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

To determine synovial concentrations of morphine after intravenous regional limb perfusion (IVRLP) with morphine or morphine in combination with gentamicin in clinically healthy, standing sedated horses.

Experimental.

Adult horses (n = 6).

IVRLP was performed using 0.1 mg/kg morphine (M) in standing sedated horses. After a 3-week washout period, IVRLP was performed on the same forelimb with a combination of 0.1 mg/kg morphine and 1 g gentamicin (M/G). Synovial fluid from the middle carpal joint of the perfused limb and jugular blood samples were collected immediately before each perfusion and 20 minutes, and 2, 8, and 24 hours after IVRLP. Morphine and gentamicin concentrations were determined by ELISA. Data were assessed using 2-way repeated measures ANOVA with significance set at P ≤ .05.

Synovial fluid morphine concentrations were greatest 20 minutes after perfusion. Mean ± SD peak synovial morphine concentrations over 12 perfusions were 3903 ± 4881 ng/mL. There was no significant difference in morphine synovial concentrations after M or M/G. Plasma morphine concentrations peaked within 2 hours of perfusion (range, 11-63 ng/mL). Mean peak gentamicin concentrations in synovial fluid were 76,315 ± 39,809 ng/mL. IVRLP morphine did not cause clinically apparent adverse effects.

IVRLP in standing sedated horses results in measurable levels of morphine in synovial fluid and synovial concentrations of gentamicin after perfusion in combination with morphine are equivalent to those previously reported.