Comparative analysis of some hematobiochemical and electrocardiographic changes following administration of medetomidine alone and combination with selected opioid agonists in Goats

Medetomidine is effective for sedation in small ruminants and is often combined with opioids to tailor depth and mitigate adverse effects. We conducted a randomized Latin-square crossover study in goats (n=۱۰) comparing five intravenous regimens: medetomidine ۲۰ µg/kg alone (MED) or combined with methadone ۰.۵ mg/kg (MME), morphine ۰.۵ mg/kg (MMO), tramadol ۵ mg/kg (MTR), or pethidine ۱ mg/kg (MPE). Drugs were administered via the left jugular vein over ۲ min. Blood was collected at ۰, ۱۲۰ min, and ۲۴ h for WBC, PCV, cardiac troponin I (cTnI), homocysteine (Hcy), and ALT/AST; bipolar-limb ECGs were recorded at ۰, ۵, and ۱۲۰ min. Baseline hematologic, biochemical, and ECG values did not differ across periods. cTnI remained within assay reference limits with no within-regimen change, although between-regimen differences appeared at ۱۲۰ min and ۲۴ h, with MED lower than methadone/tramadol at ۱۲۰ min and lower than pethidine/tramadol at ۲۴ h. Hcy showed no intergroup differences but increased modestly only with MED at ۲۴ h. Hematologic effects were regimen-specific: WBC decreased with MMO at ۲ h (p < ۰.۰۵), and PCV decreased with MTR at ۲–۲۴ h (p < ۰.۰۵). Hepatic enzymes showed no significant treatment or time effects. On ECG, PR and QT intervals lengthened over time (notably with MED and MMO), RR intervals generally prolonged consistent with bradycardia, and MPE increased T-wave amplitude (p < ۰.۰۵). Overall, medetomidine–opioid combinations produced distinct hematologic and ECG signatures without detectable within-regimen cTnI elevation. These data support individualized opioid selection with routine ECG monitoring when using medetomidine in goats.

Keywords:

Sedation , Mede­tomidine , Opioid ago­nists , Goats