Pharmacokinetics of danofloxacin in horses after intravenous, intramuscular and intragastric administration.
Authors: Fernández-Varón E, Ayala I, Marín P, Carrión A, Martos N, Escudero E, Cárceles C M
Journal: Equine veterinary journal
Summary
# Editorial Summary: Danofloxacin Pharmacokinetics in Horses Danofloxacin, a fluoroquinolone antimicrobial developed for veterinary use, had never been formally characterised in equine patients despite showing excellent in vitro activity, prompting researchers to establish its pharmacokinetic profile across three administration routes. Using a crossover design in six healthy horses, the team administered 1.25 mg/kg danofloxacin intravenously, intramuscularly and via nasogastric tube, then tracked plasma concentrations by HPLC and monitored injection-site tolerability through creatine kinase activity. Intramuscular administration proved most clinically promising, achieving 88% bioavailability with peak plasma concentrations of 0.35 mg/l and a half-life of 5.36 hours—drug exposure levels consistent with therapeutic efficacy for many equine infections—whilst tolerability remained high despite transient threefold elevation in CK activity at 12 hours post-injection. By contrast, oral bioavailability was disappointing at only 22%, rendering the intragastric route unsuitable for clinical use. These findings support intravenous and intramuscular danofloxacin as viable options for treating susceptible bacterial infections in horses, with intramuscular dosing offering the practical advantage of needle administration whilst maintaining therapeutic drug concentrations.
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Practical Takeaways
- •Intramuscular danofloxacin is the preferred route for treating bacterial infections in horses due to reliable therapeutic levels and high bioavailability
- •Avoid intragastric administration via nasogastric tube as poor oral bioavailability makes it unreliable for clinical use
- •Mild muscle reaction at IM injection sites is expected but resolves within 72 hours and should not deter use of this effective antibiotic
Key Findings
- •Intramuscular danofloxacin achieved 88.48% bioavailability with therapeutic plasma concentrations suitable for treating equine infections
- •Intragastric administration showed poor bioavailability (22.36%) limiting clinical utility via nasogastric tube
- •Terminal half-lives were 6.31 h (IV), 5.36 h (IM), and 4.74 h (IG), supporting once or twice daily dosing intervals
- •Intramuscular injection caused only transient elevation in creatine kinase (3-fold at 12 h, normalized by 72 h) indicating good tolerability