Morphine Synovial Fluid Concentrations After Intravenous Regional Limb Perfusion in Standing Horses.

The research article studies the concentration of morphine in the synovial fluid of horses after intravenous regional limb perfusion (IVRLP), either with only morphine or with gentamicin combined.

Objective & Methodology

The study aimed to find out the synovial concentrations of morphine in standing sedated horses after performing IVRLP. The research was experimental in nature and was conducted on six adult horses. The first IVRLP was performed using only morphine at a dosage of 0.1mg/kg. After a 3-week washout period, another perfusion was done on the same forelimb of each horse but this time using a combination of 0.1mg/kg of morphine and 1g of gentamicin (M/G).

• Synovial fluid (a fluid found in joints) was collected from the middle carpal joint of the perfused limb.
• Jugular blood samples were collected immediately before each perfusion and then at different intervals post IVRLP: 20 minutes, 2 hours, 8 hours and 24 hours.
• Concentrations of morphine and gentamicin in these samples were determined using ELISA (enzyme-linked immunosorbent assay) – a commonly used method for measuring amounts of proteins or other substances in a solution.

The data were statistically assessed using a 2-way repeated measures ANOVA.

Results & Conclusion

The results indicated that the concentration of morphine in the synovial fluid was highest 20 minutes after the perfusion, with a mean peak concentration of 3903 ± 4881ng/mL recorded over 12 perfusions. No significant difference in the concentration of morphine was observed whether administered alone or with gentamicin.

The plasma morphine concentration peaked within 2 hours of perfusion, with a range of 11-63ng/mL. Gentamicin, when used, had a mean peak synovial fluid concentration of 76,315 ± 39,809ng/mL.

There were no clinically notable adverse effects seen after the IVRLP of morphine. The research concluded that IVRLP in sedated standing horses yields measurable levels of morphine in the synovial fluid – even when used in combination with gentamicin, the results were very much in line with those reported previously.