Synovial Concentration of Trimethoprim-Sulphadiazine Following Regional Limb Perfusion in Standing Horses.
Authors: Gustafsson Kajsa, Tatz Amos J, Dahan Roee, Abu Ahmad Wiessam, Britzi Malka, Sutton Gila A, Kelmer Gal
Journal: Animals : an open access journal from MDPI
Summary
# Editorial Summary: Trimethoprim-Sulphadiazine via Regional Limb Perfusion in Horses Intravenous regional limb perfusion (IVRLP) is an attractive route for delivering high antibiotic concentrations directly to joint structures, but this investigation questioned whether trimethoprim-sulphadiazine (TMP-SDZ) achieves adequate synovial penetration when administered via cephalic vein perfusion with a 30-minute tourniquet application. Ten standing horses received 4 g TMP-SDZ diluted in saline, with synovial fluid and blood samples collected at intervals up to 24 hours, analysed using liquid chromatography/tandem mass spectrometry to determine whether drug concentrations remained above the established minimum inhibitory concentrations (0.5 µg/mL for trimethoprim, 9.5 µg/mL for sulphadiazine). Although peak synovial concentrations were substantial—36 ± 31.1 µg/mL trimethoprim and 275.3 ± 214.4 µg/mL sulphadiazine—drug levels declined precipitously, with none of the horses maintaining therapeutic concentrations by 12 hours post-perfusion. Most concerning was the adverse reaction profile: five of ten horses (50%) developed severe vasculitis accompanied by significant pain lasting up to seven days, substantially limiting this technique's clinical utility. These findings argue against cephalic IVRLP for TMP-SDZ delivery in septic synovitis cases, despite theoretically attractive pharmacokinetics, and suggest that alternative administration routes warrant exploration for horses requiring this antibiotic combination in joint infections.
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Practical Takeaways
- •Do not use intravenous regional limb perfusion with trimethoprim-sulphadiazine for septic joint treatment due to rapid decline in synovial drug levels below therapeutic thresholds within 12 hours
- •Be aware that cephalic vein IVRLP with this drug combination causes severe vasculitis and prolonged pain in approximately 50% of treated horses, creating significant welfare concerns
- •Consider alternative routes of antimicrobial administration (such as systemic IV, intra-articular injection, or other IVRLP agents) when treating septic synovitis with trimethoprim-sulphadiazine-sensitive bacteria
Key Findings
- •Peak synovial concentrations of trimethoprim (36 ± 31.1 µg/mL) and sulphadiazine (275.3 ± 214.4 µg/mL) were reached at 20 and 26.4 minutes respectively after IVRLP
- •Synovial concentrations fell below the minimum inhibitory concentration (0.5 and 9.5 µg/mL) by 12 hours post-injection in all horses
- •Severe vasculitis and pain lasting up to one week occurred in 5 out of 10 horses (50%) following cephalic vein IVRLP
- •IVRLP with trimethoprim-sulphadiazine is not recommended due to inadequate sustained synovial concentrations and significant adverse effects