Gabapentin, a human therapeutic medication and an environmental substance transferring at trace levels to horses: a case report.
Abstract: Gabapentin, 1-(Aminomethyl)cyclohexaneacetic acid, MW 171.240, is a frequently prescribed high dose human medication that is also used recreationally. Gabapentin is orally absorbed; the dose can be 3,000 mg/day and it is excreted essentially unchanged in urine. Gabapentin is stable in the environment and routinely detected in urban wastewater. Gabapentin randomly transfers from humans to racing horses and is at times detected at pharmacologically ineffective / trace level concentrations in equine plasma and urine. In Ohio racing between January 2019 and July 2020,18 Gabapentin identifications, all less than 2 ng/ml in plasma, were reported. These identifications were ongoing because the horsemen involved were unable to pin down and therefore avoid the source of these identifications. Given that 44 ng/ml or less is an Irrelevant Plasma Concentration (IPC) of Gabapentin in horses, we proposed a 5 ng/ml plasma interim Screening Limit of Detection for Gabapentin identifications in Ohio racing, and an essentially similar 8 ng/ml plasma Screening Limit of Detection was suggested by a scientific advisor to the Ohio Horse Racing Commission. As such, an analytical Screening Limit of 8 ng /ml in plasma is an appropriate and pharmacologically conservative analytical "cut-off" or Screening Limit of Detection (SLOD) for Gabapentin in equine competitive events to avoid the calling of "positive" identifications on random unavoidable trace level identifications of this widely prescribed human therapeutic medication in equine forensic samples.
© 2022. The Author(s).
Publication Date: 2022-10-04 PubMed ID: 36192810PubMed Central: PMC9531455DOI: 10.1186/s13620-022-00226-5Google Scholar: Lookup
The Equine Research Bank provides access to a large database of publicly available scientific literature. Inclusion in the Research Bank does not imply endorsement of study methods or findings by Mad Barn.
- Journal Article
Summary
This research summary has been generated with artificial intelligence and may contain errors and omissions. Refer to the original study to confirm details provided. Submit correction.
The research article discusses the trace presence of Gabapentin, a medication usually prescribed for humans, in racehorses, and proposes a threshold for what should be considered trace detection versus a “positive” result for the medication in equine blood tests.
Overview of Gabapentin and its Presence in Horses
- Gabapentin is a common human medication, often used in high dosages and is also used recreationally. It is absorbed orally, and is generally excreted unchanged in urine. This medication is also stable in the environment and is frequently detected in urban wastewater.
- Interestingly, Gabapentin is found to randomly transfer from humans to racehorses, and is sometimes detected in trace, or pharmacologically ineffective, levels in horse plasma and urine.
Gabapentin in Ohio Racing Horses
- Blood screening in Ohio racing between January 2019 and July 2020 detected 18 Gabapentin identifications, all less than 2 ng/ml, in horse plasma. The cause of these identifications was unknown, as the horsemen involved were unable to identify and thus avoid the source of this medication in the horses.
- Given that a concentration of 44 ng/ml or less is regarded as an inconsequential plasma concentration of Gabapentin in horses, the researchers propose a 5 ng/ml plasma interim screening limit of detection for Gabapentin in Ohio racing.
Proposed Analytical Screening Limit for Gabapentin
- A scientific advisor to the Ohio Horse Racing Commission suggested a similar plasma screening limit of detection — 8 ng/ml. According to the researchers, an analytical Screening Limit of 8 ng/ml in plasma is an suitable and conservatively pharmacological “cut-off” or Screening Limit of Detection (SLOD) for Gabapentin in equine competitive events.
- This proposal aims to prevent the declaration of “positive” identifications based on trace level identifications of Gabapentin, which could arise given its wide prescription as a human therapeutic medication and its ability to transfer, at trace levels, to horses.
Cite This Article
APA
Brewer K, Machin J, Maylin G, Fenger C, Morales-Briceño A, Tobin T.
(2022).
Gabapentin, a human therapeutic medication and an environmental substance transferring at trace levels to horses: a case report.
Ir Vet J, 75(1), 19.
https://doi.org/10.1186/s13620-022-00226-5 Publication
Researcher Affiliations
- , Wellington, FL, USA.
- The Maxwell H. Gluck Equine Research Center and Department of Toxicology and Cancer Biology, University of Kentucky, Lexington, Kentucky, 40546, USA.
- New York Drug Testing and Research Program, 777 Warren Rd, Ithaca, NY, 14853, USA.
- Equine Integrated Medicine, 4904 Ironworks Rd., Georgetown, KY, 40324, USA.
- Emirates Endurance Village, Stable 28, Alain Stud-Al Wathba, Abu Dhabi, United Arab Emirates.
- The Maxwell H. Gluck Equine Research Center and Department of Toxicology and Cancer Biology, University of Kentucky, Lexington, Kentucky, 40546, USA. ttobin@uky.edu.
Grant Funding
- 101 / The Equine Health and Welfare Alliance, Inc, Versailles, Kentucky
- 201 / the United States Trotting Association, Columbus, OH.
