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Xue C, Segabinazzi L, Hall A, Dzikiti TB, French H, Gilbert R. A retrospective comparison of postoperative outcomes in ovariectomised jennies (Equus asinus) treated with phenylbutazone or flunixin meglumine. Equine Vet J 2024; 56:1170-1182. [PMID: 38500306 DOI: 10.1111/evj.14082] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/30/2023] [Accepted: 02/25/2024] [Indexed: 03/20/2024]
Abstract
BACKGROUND Clinically, flunixin meglumine (FM) and phenylbutazone (PBZ) are preferentially selected for the treatment of visceral and musculoskeletal pain, respectively, in horses. In donkeys, there is no information to support or refute this conventional conjecture. OBJECTIVES To compare postoperative outcomes in a group of jennies treated with intravenous FM or oral PBZ. ANIMALS Fourteen jennies unilaterally ovariectomised by standing left flank laparotomy. STUDY DESIGN Retrospective cohort study. METHODS Data from medical records of ovariectomised jennies (case details, weight, non-steroidal anti-inflammatory drug [NSAID] protocol, surgery duration, operative sequence, anaesthesia protocol, physical examination findings and outcomes) were collected. From collated data, postoperative adverse events were defined as fever, tachycardia, tachypnea, inappetence, altered mentation, abnormal oral mucous membranes, bruxism, colic, incisional complications (i.e., drainage, oedema, peri-incisional emphysema and pain) and non-survival, then further divided into occurrence during the early (≤24 h) or late (>24 h) postoperative period for data analysis using R software. Chi-squared test was used to compare individual adverse events between groups (PBZ vs. FM) and moments (early vs. late). Significance was set at p ≤ 0.05. RESULTS PBZ treatment (8/14) was associated with (odds ratio, 95% confidence interval) more total (2.93, 1.97-4.36), early (3.01, 1.87-4.84) and late (2.69, 1.28-5.63) adverse events than FM treatment (6/14). Tachycardia (37.83, 2.21-646.66), tachypnoea (0.29, 0.13-0.66), altered mentation (2.78, 1.01-7.67), altered mucous membranes (18.38, 1.04-325.23), incisional oedema (44.33, 2.60-754.5) and incisional pain (47.78, 2.81-811.61) were significantly different between groups. Early adverse events significantly different between groups included tachycardia (50.2, 2.9-877.0), altered mentation (3.33, 1.08-10.29) and incisional pain (21.0, 1.2-374.5), with late adverse events being tachypnea (0.07, 0.01-0.62), incisional oedema (32.92, 1.85-584.28) and incisional pain (28.92, 1.62-515.68). Colic (2/8) and non-survival (1/8) were rare events that only occurred in the PBZ cohort and could not be further evaluated for differences. MAIN LIMITATIONS Small sample size; retrospective study; treatment bias; varied administration routes. CONCLUSIONS Oral PBZ may be inappropriate to use following abdominal surgery in donkeys. CLINICAL RELEVANCE More prospective and case-controlled studies are needed to evaluate the clinical efficacy of these two NSAIDs in donkeys.
