Pharmacokinetics of Chloramphenicol and Chloramphenicol Glucuronide in Horses Following Administration Per Rectum or via Nasogastric Intubation.
Abstract: Chloramphenicol is a broad-spectrum antibiotic used in equine practice. It is known to produce adverse effects of hyporexia/anorexia after oral administration. Administration per rectum (PR) could mitigate the appetite suppression seen with oral administration and allow its use in horses unable to receive oral medications. The objectives of this study were to evaluate the relative bioavailability of chloramphenicol administered PR or via nasogastric tube (NGT) and determine relevant pharmacokinetic/pharmacodynamic parameters and metabolic ratios. Ten healthy, adult horses were administered chloramphenicol tablets (50 mg/kg) PR or via NGT in a randomized crossover design with a washout period. Blood samples were collected at predetermined times over 24 h, and plasma concentrations of chloramphenicol and its inactive metabolite chloramphenicol glucuronide were analyzed using a validated UPLC-MS/MS assay. Chloramphenicol tablets dissolved in water were rapidly metabolized to chloramphenicol glucuronide following both routes. Maximum concentrations for PR and NGT administration were (C; μg/mL) 0.119 ± 0.135 and 11.7 ± 5.8, respectively. Administration PR resulted in a relative bioavailability of 0.56% ± 0.86%. The metabolic ratio of chloramphenicol glucuronide to chloramphenicol was 20.2 ± 6.19 for PR and 5 ± 1.88 for NGT. Administration of chloramphenicol PR does not reach therapeutic concentrations nor prevent significant metabolism of chloramphenicol. After administration by NGT, plasma concentrations of chloramphenicol exceeded 2 μg/mL for 3.93 ± 0.44 h.
© 2025 John Wiley & Sons Ltd.
Publication Date: 2025-05-26 PubMed ID: 40418193DOI: 10.1111/jvp.13520Google Scholar: Lookup
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Summary
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The study seeks to analyze the effects of Chloramphenicol, a broad-spectrum antibiotic, when administered to horses through rectum or nasogastric tube, and measure how these methods of administration impact the metabolic ratio of the drug and its effectiveness.
Study Overview
- The study aimed to investigate how the different modes of administering chloramphenicol to horses, per rectum (PR) or via a nasogastric tube (NGT), affect its bioavailability and metabolism.
- The desire for an alternative administration route stems from the appetite-suppressing side effects associated with the oral intake of this medication.
- By comparing these two methods in healthy adult horses, researchers hoped to ascertain the most effective delivery method and related pharmacokinetic/pharmacodynamic parameters and metabolic ratios.
Research Methodology
- Ten healthy adult horses were chosen for the study.
- The horses were administered 50 mg/kg of chloramphenicol tablets either per rectum or via nasogastric tube based on a random crossover design with a washout period.
- After administration, blood samples were collected at preselected intervals over a 24-hour period.
- The samples were analyzed using a validated UPLC-MS/MS assay to measure the concentrations of chloramphenicol and its inactive metabolite chloramphenicol glucuronide.
Results and Conclusions
- The study found that chloramphenicol metabolized quickly into chloramphenicol glucuronide regardless of the administration method.
- However, there was a significant difference in the concentration levels of chloramphenicol between the two methods. PR administration resulted in a much lower concentration (C; μg/mL) of 0.119 ± 0.135, compared to NGT administration which resulted in a concentration of 11.7 ± 5.8.
- Overall, PR administration resulted in a relative bioavailability of only 0.56% ± 0.86%.
- The metabolic ratio between chloramphenicol glucuronide and chloramphenicol was also affected by the administration method. For PR it was 20.2 ± 6.19 compared to only 5 ± 1.88 for NGT.
- Therefore, the study concluded that PR administration was not an effective method since it did not reach therapeutic concentrations and did not prevent significant metabolism of chloramphenicol.
- After administration through NGT, plasma concentrations of chloramphenicol exceeded 2 μg/mL for 3.93 ± 0.44 h, demonstrating this to be the more effective administration method.
Cite This Article
APA
Sayler B, Manship AJ, Davis J, Taylor J, Gilliam L.
(2025).
Pharmacokinetics of Chloramphenicol and Chloramphenicol Glucuronide in Horses Following Administration Per Rectum or via Nasogastric Intubation.
J Vet Pharmacol Ther.
https://doi.org/10.1111/jvp.13520 Publication
Researcher Affiliations
- Department of Veterinary Clinical Sciences, Oklahoma State University Center for Veterinary Health Sciences, Stillwater, Oklahoma, USA.
- Department of Veterinary Clinical Sciences, Oklahoma State University Center for Veterinary Health Sciences, Stillwater, Oklahoma, USA.
- Department of Biomedical Sciences and Pathobiology, Virginia -Maryland College of Veterinary Medicine, Virginia, USA.
- Department of Pathobiology, Oklahoma State University College of Veterinary Medicine, Stillwater, Oklahoma, USA.
- Department of Veterinary Clinical Sciences, Oklahoma State University Center for Veterinary Health Sciences, Stillwater, Oklahoma, USA.
Grant Funding
- 5-556923 / Oklahoma State University Foundation Equine Research Fund
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