- 7001029 / National Institute of Food and Agriculture, U.S. Department of Agriculture, Hatch Program under project KY014066 Accession Number 7001029.
- 201 / The National Horsemen's Benevolent and Protective Association and the Alabama, Arizona, Arkansas, Ontario, Canada; Charles Town, WV; Florida, Indiana, Iowa, Kentucky, Louisiana, Michigan, Minnesota, Nebraska, Ohio, Oklahoma, Oregon, Pennsylvania, Tampa Bay
Conflict of Interest Statement
The authors cite no competing interests or specific funding other than those referenced in acknowledgements. All authors contributed to the review, analysis and drafting of the manuscript and all reviewed and approved the final product for publication. Authors KB, CF, AMB, GAM and TT are researchers and participants in areas of equine forensic science and have presented and at times testified as experts such matters. The corresponding author, TT, and author CF have at times advised parties with respect to matters involving Gabapentin identifications.
References
This article includes 18 references
- . Final Test Report. dated October 9th, 2109.
- Mays T. Positive Letter. dated November 21st, 2019.
- Personal communication 8/13/2020 to TT by Mr. Kerry Holloway Association of Racing Commissioners International of an updated listing of ARCI recorded Gabapentin regulatory “positives”.
- . Gabapentin Positives in Plasma (January 1, 2019, to July 30, 2020). Ohio Department of Agriculture response of 9/2/2020 to public records request 200808.
- Gutierrez J, Eisenberg RL, Koval NJ, Armstrong ER, Tharappel J, Hughes CG, Tobin T. Pemoline and tetramisole 'positives' in english racehorses following levamisole administration.. Ir Vet J 2010 Aug 1;63(8):498.
- Maylin G, Fenger C, Machin J, Kudrimoti S, Eisenberg R, Green J, Tobin T. Aminorex identified in horse urine following consumption of Barbarea vulgaris; a preliminary report.. Ir Vet J 2019;72:15.
- Goodman CW, Brett AS. A Clinical Overview of Off-label Use of Gabapentinoid Drugs.. JAMA Intern Med 2019 May 1;179(5):695-701.
- Pharmacy OSB. Reports and statistics gabapentin prescriptions per 100K residents by month. Ohio Automated Rx Reporting System: OARRS Accessed 12 Mar 2022.
- del Amo EM, Urtti A, Yliperttula M. Pharmacokinetic role of L-type amino acid transporters LAT1 and LAT2.. Eur J Pharm Sci 2008 Oct 2;35(3):161-74.
- Gurke R, Rößler M, Marx C, Diamond S, Schubert S, Oertel R, Fauler J. Occurrence and removal of frequently prescribed pharmaceuticals and corresponding metabolites in wastewater of a sewage treatment plant.. Sci Total Environ 2015 Nov 1;532:762-70.
- Brewer K, Fenger C, Machin J, Catignani M, Tobin T. Gabapentin: a classic human medication transferring in trace amounts to racing horses. The Horseman's J 2020.
- Personal communications to TT by Mr. Darryl Vienna, Esq., 5256 S. Mission Road, Suite 703 - #808, Bonsall, CA 92003 communicated 6/11/2021 concerning Gabapentin “positives” in California horseracing.
- Toutain PL, Lassourd V. Pharmacokinetic/pharmacodynamic approach to assess irrelevant plasma or urine drug concentrations in postcompetition samples for drug control in the horse.. Equine Vet J 2002 May;34(3):242-9.
- Heltsley R, Depriest A, Black DL, Robert T, Caplan YH, Cone EJ. Urine drug testing of chronic pain patients. IV. prevalence of gabapentin and pregabalin.. J Anal Toxicol 2011 Jul;35(6):357-9.
- Terry RL, McDonnell SM, Van Eps AW, Soma LR, Liu Y, Uboh CE, Moate PJ, Driessen B. Pharmacokinetic profile and behavioral effects of gabapentin in the horse.. J Vet Pharmacol Ther 2010 Oct;33(5):485-94.
- Machin J, Brewer K, Catignani M. An interim screening limit of detection for naproxen in equine plasma: a review and analysis. Comp Exerc Physiol 2020;16(2):153–160.
- Sams RA. Reporting Recommendations for Specific Substances. Memorandum provided to M. Ryzmek at the Ohio State Racing Commission on or about November 19th, 2019.
- O’Connor B. Coolmore vet loses “winner” due to drug in family dog. The Irish Times Friday June 17th 2022.
Citations
This article has been cited 0 times.Use Nutrition Calculator
Check if your horse's diet meets their nutrition requirements with our easy-to-use tool Check your horse's diet with our easy-to-use tool
Talk to a Nutritionist
Discuss your horse's feeding plan with our experts over a free phone consultation Discuss your horse's diet over a phone consultation
Submit Diet Evaluation
Get a customized feeding plan for your horse formulated by our equine nutritionists Get a custom feeding plan formulated by our nutritionists
