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Lidocaine in the horse: its pharmacological effects and their relationship to analytical findings.
Abstract: Lidocaine is a local anaesthetic agent that is widely used in equine medicine. It is also an Association of Racing Commissioners International (ARCI) Class 2 foreign substance that may cause regulators to impose substantial penalties if residues are identified in post race urine samples. Therefore, an analytical/pharmacological database was developed for this drug. Using our abaxial sesamoid local anaesthetic model, the highest no-effect dose (HNED) for the local anaesthetic effect of lidocaine was determined to be 4 mg. Using enzyme-linked immunosorbent assay (ELISA) screening, administration of the HNED of lidocaine to eight horses yielded peak serum and urine concentrations of apparent lidocaine of 0.84 ng/mL at 30 min and 72.8 ng/mL at 60 min after injection, respectively. These concentrations of apparent lidocaine are readily detectable by routine ELISA screening tests (LIDOCAINE ELISA, Neogen, Lexington, KY). ELISA screening does not specifically identify lidocaine or its metabolites, which include 3-hydroxylidocaine, dimethylaniline, 4-hydroxydimethylaniline, monoethylglycinexylidine, 3-hydroxymonoethylglycinexylidine, and glycinexylidine. As 3-hydroxylidocaine is the major metabolite recovered from equine urine, it was synthesized, purified and characterized, and a quantitative mass spectrometric method was developed for 3-hydroxylidocaine as recovered from horse urine. Following subcutaneous (s.c.) injection of the HNED of lidocaine, the concentration of 3-hydroxylidocaine recovered from urine reached a peak of about 315 ng/mL at 1 h after administration. The mean pH of the 1 h post dosing urine samples was 7. 7, and there was no apparent effect of pH on the amount of 3-hydroxylidocaine recovered. Within the context of these experiments, the data suggests that recovery of less than 315 ng/mL of 3-hydroxylidocaine from a post race urine sample is unlikely to be associated with a recent local anaesthetic effect of lidocaine. Therefore these data may be of assistance to industry professionals in evaluating the significance of small concentrations of lidocaine or its metabolites in postrace urine samples. It should be noted that the quantitative data are based on analytical methods developed specifically for this study, and that methods used by other laboratories may yield different recoveries of urine 3-hydroxylidocaine.
Publication Date: 1999-01-14 PubMed ID: 9885969DOI: 10.1046/j.1365-2885.1998.00165.xGoogle 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
- Research Support
- Non-U.S. Gov't
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 paper studies the impact and detection of Lidocaine, an anaesthetic drug used in horses, tracing levels of the drug and its metabolites in the horse’s system post dosage to identify the highest no effect dose. This can assist racing industry officials to evaluate the presence of Lidocaine in post-race samples.
Objective of the Study
- The primary aim of this research paper was to understand and document the pharmacological effects of the drug Lidocaine on horses. Lidocaine, a local anaesthetic agent, has notable impact on the performance of racing horses and its detection in post-racing urine samples can lead to severe penalties.
- The study aimed to determine the highest no-effect dose (HNED) of Lidocaine, which signifies the maximum dose of the medication that will not cause any identifiable side effects or performance enhancements.
Methods of Study
- The study used an abaxial sesamoid local anaesthetic model and determined the HNED of Lidocaine as 4 mg.
- To test the presence and concentration of Lidocaine, eight horses were administered with the determined HNED, and their serum and urine samples studied at different intervals using enzyme-linked immunosorbent assay (ELISA).
- The ELISA screening could identify the presence of Lidocaine in detectable concentrations of 0.84ng/mL in serum (after 30 mins of administration) and 72.8ng/mL in urine samples (after 60 minutes of administration).
- Furthermore, a quantitative mass spectrometric method was developed and employed, focusing on 3-hydroxylidocaine, the main metabolite of Lidocaine found in equine urine.
Findings of the Study
- The study concluded that concentrations under 315ng/mL of 3-hydroxylidocaine in a post-race urine sample is unlikely to be a result of recent use of Lidocaine as a local anesthetic.
- The study highlights that the research methodology utilized is unique, suggesting that other laboratories conducting similar studies but using differing methods may yield different results or amounts of detected 3-hydroxylidocaine in the urine samples.
Significance of Study
- The research provides useful insights for industry regulators in evaluating the significance of small concentrations of lidocaine or its metabolites in post-race urine samples.
- It clarifies the maximum Lidocaine dosage that does not alter the horse’s performance, assisting in assessing if Lidocaine was used illicitly for performance-enhancing purposes.
Cite This Article
APA
Harkins JD, Mundy GD, Woods WE, Lehner A, Karpiesiuk W, Rees WA, Dirikolu L, Bass S, Carter WG, Boyles J, Tobin T.
(1999).
Lidocaine in the horse: its pharmacological effects and their relationship to analytical findings.
J Vet Pharmacol Ther, 21(6), 462-476.
https://doi.org/10.1046/j.1365-2885.1998.00165.x Publication
Researcher Affiliations
- Maxwell H. Gluck Equine Research Center and the Department of Veterinary Science, University of Kentucky, Lexington 40506-0099, USA.
MeSH Terms
- Anesthetics, Local / administration & dosage
- Anesthetics, Local / pharmacokinetics
- Animals
- Chromatography
- Dose-Response Relationship, Drug
- Enzyme-Linked Immunosorbent Assay / standards
- Enzyme-Linked Immunosorbent Assay / veterinary
- Female
- Gas Chromatography-Mass Spectrometry
- Horses / blood
- Horses / metabolism
- Horses / urine
- Injections, Subcutaneous / veterinary
- Lidocaine / administration & dosage
- Lidocaine / analogs & derivatives
- Lidocaine / chemistry
- Lidocaine / pharmacokinetics
- Random Allocation
- Reproducibility of Results
Citations
This article has been cited 3 times.- de Oliveira MGC, Luna SPL, Nunes TL, Firmino PR, de Lima AGA, Ferreira J, Trindade PHE, Júnior RAB, de Paula VV. Post-operative pain behaviour associated with surgical castration in donkeys (Equus asinus). Equine Vet J 2021 Mar;53(2):261-266.
- Harkins JD, Karpiesiuk W, Tobin T, Dirikolu L, Lehner AF. Identification of hydroxyropivacaine glucuronide in equine urine by ESI+/MS/MS. Can J Vet Res 2000 Jul;64(3):178-83.
- Knych HK, Katzman S, McKemie DS, Arthur RM, Blea J. Pharmacokinetics and metabolism of lidocaine HCl 2% with epinephrine in horses following a palmar digital nerve block. BMC Vet Res 2023 Oct 30;19(1):225.
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