title: Pharmacokinetics of ibuprofen enantiomers in dogs.
abstract: Inversion of inactive (R)-ibuprofen to active (S)-ibuprofen has been suggested to occur presystemically only. In order to investigate the site of inversion in dogs we administered both enantiomers either intravenously or intraduodenally (10 mg/kg) to adult, male beagle dogs (n = 3) in a crossover design. Plasma, urine, and bile were collected for up to 6 h and analyzed stereospecifically by HPLC, according to a previously published method. Pharmacokinetic parameters were calculated using a linear computer program. Absorption after intraduodenal administration occurred rapidly, resulting in maximum plasma concentrations 0.2 h after giving the enantiomer. Approximately 70% of the (R)-enantiomer (according to AUC) was inverted to the S-enantiomer independent of route of administration. No R-ibuprofen could be detected in plasma after (S)-ibuprofen administration. Mean residence time was found to be 2 to 3 times longer for (S)- than for (R)-ibuprofen. Total systemic clearance from plasma was twice as high for (R)- than for (S)-ibuprofen. There were no differences between plasma clearances after intravenous and intraduodenal administration. Between 8 and 17% of dose was recovered in bile [especially as free and conjugated (S)-ibuprofen] and 3-12% in urine [as (S)-ibuprofen, hydroxy- and carboxyibuprofen, free and conjugated forms]. Small amounts of (R)-ibuprofen were detected in bile after intraduodenal administration of (R)-ibuprofen only (1.8% of dose). In short, the unidirectional inversion of R-ibuprofen appears to occur systemically rather than presystemically in dogs.
authors.affiliation: Department of Pharmacology and Toxicology, University of Erlangen-Nuernberg, Federal Republic of Germany.
authors.forename: W S
authors.initials: WS
authors.lastname: Beck
authors.forename: G
authors.initials: G
authors.lastname: Geisslinger
authors.forename: H
authors.initials: H
authors.lastname: Engler
authors.forename: K
authors.initials: K
authors.lastname: Brune
mesh_terms: D000818:Animals; D001646:Bile / Q000378:metabolism; D004285:Dogs; D004386:Duodenum; D004764:Enterohepatic Circulation; D007052:Ibuprofen / Q000008:administration & dosage / Q000737:chemistry / Q000493:pharmacokinetics*; D007275:Injections, Intravenous; D007421:Intestine, Small / Q000378:metabolism; D008297:Male; D013237:Stereoisomerism
chemical_list: D007052:Ibuprofen