Abstract
Background: Enflicoxib is a non-steroidal anti-inflammatory drug of the coxib family characterized by a long-lasting pharmacological activity that has been attributed to its active metabolite E-6132.
Objectives: The aim of this work was to explore enflicoxib biotransformation In vitro in humans, rats and dogs, and to determine its metabolic pathways.
Methods: Different In vitro test systems were used, including hepatocytes and liver and non-hepatic microsomes. The samples were incubated with enflicoxib and/or any of its metabolites at 37°C for different times depending on the test system. The analyses were performed by liquid chromatography coupled with either radioactivity detection or high-resolution mass spectrometry.
Results: Enflicoxib was efficiently metabolized by cytochrome P-450 into three main phase I metabolites: M8, E-6132, and M7. The non-active hydroxy-pyrazoline metabolite M8 accounted for most of the fraction metabolized in all the three species. The active pyrazol metabolite E-6132 showed a slow formation rate, especially in dogs, whereas metabolite M7 was a secondary metabolite formed by oxidation of M8. In hepatocytes, diverse phase II metabolite conjugates were formed, including enflicoxib glucuronide, M8 glucuronide, E-6132 glucuronide, M7 glucuronide, and M7 sulfate. Metabolite E-6132 was most probably eliminated by a unique glucuronidation reaction at a very low rate.
Conclusion: The phase I metabolism of enflicoxib was qualitatively very similar among rats, humans and dogs. The low formation and glucuronidation rates of the active enflicoxib metabolite E-6132 in dogs are postulated as key factors underlying the mechanism of its long-lasting pharmacokinetics and enflicoxib's overall sustained efficacy.
Keywords: Enflicoxib, metabolism, CYP, COX-2, dog, rat, humans.
Graphical Abstract
[http://dx.doi.org/10.1593/tlo.08160] [PMID: 19252746]
[http://dx.doi.org/10.1016/j.intimp.2010.07.013] [PMID: 20709632]
[http://dx.doi.org/10.1016/j.bmc.2007.11.079] [PMID: 18158247]
[http://dx.doi.org/10.1002/jhet.3118]
[http://dx.doi.org/10.1002/1522-2683(200206)23:11<1702::AID-ELPS1702>3.0.CO;2-#] [PMID: 12179991]
[http://dx.doi.org/10.1002/bdd.258] [PMID: 11754039]
[http://dx.doi.org/10.1111/jvp.12995]
[http://dx.doi.org/10.1016/j.yrtph.2007.10.007] [PMID: 18060673]
[http://dx.doi.org/10.1111/jvp.12757] [PMID: 30888074]
[http://dx.doi.org/10.1016/j.tvjl.2021.105625]
[http://dx.doi.org/10.1124/dmd.31.4.491] [PMID: 12642477]
[http://dx.doi.org/10.1124/dmd.31.11.1398] [PMID: 14570773]
[http://dx.doi.org/10.1111/j.1365-2885.2007.00840.x] [PMID: 17472652]