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Affiliation(s)
- Cynthia Xue
- Department of Clinical Sciences, Ross University School of Veterinary Medicine, Basseterre, St. Kitts, West Indies
| | - Lorenzo Segabinazzi
- Department of Clinical Sciences, Ross University School of Veterinary Medicine, Basseterre, St. Kitts, West Indies
| | - Alexis Hall
- Department of Clinical Sciences, Ross University School of Veterinary Medicine, Basseterre, St. Kitts, West Indies
| | - Tarisai Brighton Dzikiti
- Department of Clinical Sciences, Ross University School of Veterinary Medicine, Basseterre, St. Kitts, West Indies
| | - Hilari French
- Department of Clinical Sciences, Ross University School of Veterinary Medicine, Basseterre, St. Kitts, West Indies
| | - Robert Gilbert
- Department of Clinical Sciences, Ross University School of Veterinary Medicine, Basseterre, St. Kitts, West Indies
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Gray B, Lubbock K, Love C, Ryder E, Hudson S, Scarth J. Analytical advances in horseracing medication and doping control from 2018 to 2023. Drug Test Anal 2024. [PMID: 39010718 DOI: 10.1002/dta.3760] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/27/2024] [Revised: 06/07/2024] [Accepted: 06/20/2024] [Indexed: 07/17/2024]
Abstract
The analytical approaches taken by laboratories to implement robust and efficient regulation of horseracing medication and doping control are complex and constantly evolving. Each laboratory's approach will be dictated by differences in regulatory, economic and scientific drivers specific to their local environment. However, in general, laboratories will all be undertaking developments and improvements to their screening strategies in order to meet new and emerging threats as well as provide improved service to their customers. In this paper, the published analytical advances in horseracing medication and doping control since the 22nd International Conference of Racing Analysts and Veterinarians will be reviewed. Due to the unprecedented impact of COVID-19 on the worldwide economy, the normal 2-year period of this review was extended to over 5 years. As such, there was considerable ground to cover, resulting in an increase in the number of relevant publications included from 107 to 307. Major trends in publications will be summarised and possible future directions highlighted. This will cover developments in the detection of 'small' and 'large' molecule drugs, sample preparation procedures and the use of alternative matrices, instrumental advances/applications, drug metabolism and pharmacokinetics, the detection and prevalence of 'endogenous' compounds and biomarker and OMICs approaches. Particular emphasis will be given to research into the potential threat of gene doping, which is a significant area of new and continued research for many laboratories. Furthermore, developments in analytical instrumentation relevant to equine medication and doping control will be discussed.
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Knych HK, McKemie DS, Kass PH, Stanley SD, Blea J. Ketoprofen in horses: Metabolism, pharmacokinetics, and effects on inflammatory biomarkers. Drug Test Anal 2024; 16:289-302. [PMID: 37439283 DOI: 10.1002/dta.3543] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/05/2023] [Revised: 06/23/2023] [Accepted: 06/26/2023] [Indexed: 07/14/2023]
Abstract
Ketoprofen is an anti-inflammatory drug that is commonly administered to racehorses for the alleviation of musculoskeletal pain and inflammation. This study represents a comprehensive examination of the metabolism (in vivo and in vitro), pharmacokinetics and ex vivo pharmacodynamics, of ketoprofen in horses. The in vitro metabolism as well as specific enzymes responsible for metabolism was determined by incubating liver microsomes and recombinant CYP450 and UGT enzymes with ketoprofen. For the in vivo portion, 15 horses were administered a single intravenous dose of 2.2-mg/kg ketoprofen. Blood and urine samples were collected prior to and up to 120 h post-drug administration. Additional blood samples were collected at select time points and were stimulated with calcium ionophore or lipopolysaccharide, ex vivo, to induce eicosanoid production. Drug, metabolite, and eicosanoid concentrations were determined using LC-MS/MS. Incubation of ketoprofen with equine liver microsomes generated 3-hydroxy ketoprofen, an unidentified hydroxylated metabolite, and ketoprofen glucuronide. Recombinant equine CYP2C23 produced the greatest amount of hydroxylated ketoprofen and recombinant equine UGT1A2 generated ketoprofen glucuronide. Dihydro, 3-hydroxy, and glucuronide metabolites were identified in blood and urine samples. The Vdss was 0.280, 0.385, and 0.319 L/kg for total ketoprofen, S (+) ketoprofen, and R (-) ketoprofen, respectively. The mean half-life was 6.01 h for total ketoprofen, 2.22 h for S (+) ketoprofen, and 1.72 h for R (-) ketoprofen. Stimulation of ketoprofen-treated blood with lipopolysaccharide and calcium ionophore resulted in an inhibition of TXB2 , PGE2 , PGF2alpha , LTB4 , and 15(s)-HETE production for up to 120 h post-drug administration.
