Elution of antimicrobials from a cross-linked dextran gel: In vivo quantification.
Authors: Hart S K, Barrett J G, Brown J A, Papich M G, Powers B E, Sullins K E
Journal: Equine veterinary journal
Summary
# Editorial Summary Researchers investigated whether antimicrobial-impregnated cross-linked dextran gels could deliver therapeutic drug concentrations to infected tissues whilst minimising systemic absorption in horses. Using subcutaneous implants in 11 horses' necks, they measured interstitial fluid concentrations of amikacin, vancomycin, and clindamycin (individually and in combination) via capillary ultrafiltration probes placed at the implantation site and 1.5 cm away over a 10-day period. Peak antimicrobial concentrations were achieved within 4–8 hours depending on the drug, with vancomycin maintaining concentrations above minimum inhibitory thresholds for ≥10 days, amikacin for 9 days and clindamycin for 8 days—substantially longer than systemic dosing would provide—whilst plasma and serum levels remained negligible, demonstrating minimal systemic uptake. Histological examination revealed no significant adverse tissue reactions compared to control incisions, establishing the gel as both safe and effective. For equine practitioners managing localised infections (particularly deep wounds, bone infections or post-surgical complications), this delivery system offers prolonged therapeutic antimicrobial concentrations at the affected site without the complications of repeated systemic medication or the risks of systemic toxicity, making it a valuable alternative to conventional local or parenteral treatment protocols.
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Practical Takeaways
- •Cross-linked dextran gels provide sustained local antimicrobial delivery for 8-10+ days, offering an effective alternative to systemic therapy for localized infections
- •Minimal systemic absorption of medications suggests this delivery method is safe with low risk of drug-related side effects or toxicity
- •This local delivery approach maintains therapeutic antimicrobial concentrations at the infection site while avoiding the need for repeated injections or systemic administration
Key Findings
- •Maximum antimicrobial concentrations were detected at 4 h for amikacin and 8 h for vancomycin and clindamycin from combination gel
- •Antimicrobial concentrations remained above minimum inhibitory concentration for ≥10 days (vancomycin), 9 days (amikacin), and 8 days (clindamycin) at the implantation site
- •Systemic absorption was minimal with plasma/serum concentrations below detectable limits or very low (clindamycin 0.52-0.63 μg/ml)
- •Cross-linked dextran gel showed no significant adverse effects on wound healing histomorphology compared to control incisions