Pharmacokinetics of marbofloxacin in horses.
Authors: Bousquet-Melou A, Bernard S, Schneider M, Toutain P L
Journal: Equine veterinary journal
Summary
Marbofloxacin, a fluoroquinolone antibiotic with activity against gram-negative and selected gram-positive bacteria, required pharmacokinetic characterisation in horses to establish evidence-based dosing protocols. Bousquet-Melou and colleagues administered single 2 mg/kg doses via intravenous, subcutaneous, and oral routes to six horses, measuring drug clearance, bioavailability, and minimal inhibitory concentrations (MICs) against equine clinical isolates. The drug demonstrated excellent subcutaneous bioavailability (98%), moderate oral bioavailability (62%), and a prolonged terminal half-life of 756 hours, with clearance of 0.25 l/kg/h enabling once-daily dosing; however, efficacy modelling revealed that a standard 2 mg/kg/24 h regimen was adequate for enterobacterial infections (MIC₉₀ 0.027 µg/ml) but suboptimal for *Staphylococcus aureus* (MIC₉₀ 0.21 µg/ml). For practitioners, this work clarifies that marbofloxacin at 2 mg/kg daily suits gram-negative bacterial infections across all administration routes, whilst *S. aureus* infections may require dose escalation or alternative agents—critical guidance for infection-specific treatment planning in equine medicine.
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Practical Takeaways
- •Marbofloxacin at 2 mg/kg once daily is suitable for gram-negative infections (enterobacteriaceae) in horses but may be suboptimal for S. aureus, requiring alternative dosing or agent selection
- •Excellent subcutaneous bioavailability (98%) makes this route nearly equivalent to IV administration, offering flexibility for field treatment
- •The very long half-life (756 h) suggests potential for once-daily dosing, which improves compliance in equine practice
Key Findings
- •Marbofloxacin clearance in horses is 0.25 ± 0.05 l/kg/h with terminal half-life of 756 ± 199 h
- •Subcutaneous bioavailability is 98 ± 11% and oral bioavailability is 62 ± 8%
- •MIC90 values are 0.027 µg/ml for enterobacteriaceae and 0.21 µg/ml for Staphylococcus aureus
- •Dosage regimen of 2 mg/kg/24h is more appropriate for enterobacteriaceae than S. aureus infections based on efficacy indices