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Affiliation(s)
- Heather K Knych
- K.L. Maddy Equine Analytical Pharmacology Laboratory, School of Veterinary Medicine, University of California, Davis, California, USA
- Department of Veterinary Molecular Biosciences, School of Veterinary Medicine, University of California, Davis, California, USA
| | - Daniel S McKemie
- K.L. Maddy Equine Analytical Pharmacology Laboratory, School of Veterinary Medicine, University of California, Davis, California, USA
| | - Philip H Kass
- Department of Population Health and Reproduction, School of Veterinary Medicine, University of California, Davis, California, USA
| | - Scott D Stanley
- MH Gluck Equine Research Center, University of Kentucky College of Agriculture, Lexington, Kentucky, USA
| | - Jeff Blea
- School of Veterinary Medicine, University of California, Davis, California, USA
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Kemp KL, Skinner JE, Bertin F. Effect of phenylbutazone on insulin secretion in horses with insulin dysregulation. J Vet Intern Med 2024; 38:1177-1184. [PMID: 38363029 PMCID: PMC10937495 DOI: 10.1111/jvim.17013] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/01/2023] [Accepted: 01/26/2024] [Indexed: 02/17/2024] Open
Abstract
BACKGROUND Phenylbutazone is often prescribed to manage pain caused by hyperinsulinemia-associated laminitis, but in diabetic people nonsteroidal anti-inflammatory drugs increase insulin secretion and pancreatic activity. HYPOTHESIS/OBJECTIVES Investigate the effect of phenylbutazone administration on insulin secretion in horses. It was hypothesized that phenylbutazone will increase insulin secretion in horses with insulin dysregulation (ID). ANIMALS Sixteen light breed horses, including 7 with ID. METHODS Randomized cross-over study design. Horses underwent an oral glucose test (OGT) after 9 days of treatment with phenylbutazone (4.4 mg/kg IV q24h) or placebo (5 mL 0.9% saline). After a 10-day washout period, horses received the alternative treatment, and a second OGT was performed. Insulin and glucose responses were compared between groups (ID or controls) and treatments using paired t test and analyses of variance with P < .05 considered significant. RESULTS In horses with ID, phenylbutazone treatment significantly decreased glucose concentration (P = .02), glucose area under the curve (2429 ± 501.5 vs 2847 ± 486.1 mmol/L × min, P = .02), insulin concentration (P = .03) and insulin area under the curve (17 710 ± 6676 vs 22 930 ± 8788 μIU/mL × min, P = .03) in response to an OGT. No significant effect was detected in control horses. CONCLUSION AND CLINICAL IMPORTANCE Phenylbutazone administration in horses with ID decreases glucose and insulin concentrations in response to an OGT warranting further investigation of a therapeutic potential of phenylbutazone in the management of hyperinsulinemia-associated laminitis beyond analgesia.
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Affiliation(s)
- Kate L. Kemp
- School of Veterinary ScienceThe University of QueenslandGatton, QueenslandAustralia
| | - Jazmine E. Skinner
- School of Agriculture and Environmental ScienceUniversity of Southern QueenslandDarling Heights, QueenslandAustralia
| | - François‐René Bertin
- School of Veterinary ScienceThe University of QueenslandGatton, QueenslandAustralia
- College of Veterinary MedicinePurdue UniversityWest‐LafayetteIndianaUSA
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Peraza J, Hector RC, Lee S, Terhaar HM, Knych HK, Wotman KL. Ocular penetration of oral acetaminophen in horses. Equine Vet J 2023; 55:899-904. [PMID: 36482840 DOI: 10.1111/evj.13902] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/15/2022] [Accepted: 11/24/2022] [Indexed: 12/13/2022]
Abstract
BACKGROUND Acetaminophen (paracetamol) is increasingly used to treat painful conditions in horses but its ocular penetration has not been studied. OBJECTIVES To determine whether orally administered acetaminophen penetrates the aqueous humour of the normal equine eye and report an aqueous humour:serum acetaminophen concentration ratio in horses. STUDY DESIGN In vivo experiment. METHODS Six privately owned horses with normal ophthalmic examinations weighing 568 ± 65 kg (mean ± standard deviation) and aged 11 ± 4 years were given 20 mg/kg acetaminophen orally every 12 h for a total of six doses. Physical exam parameters were recorded prior to, during, and after the dosing period. One hour after the final dose, horses were sedated and simultaneous aqueous humour and serum samples were collected and analysed for acetaminophen concentrations and selected eicosanoids. An aqueous humour:serum acetaminophen concentration ratio was calculated. A second aqueous humour sample was taken and analysed for eicosanoid concentrations 3 months after acetaminophen dosing. Physical exam data were compared between time points using a mixed model analysis (significance p < 0.05). RESULTS Acetaminophen was detected in both serum and aqueous humour of all horses and mean ± standard deviation aqueous humour:serum acetaminophen concentration ratio was 44.9 ± 15.9%. No significant changes in physical exam parameters occurred during or after dosing. Eicosanoids were not detected in aqueous humour at any sampling point. MAIN LIMITATIONS Presence of acetaminophen in the aqueous humour may not relate to clinical effect. A therapeutic level of acetaminophen has not been determined in horses, and the absence of ocular inflammation does not reflect conditions in which acetaminophen may be used. CONCLUSIONS Acetaminophen readily penetrates the aqueous humour of the normal equine eye after consecutive oral dosing. Further study is required to determine whether acetaminophen is useful in the treatment of ocular pain and inflammation.
