# Pharmacokinetics of neomycin in plasma, urine, and feces of donkeys (Equus asinus) after a single intragastric administration

## TL;DR

This study examines how neomycin is absorbed and eliminated in donkeys after a single dose, finding it is mainly excreted through feces with low systemic absorption.

## Contribution

The study provides novel pharmacokinetic data for neomycin in donkeys, supporting its use for local intestinal therapy.

## Key findings

- Neomycin is rapidly absorbed in donkey plasma with a Tmax of 0.85 h and Cmax of 4.05 μg·mL−1.
- Fecal excretion accounts for 70.99% of the administered dose, indicating low systemic absorption.
- The elimination half-life is 32.14 h, suggesting slow elimination and potential toxicity risks if used systemically.

## Abstract

Neomycin is an aminoglycoside antibiotic widely used in veterinary medicine for the treatment of gastrointestinal infections. However, pharmacokinetic studies of neomycin in donkeys are limited. The present study aimed to investigate the pharmacokinetic profiles of neomycin in donkey plasma, urine, and feces following a single intragastric administration, and to evaluate its suitability for clinical use in donkeys. A total of five healthy male donkeys with similar body weights were selected and administered a single dose of 30 mg·kg−1 body weight (BW) neomycin by gavage. The concentrations of neomycin in plasma, urine, and feces were determined. The results showed that neomycin was rapidly absorbed in donkeys, with a Tmax of 0.85 ± 0.36 h and a Cmax of 4.05 ± 1.99 μg·mL−1 in plasma. The elimination half-life (T₁/₂λ) was 32.14 ± 12.71 h, indicating a slow elimination rate. The cumulative excretion of neomycin in urine accounted for 15.08% of the administered dose, while fecal excretion accounted for 70.99%, suggesting low systemic absorption following intragastric administration. In conclusion, the low systemic absorption and high fecal excretion of intragastric neomycin in donkeys justify its use for intestinal infections. Given the prolonged elimination half-life of the absorbed drug, its use should be restricted to local intestinal therapy to minimize systemic exposure and toxicity risks. This study contributes to the advancement of precision medicine in donkey internal medicine, offering an evidence-based foundation for optimizing therapeutic strategies and minimizing systemic risks in donkeys.