AUTHOR=Ebner Lisa , O Odette , Simon Bradley , Lizarraga Ignacio , Smith Joe , Cox Sherry 

TITLE=Pharmacokinetics of butorphanol following intravenous and intramuscular administration in donkeys: A preliminary study

JOURNAL=Frontiers in Veterinary Science

VOLUME=9

YEAR=2022

URL=https://www.frontiersin.org/journals/veterinary-science/articles/10.3389/fvets.2022.979794

DOI=10.3389/fvets.2022.979794

ISSN=2297-1769

ABSTRACT=<p>The pharmacokinetics of butorphanol after intravenous (IVB) and intramuscular (IMB) administration in donkeys were determined in this preliminary study. Healthy male gelded donkeys (<italic>n</italic> = 5), aged 6–12 years old, were administered 0.1 mg/kg butorphanol IV or IM in a randomized, crossover design. Blood samples were obtained at predetermined intervals for 24 h (IVB) and 48 h (IMB) after administration. Plasma butorphanol concentrations were determined by high performance liquid chromatography and pharmacokinetic parameters were calculated. Following IVB administration, mean (± SE) apparent volume of distribution, elimination half-life, total body clearance, and area under the plasma concentration time curve from time 0 to infinity (AUC<sub>0−∞</sub>) were 322 ± 50 mL/kg, 0.83 ± 0.318 h, 400 ± 114 mL/h/kg, 370 ± 131 h·ng/mL, respectively. After IMB administration, a maximum plasma drug concentration of 369 ± 190 ng/mL was reached at 0.48 ± 0.09 h. The IMB AUC<sub>0−∞</sub> was 410 ± 60 h·ng/mL. Bioavailability of IMB was 133 ± 45%. The pharmacokinetics of butorphanol in healthy donkeys was characterized by faster elimination half-life compared to values from the equine literature.</p>