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Affiliation(s)
- Jacky Peraza
- Department of Clinical Sciences, Colorado State University, Fort Collins, Colorado, USA
| | - Rachel C Hector
- Department of Clinical Sciences, Colorado State University, Fort Collins, Colorado, USA
| | - Sera Lee
- Department of Clinical Sciences, Colorado State University, Fort Collins, Colorado, USA
| | - Hannah M Terhaar
- Department of Clinical Sciences, Colorado State University, Fort Collins, Colorado, USA
| | - Heather K Knych
- Department of Clinical Sciences, Colorado State University, Fort Collins, Colorado, USA
| | - Kathryn L Wotman
- Department of Clinical Sciences, Colorado State University, Fort Collins, Colorado, USA
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Mercer MA, Davis JL, McKenzie HC. The Clinical Pharmacology and Therapeutic Evaluation of Non-Steroidal Anti-Inflammatory Drugs in Adult Horses. Animals (Basel) 2023; 13:1597. [PMID: 37238029 PMCID: PMC10215112 DOI: 10.3390/ani13101597] [Citation(s) in RCA: 5] [Impact Index Per Article: 5.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/21/2022] [Revised: 04/19/2023] [Accepted: 04/21/2023] [Indexed: 05/28/2023] Open
Abstract
This review firstly examines the underlying pathophysiology of pain and inflammation associated with orthopedic disease and endotoxemia. Then, it reviews the clinical pharmacology (pharmacokinetics and pharmacodynamics) of both conventional and non-conventional NSAIDs in the adult horse, and finally provides an overview of different modalities to evaluate the therapeutic efficacy of NSAIDs in research.
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Affiliation(s)
- Melissa A. Mercer
- Department of Biological Sciences and Pathobiology, Virginia Maryland College of Veterinary Medicine, Blacksburg, VA 24061, USA
| | - Jennifer L. Davis
- Department of Biological Sciences and Pathobiology, Virginia Maryland College of Veterinary Medicine, Blacksburg, VA 24061, USA
| | - Harold C. McKenzie
- Department of Large Animal Clinical Sciences, Virginia Maryland College of Veterinary Medicine, Blacksburg, VA 24061, USA
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Tou K, Cawley A, Bowen C, Bishop DP, Fu S. Towards Non-Targeted Screening of Lipid Biomarkers for Improved Equine Anti-Doping. MOLECULES (BASEL, SWITZERLAND) 2022; 28:molecules28010312. [PMID: 36615506 PMCID: PMC9822433 DOI: 10.3390/molecules28010312] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Figures] [Subscribe] [Scholar Register] [Received: 12/08/2022] [Revised: 12/22/2022] [Accepted: 12/24/2022] [Indexed: 01/03/2023]
Abstract
The current approach to equine anti-doping is focused on the targeted detection of prohibited substances. However, as new substances are rapidly being developed, the need for complimentary methods for monitoring is crucial to ensure the integrity of the racing industry is upheld. Lipidomics is a growing field involved in the characterisation of lipids, their function and metabolism in a biological system. Different lipids have various biological effects throughout the equine system including platelet aggregation and inflammation. A certain class of lipids that are being reviewed are the eicosanoids (inflammatory markers). The use of eicosanoids as a complementary method for monitoring has become increasingly popular with various studies completed to highlight their potential. Studies including various corticosteroids, non-steroidal anti-inflammatories and cannabidiol have been reviewed to highlight the progress lipidomics has had in contributing to the equine anti-doping industry. This review has explored the techniques used to prepare and analyse samples for lipidomic investigations in addition to the statistical analysis and potential for lipidomics to be used for a longitudinal assessment in the equine anti-doping industry.
