTRACT TRUNCATED AT 250 WORDS)
authors: Department of Clinical Pharmacology and Toxicology, St. Vincent's Hospital, Darlinghurst, Australia.
authors: R D
authors: RD
authors: Knihinicki
authors: R O
authors: RO
authors: Day
authors: G G
authors: GG
authors: Graham
authors: K M
authors: KM
authors: Williams
mesh_terms: D000818:Animals; D005480:Flurbiprofen / Q000097:blood / Q000737:chemistry / Q000493:pharmacokinetics*; D007052:Ibuprofen / Q000097:blood / Q000737:chemistry / Q000493:pharmacokinetics*; D008297:Male; D008657:Metabolic Clearance Rate / Q000187:drug effects; D051381:Rats; D011919:Rats, Inbred Strains; D013237:Stereoisomerism
chemical_list: D005480:Flurbiprofen; D007052:Ibuprofen