Identification and characterization of the enzymes responsible for the metabolism of the non-steroidal anti-inflammatory drugs, flunixin meglumine and phenylbutazone, in horses.
Abstract: The in vivo metabolism and pharmacokinetics of flunixin meglumine and phenylbutazone have been extensively characterized; however, there are no published reports describing the in vitro metabolism, specifically the enzymes responsible for the biotransformation of these compounds in horses. Due to their widespread use and, therefore, increased potential for drug-drug interactions and widespread differences in drug disposition, this study aims to build on the limited current knowledge regarding P450-mediated metabolism in horses. Drugs were incubated with equine liver microsomes and a panel of recombinant equine P450s. Incubation of phenylbutazone in microsomes generated oxyphenbutazone and gamma-hydroxy phenylbutazone. Microsomal incubations with flunixin meglumine generated 5-OH flunixin, with a kinetic profile suggestive of substrate inhibition. In recombinant P450 assays, equine CYP3A97 was the only enzyme capable of generating oxyphenbutazone while several members of the equine CYP3A family and CYP1A1 were capable of catalyzing the biotransformation of flunixin to 5-OH flunixin. Flunixin meglumine metabolism by CYP1A1 and CYP3A93 showed a profile characteristic of biphasic kinetics, suggesting two substrate binding sites. The current study identifies specific enzymes responsible for the metabolism of two NSAIDs in horses and provides the basis for future study of drug-drug interactions and identification of reasons for varying pharmacokinetics between horses.
© 2020 John Wiley & Sons Ltd.
Publication Date: 2020-08-05 PubMed ID: 32757313PubMed Central: PMC7875478DOI: 10.1111/jvp.12891Google Scholar: Lookup
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Summary
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The research article is about identifying and analysing the enzymes responsible for metabolising non-steroidal anti-inflammatory drugs, flunixin meglumine and phenylbutazone, in horses.
Objective of the Study
- The study was conducted to identify and understand the enzymes that contribute to the metabolism of flunixin meglumine and phenylbutazone in horses.
Background and Importance of the Study
- The metabolism and pharmacokinetics of the said drugs have been studied in vivo; however, there had been no published reports on their in vitro metabolism, particularly the enzymes responsible for their biotransformation in horses.
- These drugs are widely used and hence have a higher possibility for drug-drug interactions and ability to affect drug disposition differently.
Methodology
- The researchers incubated the drugs with equine liver microsomes and a panel of recombinant equine P450s.
- Phenylbutazone’s incubation in microsomes led to the generation of oxyphenbutazone and gamma-hydroxy phenylbutazone.
- The incubation of flunixin meglumine with microsomes resulted in the production of 5-OH flunixin, indicating possible substrate inhibition.
Findings
- In the recombinant P450 assays, only equine CYP3A97 was found capable of producing oxyphenbutazone.
- Members of the equine CYP3A family and CYP1A1 were found capable of transforming flunixin to 5-OH flunixin.
- Flunixin meglumine metabolism by CYP1A1 and CYP3A93 showed a profile characteristic of biphasic kinetics, implying the presence of two substrate binding sites.
- The study identified specific enzymes responsible for the metabolism of the two NSAIDs in horses.
Significance
- The findings of this study set grounds for future research on drug-drug interactions and the differences in the pharmacokinetics among horses.
Cite This Article
APA
Knych HK, Finno CJ, Baden R, Arthur RM, McKemie DS.
(2020).
Identification and characterization of the enzymes responsible for the metabolism of the non-steroidal anti-inflammatory drugs, flunixin meglumine and phenylbutazone, in horses.
J Vet Pharmacol Ther, 44(1), 36-46.
https://doi.org/10.1111/jvp.12891 Publication
Researcher Affiliations
- K.L. Maddy Equine Analytical Pharmacology Laboratory, School of Veterinary Medicine, University of California-Davis, Davis, CA, USA.
- Department of Veterinary Molecular Biosciences, School of Veterinary Medicine, University of California, Davis, Davis, CA, USA.
- Department of Population Health and Reproduction, School of Veterinary Medicine, University of California, Davis, Davis, CA, USA.
- K.L. Maddy Equine Analytical Pharmacology Laboratory, School of Veterinary Medicine, University of California-Davis, Davis, CA, USA.
- School of Veterinary Medicine, University of California, Davis, Davis, CA, USA.
- K.L. Maddy Equine Analytical Pharmacology Laboratory, School of Veterinary Medicine, University of California-Davis, Davis, CA, USA.
MeSH Terms
- Animals
- Anti-Inflammatory Agents, Non-Steroidal / chemistry
- Anti-Inflammatory Agents, Non-Steroidal / metabolism
- Anti-Inflammatory Agents, Non-Steroidal / pharmacokinetics
- Clonixin / analogs & derivatives
- Clonixin / chemistry
- Clonixin / metabolism
- Clonixin / pharmacokinetics
- Cytochrome P-450 Enzyme System / metabolism
- DNA, Complementary / genetics
- DNA, Complementary / metabolism
- Gene Expression Regulation, Enzymologic / drug effects
- Horses / metabolism
- Microsomes, Liver / metabolism
- Molecular Structure
- Phenylbutazone / chemistry
- Phenylbutazone / metabolism
- Phenylbutazone / pharmacokinetics
Grant Funding
- L40 TR001136 / NCATS NIH HHS
- California Horse Racing Board
Conflict of Interest Statement
CONFLICT OF INTEREST. All authors declare no conflicts of interest.
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