Pharmacokinetics of nalbuphine administered intravenously and subcutaneously in goats (Capra aegagrus hircus)

The purpose of this study was to evaluate the pharmacokinetics (PK) of intravenously (IV) and subcutaneously (SC) administered nalbuphine in domestic goats. Nalbuphine hydrochloride was administered at 0.8 mg/kg for both IV and SC routes in six goats with a minimum of 10-day washout period between sample collection phases. Eighteen plasma samples were collected over a 36-hour period, analyzed using reverse phase high-performance liquid chromatography (HPLC). Plasma data were analyzed using compartmental and noncompartmental approaches. Following IV nalbuphine administration, elimination half-life, area under the plasma concentration time curve from time 0 to infinity (AUC0 − ∞), concentration at time zero (C₀), and total body clearance were 120.4 ± 39.1 (min⁻¹ ± SD), 17311.01 ± 7227.32 (min·ng·mL⁻¹ ± SD), 675.6 ± 337.13 (ng·mL⁻¹ ± SD), and 44.5 ± 13.8 (mL·min⁻¹·kg⁻¹ ± SD), respectively. After SC nalbuphine administration, elimination half-life, area under the plasma concentration time curve from time 0 to infinity (AUC0 − ∞), and maximum plasma drug concentration were 129 ± 52.9 (min⁻¹ ± SD), 20826.5 ± 14376.2 (min·ng·mL⁻¹), and 368.03 ± 503.78 (ng·mL⁻¹). Calculated bioavailability for the SC route was 138 ± 126 (% ± SD). Nalbuphine in goats is characterized by rapid elimination and high subcutaneous bioavailability and may be a safe analgesic opioid option in goats in the future.