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Affiliation(s)
- Kathy Tou
- Centre for Forensic Science, University of Technology Sydney, Sydney, NSW 2007, Australia
- Correspondence:
| | - Adam Cawley
- Australian Racing Forensic Laboratory, Racing NSW, Sydney, NSW 2000, Australia
| | - Christopher Bowen
- Mass Spectrometry Business Unit, Shimadzu Scientific Instruments (Australasia), Sydney, NSW 2116, Australia
| | - David P. Bishop
- Hyphenated Mass Spectrometry Laboratory (HyMAS), University of Technology, Sydney, NSW 2007, Australia
| | - Shanlin Fu
- Centre for Forensic Science, University of Technology Sydney, Sydney, NSW 2007, Australia
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Knych HK, Arthur RM, Gretler SR, McKemie DS, Goldin S, Kass PH. Pharmacokinetics of transdermal flunixin meglumine and effects on biomarkers of inflammation in horses. J Vet Pharmacol Ther 2021; 44:745-753. [PMID: 34173263 DOI: 10.1111/jvp.12993] [Citation(s) in RCA: 3] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/27/2020] [Revised: 04/02/2021] [Accepted: 06/08/2021] [Indexed: 11/30/2022]
Abstract
Flunixin meglumine is a highly efficacious nonsteroidal anti-inflammatory drug commonly used in equine medicine and especially in performance horses. Recently, a new transdermal flunixin meglumine product has been approved for use in cattle. Although not currently approved for use in the horse, the convenience of this product may prove appealing for use in horses, warranting study. Six horses were administered a single transdermal dose of 500 mg and blood and urine samples collected for up to 96 h post-administration. Serum for determination of thromboxane concentrations and whole blood samples was collected at various time and challenged with lipopolysaccharide, calcium ionophore, or methanol to induce ex vivo synthesis of eicosanoids. Concentrations of flunixin, 5-OH flunixin, and eicosanoids were measured using LC-MS/MS and non-compartmental pharmacokinetic analysis performed on concentration data. Serum concentrations of flunixin and 5-OH flunixin were above the limit of quantitation at 96 h post-administration in both serum and urine. The mean (range) for Cmax , Tmax and the terminal half-life were 515.6 (369.7-714.0) ng/ml, 8.67 (8.0 12.0) h, and 22.4 (18.3-42.5) h, respectively. Following transdermal administration, based on effects on eicosanoid synthesis, flunixin meglumine inhibited cyclooxygenase 1 and 2 and 15-lipooxygenase activity, with anti-inflammatory effects lasting for 24-72 h.
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Affiliation(s)
- Heather K Knych
- K.L. Maddy Equine Analytical Pharmacology Laboratory, School of Veterinary Medicine, University of California, Davis, California, USA.,Department of Veterinary Molecular Biosciences, School of Veterinary Medicine, University of California, Davis, California, USA
| | - Rick M Arthur
- School of Veterinary Medicine, University of California, Davis, California, USA
| | - Sophie R Gretler
- K.L. Maddy Equine Analytical Pharmacology Laboratory, School of Veterinary Medicine, University of California, Davis, California, USA
| | - Daniel S McKemie
- K.L. Maddy Equine Analytical Pharmacology Laboratory, School of Veterinary Medicine, University of California, Davis, California, USA
| | - Skyler Goldin
- K.L. Maddy Equine Analytical Pharmacology Laboratory, School of Veterinary Medicine, University of California, Davis, California, USA
| | - Philip H Kass
- Department of Population Health and Reproduction, School of Veterinary Medicine, University of California, Davis, California, USA
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Knych HK, Finno CJ, Baden R, Arthur RM, McKemie DS. 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 2020; 44:36-46. [PMID: 32757313 DOI: 10.1111/jvp.12891] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/11/2020] [Revised: 06/15/2020] [Accepted: 06/25/2020] [Indexed: 11/29/2022]
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.
