Morphine synovial fluid concentrations after intravenous regional limb perfusion in horses during standing sedation.
Authors: Kilcoyne Isabelle, Nieto Jorge, Nottle Bridget F, Flynn Harriet, Knych Heather K
Journal: Equine veterinary journal
Summary
# Morphine delivery via intravenous regional limb perfusion: achieving therapeutic synovial concentrations in standing horses Intravenous regional limb perfusion (IVRLP) offers a method to deliver high local drug concentrations to the distal limb whilst minimising systemic exposure—particularly valuable when treating painful infectious orthopaedic conditions requiring both analgesia and antimicrobial therapy. Kilcoyne and colleagues used a randomised crossover design in six horses to measure synovial fluid morphine concentrations from the radiocarpal joint following IVRLP with either morphine alone (0.1 mg/kg) or morphine combined with 2 g amikacin, collecting samples over 24 hours after tourniquet application. Measurable morphine concentrations appeared in all horses, with median peak synovial levels of 4753 ng/mL (M group) and 4477 ng/mL (MA group)—statistically equivalent between treatments—whilst concurrent amikacin achieved median peak concentrations of 323 μg/mL. For practitioners managing distal limb infections in standing sedated horses, this work demonstrates that morphine reaches therapeutic synovial concentrations via IVRLP without pharmacokinetic interference from amikacin, supporting its use as an analgesic adjunct that avoids systemic opioid side-effects. The small sample size (n=6) and lack of blinding warrant caution in extrapolating findings; nonetheless, the technical feasibility and achieved drug concentrations suggest IVRLP with morphine warrants further investigation as an evidence-based pain management strategy for distal limb orthopaedic disease.
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Practical Takeaways
- •Morphine can be effectively delivered to distal limb joints via IVRLP in standing sedated horses, offering a targeted analgesic approach for infectious orthopaedic conditions without systemic opioid effects.
- •Combining morphine with amikacin via IVRLP does not compromise morphine bioavailability, allowing dual therapeutic benefit in treating painful infectious conditions.
- •This technique may improve analgesia and outcomes in difficult-to-treat distal limb infections while avoiding the risks associated with systemic morphine administration.
Key Findings
- •Measurable morphine concentrations were achieved in synovial fluid of all horses following IVRLP, with median CMAX of 4753.1 ng/mL in the morphine-alone group and 4477 ng/mL in the morphine-amikacin group (p=0.5).
- •Concurrent amikacin administration did not significantly affect synovial morphine concentrations.
- •IVRLP with morphine is a feasible technique for delivering analgesia to distal limb joints while minimizing systemic side-effects.