Pharmacokinetics of butorphanol and evaluation of physiologic and behavioral effects after intravenous and intramuscular administration to neonatal foals.

This research article focuses on studying the pharmacokinetics (drug’s behavior in the body), clinical effects, and safety of the drug butorphanol in neonatal foals (baby horses). The main findings include the fact that the drug behavior differs in baby horses compared to adult ones, and the prominent behavioural effects of drug administration were sedation and increased feeding behavior.

Study Objective

• The purpose of this study was to understand the pharmacokinetic behavior (how the drug gets absorbed, distributed, metabolized, and excreted) of butorphanol in baby horses when administered intravenously (IV) and intramuscularly (IM).
• The study also aimed to evaluate if administration of butorphanol results in any physiological or behavioral changes in neonatal foals.
• The research attempted to record any adverse effects associated with the use of butorphanol in neonatal foals.

Methodology

• The study, involving six healthy mixed-breed pony foals aged between 3 and 12 days, adopted a 3-way crossover design. In this type of design, each participant is tested under multiple conditions.
• The foals received butorphanol (both IV and IM, at 0.05 mg/kg) and IV saline (which served as a control group).
• The concentration of butorphanol was determined through high-performance liquid chromatography and then analyzed using a non-compartmental pharmacokinetic model.
• Vital signs were recorded at specific intervals post drug administration to track physiological responses.
• To assess activity, pedometers were used. Behavioral data was accumulated using a 2-hour real-time video recording.

Results

• Post IV injection of butorphanol, the terminal half-life of the drug was found to be around 2.1 hours, with an initial concentration (C0) of 33.2 +/- 12.1 ng/mL.
• For IM injection, the maximum concentration (Cmax) and the time taken to reach this concentration (Tmax) were 20.1 +/- 3.5 ng/mL and 5.9 +/- 2.1 minutes respectively.
• The bioavailability of butorphanol was calculated to be 66.1 +/- 11.9%.
• While the vital signs were minimally affected, the foals that received butorphanol spent significantly more time nursing than the control foals and showed signs of sedation.

Conclusions

• The researchers concluded that the disposition (the process of removing the drug from the body) of butorphanol in neonatal foals is different from that in adult horses.
• The main behavioral effects after butorphanol administration to neonatal foals were reported to be sedation and increased feeding behavior.