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Journal of veterinary emergency and critical care (San Antonio, Tex. : 2001)2020; 31(3); 323-330; doi: 10.1111/vec.13035

Gentamicin plasma concentrations in hospitalized horses and retrospective minimal inhibitory concentrations of gram-negative equine pathogens.

Abstract: The optimal dosage regimen of gentamicin in horses is still under investigation. The objectives of this study were to determine gentamicin plasma concentrations in hospitalized horses treated with 10 mg/kg gentamicin (IV, q 24 h) and to determine whether a plasma concentration to minimum inhibitory concentration (MIC) ratio of 10:1 is reached for equine pathogens using this dose. Methods: Prospective clinical observational study; retrospective study on MICs of 131 gram-negative bacteria isolated from horses (2012-2015). Methods: University teaching hospital. Methods: Ninety-eight horses >6 months old, treated with gentamicin for their primary disease, consecutive samples. Results: Plasma concentrations were measured 1 hour (C ) and 20 hours (C ) after gentamicin administration using fluorescence polarization. Presence of systemic inflammatory response syndrome (SIRS) and azotemia was recorded, as well as the reason for antimicrobial administration (primary disease) and whether administration was prophylactic or therapeutic. The target C of ≥20 µg/mL gentamicin was reached in 90% of horses and was sufficient to reach a plasma concentration:MIC of 10:1 in 32 of 131 (24%) of gram-negative aerobic bacteria. A C ≤ 2 µg/mL was reached in 97% horses. Therapeutic versus prophylactic administration, primary disease, azotemia, and systemic inflammatory response syndrome were not associated with a failure to reach a desired peak or trough. Conclusions: The gentamicin dose of 10 mg/kg every 24 hours should be further investigated and safety assessed because a target gentamicin plasma concentration of ≥20 µg/mL was achieved in the majority of cases. Nephrotoxic side effects were not assessed. Individual drug monitoring should be performed because clinical factors are unreliable predictors of plasma concentrations. A gentamicin target concentration of ≥40 µg/mL does not offer additional benefits compared to ≥20 µg/mL, due to the bimodal distribution of resistance in bacterial isolates.
© Veterinary Emergency and Critical Care Society 2020.
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Publication Date: 2020-12-04 PubMed ID: 33274835DOI: 10.1111/vec.13035Google Scholar: Lookup
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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 study examines the effectiveness of a gentamicin dosage regimen in horses, determines the appropriate plasma concentration, and assesses the drug’s ability to inhibit common equine pathogens. The findings suggest that the majority of the horses achieved the target plasma concentration with the given dose, but further investigation and safety assessments were recommended.

Research Objectives

The research was conducted with the aim of determining:

  • The plasma concentrations of gentamicin (administered intravenously at a dose of 10mg/kg every 24 hours) in horses that were hospitalized.
  • Whether the plasma concentration to minimum inhibitory concentration (MIC) ratio of 10:1 was reached for equine pathogens with the administered dose.

Methods

This study involved two methods:

  • The observational study of horses who were treated with gentamicin for their primary disease in a university teaching hospital.
  • A retrospective study of the minimum inhibitory concentrations of 131 gram-negative bacteria that were isolated from horses from 2012 to 2015.

Results

The study found that:

  • The target plasma concentration of ≥20 µg/mL of gentamicin was reached in 90% of the horses.
  • The gentamicin was only effective at a plasma concentration:MIC of 10:1 in 24% (32 out of 131) of gram-negative aerobic bacteria.
  • Factors such as primary disease, azotemia, system inflammatory response, therapeutic versus prophylactic administration had no association with failure to achieve the desired peak or trough.

Conclusions

From the study, it was concluded that:

  • The gentamicin dose of 10 mg/kg every 24 hours should be further investigated and safety assessed, despite the majority of horses reaching the target concentration with this dose.
  • Individual drug monitoring should be performed due to unreliable clinical predictors of plasma concentrations.
  • Increasing the gentamicin concentration to ≥40 µg/mL offers no additional benefits compared to a target concentration of ≥20 µg/mL due to the bimodal distribution of resistance in bacterial isolates.

Importantly, the study did not assess potential nephrotoxic side effects of gentamicin, indicating a need for further research in this area.

