Abstract
The absorption, metabolism, and excretion of [14C]aprepitant, a potent and selective human substance P receptor antagonist for the treatment of chemotherapy-induced nausea and vomiting, was evaluated in rats and dogs. Aprepitant was metabolized extensively and no parent drug was detected in the urine of either species. The elimination of drug-related radioactivity, after i.v. or p.o. administration of [14C]aprepitant, was mainly via biliary excretion in rats and by way of both biliary and urinary excretion in dogs. Aprepitant was the major component in the plasma at the early time points (up to 8 h), and plasma metabolite profiles of aprepitant were qualitatively similar in rats and dogs. Several oxidative metabolites of aprepitant, derived from N-dealkylation, oxidation, and opening of the morpholine ring, were detected in the plasma. Glucuronidation represented an important pathway in the metabolism and excretion of aprepitant in rats and dogs. An acid-labile glucuronide of [14C]aprepitant accounted for ∼18% of the oral dose in rat bile. The instability of this glucuronide, coupled with its presence in bile but absence in feces, suggested the potential for enterohepatic circulation of aprepitant via this conjugate. In dogs, the glucuronide of [14C]aprepitant, together with four glucuronides derived from phase I metabolites, were present as major metabolites in the bile, accounting collectively for ∼14% of the radioactive dose over a 4- to 24-h period after i.v. dosing. Two very polar carboxylic acids, namely, 4-fluoro-α-hydroxybenzeneacetic acid and 4-fluoro-α-oxobenzeneacetic acid, were the predominant drug-related entities in rat and dog urine.
Footnotes
-
↵1 Abbreviations used are: NK1, neurokinin 1; aprepitant (MK-0869), 5-[[(2R,3S)-2-[(1R)-1-[3,5-bis(trifluoromethyl)phenyl]ethoxy]-3-(4-fluorophenyl)-4-morpholinyl]methyl]-1,2-dihydro-3H-1,2,4-triazol-3-one; SD, Sprague-Dawley; M-1, (2R,3S)-2-[(1R)-1-[3,5-bis(trifluoromethyl)phenyl]ethoxy]-3-(4-fluorophenyl)morpholine; M-2, (2R)-2-[(1R)-1-[3,5-bis(trifluoromethyl)phenyl]ethoxy]-3-(4-fluorophenyl)-5,6-dihydro-2H-1,4-oxazine; M-3, (5S,6R)-6-[(1R)-1-[3,5-bis(trifluoromethyl)phenyl]ethoxy]-5-(4-fluorophenyl)-3-morpholinone; M-4, (6R)-6-[(1R)-1-[3,5-bis(trifluoromethyl)phenyl]ethoxy]-5-(4-fluorophenyl)-5-hydroxy-3-morpholinone; M-5, [(1R)-1-[(1R)-1-[3,5-bis(trifluoromethyl)phenyl]ethoxy]-2-(4-fluorophenyl)-2-oxoethoxy] acetic acid; M-6, [(1R)-1-[(1R)-1-[3,5-bis(trifluoromethyl)phenyl]ethoxy]-2-(4-fluorophenyl)-2-hydroxyethoxy]acetic acid; M-8, (2R,3S)-2-[(1R)-1-[3,5-bis(trifluoromethyl)phenyl]ethoxy]-3-(4-fluorophenyl)-4-morpholineacetic acid; M-9, α-[(R)-[(1R)-[3,5-bis(trifluoromethyl) phenyl]ethoxy](2-hydroxyethoxy) methyl]-4-fluorobenzenemethanol; M-10, 4-fluoro-α-hydroxybenzeneacetic acid; M-11, 4-fluoro-α-oxobenzeneacetic acid; M-12, 4-fluorophenylglycine; M-13, (αS)-4-fluoro-α-[[(2,5-dihydro-5-oxo-1H-1,2,4-triazol-3-yl)methyl] amino]benzeneacetic-carboxy acid; M-14, 5-[[(1S)-1-(4-fluorophenyl)-2-hydroxyethyl-2-amino]methyl]-1,2-dihydro-3H-1,2,4-triazol-3-one; HPLC, high-performance liquid chromatography; LC-MS/MS, liquid chromatography-tandem mass spectrometry; TFA, trifluoroacetic acid; MEK, methyl ethyl ketone; NOE, nuclear Overhauser effect.
- Received June 13, 2003.
- Accepted October 2, 2003.
- The American Society for Pharmacology and Experimental Therapeutics
DMD articles become freely available 12 months after publication, and remain freely available for 5 years.Non-open access articles that fall outside this five year window are available only to institutional subscribers and current ASPET members, or through the article purchase feature at the bottom of the page.
|