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Equine veterinary journal2009; 41(4); 361-365; doi: 10.2746/042516409x370900

Pharmacokinetics of detomidine and its metabolites following intravenous and intramuscular administration in horses.

Abstract: Detomidine is commonly used i.v. for sedation and analgesia in horses, but the pharmacokinetics and metabolism of this drug have not been well described. Objective: To describe the pharmacokinetics of detomidine and its metabolites, 3-hydroxy-detomidine (OH-detomidine) and detomidine 3-carboxylic acid (COOH-detomidine), after i.v. and i.m. administration of a single dose to horses. Methods: Eight horses were used in a balanced crossover design study. In Phase 1, 4 horses received a single dose of i.v. detomidine, administered 30 microg/kg bwt and 4 a single dose i.m. 30 microg/kg bwt. In Phase 2, treatments were reversed. Plasma detomidine, OH-detomidine and COOH-detomidine were measured at predetermined time points using liquid chromatography-mass spectrometry. Results: Following i.v. administration, detomidine was distributed rapidly and eliminated with a half-life (t1/2(el)) of approximately 30 min. Following i.m. administration, detomidine was distributed and eliminated with t1/2(el) of approximately one hour. Following, i.v. administration, detomidine clearance had a mean, median and range of 12.41, 11.66 and 10.10-18.37 ml/min/kg bwt, respectively. Detomidine had a volume of distribution with the mean, median and range for i.v. administration of 470, 478 and 215-687 ml/kg bwt, respectively. OH-detomidine was detected sooner than COOH-detomidine; however, COOH-detomidine had a much greater area under the curve. Conclusions: These pharmacokinetic parameters provide information necessary for determination of peak plasma concentrations and clearance of detomidine in mature horses. The results suggest that, when a longer duration of plasma concentration is warranted, the i.m. route should be considered.
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Publication Date: 2009-07-01 PubMed ID: 19562897DOI: 10.2746/042516409x370900Google Scholar: Lookup
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  • Controlled Clinical Trial
  • 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.

This study investigated the metabolism and pharmacokinetics of detomidine, a drug used for sedation and pain relief in horses, following administraton through injection into either a muscle (intramuscular) or a vein (intravenous).

Overview of the Study

  • The study was designed to enhance understanding of how detomidine and its metabolic products, 3-hydroxy-detomidine (OH-detomidine) and detomidine 3-carboxylic acid (COOH-detomidine), react in horse bodies depending on the method of administration.
  • A balanced crossover design was used with eight horses participating in the study; first four horses were given the drug intravenously and the other four intramuscularly, after which the methods of administration were switched.
  • The dose was the same for both administration methods, 30 micrograms per kilogram of body weight.
  • Plasma levels of detomidine, OH-detomidine, and COOH-detomidine were measured at set intervals using liquid chromatography-mass spectrometry, allowing for assessment of how the drug was processed by the horse’s body.

Study Findings

  • The drug was distributed rapidly in the body following intravenous administration, with a clearance half-life (amount of time required for the drug concentration to decrease by half in the body) of roughly 30 minutes.
  • The drug was distributed and cleared from the body more slowly after intramuscular injection, with a clearance half-life of approximately one hour. This suggests the drug’s effect would last longer with this administration method.
  • The rates of clearance and distribution volumes varied amongst individual subjects but average values were reported. Notably, OH detomidine appeared in blood sooner than COOH-detomidine; however, COOH-detomidine had a larger total exposure as it remained accessible in the system for an extended period.

Conclusions

  • This investigation provided valuable insights into how the drug detomidine behaves in the bodies of mature horses, including the rates at which it is distributed and cleared, and when its metabolic by-products appear in the bloodstream.
  • The results suggest intramuscular injection might be the preferred method when a prolonged effect of the drug is required.

Cite This Article

APA
Grimsrud KN, Mama KR, Thomasy SM, Stanley SD. (2009). Pharmacokinetics of detomidine and its metabolites following intravenous and intramuscular administration in horses. Equine Vet J, 41(4), 361-365. https://doi.org/10.2746/042516409x370900

Publication

Equine veterinary journal
ISSN: 0425-1644
NlmUniqueID: 0173320
Country: United States
Language: English
Volume: 41
Issue: 4
Pages: 361-365

Researcher Affiliations

Grimsrud, K N
  • K.L. Maddy Equine Analytical Chemistry Laboratory, California Animal Health and Food Safety Laboratory, School of Veterinary Medicine, University of California, Davis, California 95616, USA.
Mama, K R
    Thomasy, S M
      Stanley, S D

        MeSH Terms

        • Animals
        • Area Under Curve
        • Cross-Over Studies
        • Half-Life
        • Horses / metabolism
        • Hypnotics and Sedatives / administration & dosage
        • Hypnotics and Sedatives / blood
        • Hypnotics and Sedatives / metabolism
        • Hypnotics and Sedatives / pharmacokinetics
        • Imidazoles / administration & dosage
        • Imidazoles / blood
        • Imidazoles / metabolism
        • Imidazoles / pharmacokinetics
        • Injections, Intramuscular
        • Injections, Intravenous

        Citations

        This article has been cited 5 times.
        1. Rabbogliatti V, Amari M, Brioschi FA, Di Cesare F, Zani DD, De Zani D, Di Giancamillo M, Cagnardi P, Ravasio G. Use of dexmedetomidine repeated subcutaneous administration for balanced anaesthesia in horses. BMC Vet Res 2022 Jul 11;18(1):269.
          doi: 10.1186/s12917-022-03350-0pubmed: 35818051google scholar: lookup
        2. Romagnoli N, Al-Qudah KM, Armorini S, Lambertini C, Zaghini A, Spadari A, Roncada P. Pharmacokinetic profile and partitioning in red blood cells of romifidine after single intravenous administration in the horse. Vet Med Sci 2017 Nov;3(4):187-197.
          doi: 10.1002/vms3.70pubmed: 29152313google scholar: lookup
        3. Grimsrud KN, Ait-Oudhia S, Durbin-Johnson BP, Rocke DM, Mama KR, Rezende ML, Stanley SD, Jusko WJ. Pharmacokinetic and pharmacodynamic analysis comparing diverse effects of detomidine, medetomidine, and dexmedetomidine in the horse: a population analysis. J Vet Pharmacol Ther 2015 Feb;38(1):24-34.
          doi: 10.1111/jvp.12139pubmed: 25073816google scholar: lookup
        4. Thorn CA, Wilson DV, Wang S, Horne WA. Impact of sequential administration of detomidine, butorphanol, and midazolam on sedation, ataxia, stimulus response, and bispectral index in horses. Front Vet Sci 2025;12:1691137.
          doi: 10.3389/fvets.2025.1691137pubmed: 41200548google scholar: lookup
        5. Gomes ÉR, Felix LA, Gonzaga LWF, da Silva NFD, Soares BCF, de Almeida JVFC, Souza GP, Pereira RN, Taffarel MO, Ferrante M. Sedative effects of detomidine and midazolam combination in horses. Open Vet J 2025;15(7):2938-2947.
          doi: 10.5455/OVJ.2025.v15.i7.5pubmed: 41036345google scholar: lookup
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