Cite This Article

APA
Schoster A, Amsler M, Kirchgaessner C, Saleh L, Schwarzwald C, Schmitt S. (2020). Gentamicin plasma concentrations in hospitalized horses and retrospective minimal inhibitory concentrations of gram-negative equine pathogens. J Vet Emerg Crit Care (San Antonio), 31(3), 323-330. https://doi.org/10.1111/vec.13035

Publication

Journal of veterinary emergency and critical care (San Antonio, Tex. : 2001)
ISSN: 1476-4431
NlmUniqueID: 101152804
Country: United States
Language: English
Volume: 31
Issue: 3
Pages: 323-330

Researcher Affiliations

Schoster, Angelika
  • Vetsuisse Faculty, Equine Department, Clinic for Equine Internal Medicine, University of Zurich, Zurich, Switzerland.
Amsler, Morena
  • Vetsuisse Faculty, Equine Department, Clinic for Equine Internal Medicine, University of Zurich, Zurich, Switzerland.
Kirchgaessner, Constanze
  • Vetsuisse Faculty, Institute of Veterinary Bacteriology, University of Zurich, Zurich, Switzerland.
Saleh, Lanja
  • University Hospital, Institute for Clinical Chemistry, University of Zurich, Zurich, Switzerland.
Schwarzwald, Colin
  • Vetsuisse Faculty, Equine Department, Clinic for Equine Internal Medicine, University of Zurich, Zurich, Switzerland.
Schmitt, Sarah
  • Vetsuisse Faculty, Institute of Veterinary Bacteriology, University of Zurich, Zurich, Switzerland.

MeSH Terms

  • Animals
  • Anti-Bacterial Agents / blood
  • Drug Resistance, Bacterial
  • Gentamicins / blood
  • Gram-Negative Bacteria / drug effects
  • Horses
  • Microbial Sensitivity Tests
  • Prospective Studies
  • Retrospective Studies

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This article includes 26 references
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Citations

This article has been cited 6 times.
  1. van Spijk JN, Beckmann K, Wehrli Eser M, Stirn M, Steuer AE, Saleh L, Schoster A. Preliminary Investigation of Side Effects of Polymyxin B Administration in Hospitalized Horses. Antibiotics (Basel) 2023 May 5;12(5).
    doi: 10.3390/antibiotics12050854pubmed: 37237756google scholar: lookup
  2. Tyrnenopoulou P, Fthenakis GC. Clinical Aspects of Bacterial Distribution and Antibiotic Resistance in the Reproductive System of Equids. Antibiotics (Basel) 2023 Mar 28;12(4).
    doi: 10.3390/antibiotics12040664pubmed: 37107026google scholar: lookup
  3. van Spijk JN, Beckmann K, Wehrli Eser M, Boxler M, Stirn M, Rhyner T, Kaelin D, Saleh L, Schoster A. Adverse effects of polymyxin B administration to healthy horses. J Vet Intern Med 2022 Jul;36(4):1525-1534.
    doi: 10.1111/jvim.16470pubmed: 35801274google scholar: lookup
  4. Aleman MR, True A, Scalco R, Crowe CM, Costa LRR, Chigerwe M. Gentamicin-induced sensorineural auditory loss in healthy adult horses. J Vet Intern Med 2021 Sep;35(5):2486-2494.
    doi: 10.1111/jvim.16221pubmed: 34322916google scholar: lookup
  5. Guillot M, Mespoulhes-Rivière C, Bousquet-Mélou A, Lacroix MZ, Roques BB, Lallemand EA. Pharmacokinetics, pharmacodynamics, and local tolerance at injection site of penicillin and gentamicin administered by intravenous regional limb perfusion in standing horses: comparison between weightbearing and flexed limbs. BMC Vet Res 2025 Nov 7;21(1):650.
    doi: 10.1186/s12917-025-04936-0pubmed: 41204239google scholar: lookup
  6. Loppnow Z, Kersh K, Wang C, Spaethe S, Troy J. Clinical use of antimicrobial regional limb perfusion in adult horses diagnosed with synovial sepsis or penetrating synovial wounds at a single equine referral hospital in the Midwest United States-163 cases (2010-2020). Front Vet Sci 2025;12:1504486.
    doi: 10.3389/fvets.2025.1504486pubmed: 40206250google scholar: lookup
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