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Affiliation(s)
- Heather K Knych
- 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
| | - Carrie J Finno
- Department of Population Health and Reproduction, School of Veterinary Medicine, University of California, Davis, Davis, CA, USA
| | - Russell Baden
- K.L. Maddy Equine Analytical Pharmacology Laboratory, School of Veterinary Medicine, University of California-Davis, Davis, CA, USA
| | - Rick M Arthur
- School of Veterinary Medicine, University of California, Davis, Davis, CA, USA
| | - Daniel S McKemie
- K.L. Maddy Equine Analytical Pharmacology Laboratory, School of Veterinary Medicine, University of California-Davis, Davis, CA, USA
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Knych HK, Arthur RM, McKemie DS, Baden RW, Seminoff K, Kass PH. Pharmacokinetics and anti-inflammatory effects of flunixin meglumine as a sole agent and in combination with phenylbutazone in exercised Thoroughbred horses. Equine Vet J 2020; 53:102-116. [PMID: 32145701 DOI: 10.1111/evj.13260] [Citation(s) in RCA: 4] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/02/2019] [Revised: 02/20/2020] [Accepted: 03/02/2020] [Indexed: 01/16/2023]
Abstract
BACKGROUND Flunixin meglumine (FM) and phenylbutazone (PBZ) are potent anti-inflammatory agents and as such their potential to mask injuries that would otherwise keep a horse from training or racing is concerning. A common practice in racetrack medicine in the USA is to administer the two drugs within close proximity (24 hours apart) of each other, raising the concern of pharmacokinetic interactions and enhanced anti-inflammatory effects. OBJECTIVES Describe the pharmacokinetics and effects of PBZ on the clearance of FM when administered in close proximity as well as effects on inflammatory mediators. STUDY DESIGN Two-way randomised balanced crossover experiment. METHODS Twelve Thoroughbred exercised horses received 500 mg FM IV alone or in combination with 2 g of IV PBZ 24 hours later. Blood and urine samples were collected prior to and for up to 120 hours post-drug administration. Whole blood samples were collected at various times and challenged with lipopolysaccharide or calcium ionophore to induce ex vivo synthesis of eicosanoids. Concentrations of FM, PBZ and eicosanoids were measured using LC-MS/MS and noncompartmental pharmacokinetic analysis performed on concentration data. RESULTS Flunixin meglumine clearance was significantly increased when horses received PBZ 24 hours post-administration (P = .03). No other differences in pharmacokinetic parameters were noted between groups. Thromboxane B2 was significantly suppressed, relative to baseline for 96 hours post-FM administration. Subsequent administration of PBZ prolonged the suppression. Prostaglandin E2 was decreased for 24 hours following administration of FM with subsequent administration of PBZ prolonging the suppression until 120 hours. PGF2alpha concentrations were decreased for up to 168 hours post-FM administration. FM administration significantly decreased 15-HETE. MAIN LIMITATIONS Small sample size and lack of a phenylbutazone-only treatment group. CONCLUSIONS Administration of PBZ post-FM administration increased FM clearance. The anti-inflammatory effects of FM appear to be prolonged when PBZ is administered 24 hours post-administration.
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Affiliation(s)
- Heather K Knych
- K.L. Maddy Equine Analytical Pharmacology Laboratory, School of Veterinary Medicine, University of California, Davis, CA, USA.,Department of Veterinary Molecular Biosciences, School of Veterinary Medicine, University of California, Davis, CA, USA
| | - Rick M Arthur
- School of Veterinary Medicine, University of California, Davis, CA, USA
| | - Daniel S McKemie
- K.L. Maddy Equine Analytical Pharmacology Laboratory, School of Veterinary Medicine, University of California, Davis, CA, USA
| | - Russell W Baden
- K.L. Maddy Equine Analytical Pharmacology Laboratory, School of Veterinary Medicine, University of California, Davis, CA, USA
| | - Kelsey Seminoff
- K.L. Maddy Equine Analytical Pharmacology Laboratory, School of Veterinary Medicine, University of California, Davis, CA, USA
| | - Philip H Kass
- Department of Population Health and Reproduction, School of Veterinary Medicine, University of California, Davis, CA, USA
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