Determination of synovial fluid and serum concentrations, and morphologic effects of intraarticular ceftiofur sodium in horses.
Authors: Mills M L, Rush B R, St Jean G, Gaughan E M, Mosier D, Gibson E, Freeman L
Journal: Veterinary surgery : VS
Summary
# Intra-articular Ceftiofur Sodium in Equine Joints: Pharmacokinetics and Safety Mills and colleagues investigated whether direct joint injection of ceftiofur sodium could achieve therapeutic antimicrobial concentrations in equine synovial fluid whilst avoiding tissue damage, comparing this approach against intravenous administration in six healthy horses. Following intra-articular injection of 150 mg, peak synovial concentrations reached 5825 μg/mL within 15 minutes with a half-life of 5.1 hours, substantially exceeding the drug's MIC₉₀ throughout the 24-hour observation period; by contrast, intravenous administration (2.2 mg/kg) achieved only 7.31 μg/mL peak concentration and remained above MIC for less than 8 hours. Crucially, cytological examination revealed no inflammatory response to the intra-articular injection—white blood cell counts remained below 3,400 cells/μL and were indistinguishable from saline controls—whilst histopathological assessment detected no cartilage or synovial damage in treated joints. These findings suggest intra-articular ceftiofur represents a viable option for managing septic arthritis, offering superior local drug penetration with sustained therapeutic levels and an acceptable safety profile, though clinical efficacy in naturally infected joints warrants further investigation.
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Practical Takeaways
- •Intraarticular ceftiofur sodium is a safe and effective broad-spectrum option for treating septic arthritis, achieving therapeutic concentrations that persist throughout 24 hours
- •IA administration achieves 800-fold higher joint fluid concentrations than IV dosing while maintaining safety with no cartilage or synovial damage at the 150 mg dose
- •This dosing regimen may allow for once-daily or less frequent IA injections compared to other antibiotics, improving clinical practicality in managing septic joints
Key Findings
- •Intraarticular ceftiofur sodium achieved peak synovial fluid concentrations of 5825.08 µg/mL at 15 minutes, 795-fold higher than IV administration (7.31 µg/mL at 4 hours)
- •Synovial fluid ceftiofur concentrations remained above MIC90 for 24 hours after IA administration, compared to only 8 hours after IV administration
- •Intraarticular ceftiofur sodium (150 mg) produced no cytologic, histopathologic, or morphologic damage to cartilage or synovium with synovial half-life of 5.1 hours
- •White blood cell counts remained ≤3,400 cells/mL and synovial pH remained normal (7.32) after IA ceftiofur administration, indicating excellent local tolerability