Pharmacokinetics and selected behavioral responses to butorphanol and its metabolites in goats following intravenous and intramuscular administration

Immediate Postoperative Analgesia of Nalbuphine-Ketamine Combination Compared with Ketamine Alone in Xylazine-Sedated Goats Undergoing Left Flank Laparotomy

Goats have been used as animal models in research, and the need for achieving safer anesthesia for research or surgical intervention is gaining much attention. The objective of this study was to evaluate intraoperative effects and the immediate postoperative analgesia of nalbuphine–ketamine regimen in goats. Twenty clinically healthy adult female crossbred goats weighing 14 ± 2 kg were allocated randomly into each of two equally sized groups. All animals were sedated with intramuscular (IM) xylazine (0.07 mg/kg), then anesthesia was intravenously (IV) induced with ketamine alone (10 mg/kg) (XK group), or a combination of nalbuphine (0.5 mg/kg) and ketamine (5 mg/kg) (XNK group). Following induction, left flank laparotomy was performed and then sutured. The quality of anesthesia and immediate postoperative analgesia was evaluated. Immediate postoperative analgesia was assessed up to 5 h after standing, using a modified Unesp–Botucatu acute composite pain scale (USAPS). Serum cortisol, glucose, insulin, and C-reactive protein (CRP) were measured at ½, 1, 2, 4, 6, 12, and 24 h, postoperatively (PO). The USAPS pain scores were significantly lower in the XNK compared to the XK group (p < 0.05). The XNK group exhibited a statistically significant difference in the level of serum cortisol at ½ and 1 h PO (p = 0.018 and 0.045, respectively) compared to the XK group. At 2, 4, 6 h PO, CRP significantly decreased (p = 0.023, 0.040 and 0.005, respectively) in the XNK compared to the XK group. Nalbuphine–ketamine produced an acceptable induction of anesthesia and recovery compared to ketamine. Recovery with nalbuphine–ketamine was faster and better quality. The USAPS pain scores were lower in nalbuphine–ketamine, indicating that this novel combination produces better postoperative pain control than ketamine alone.

Physiological and Clinical Responses in Pigs in Relation to Plasma Concentrations during Anesthesia with Dexmedetomidine, Tiletamine, Zolazepam, and Butorphanol

Simple Summary

Reliable protocols are needed for short-term anesthesia in pigs. The study’s aim is to identify an anesthetic procedure that, without the use of sophisticated equipment, ensures an acceptable depth and length of anesthesia, a regular spontaneous breathing pattern, and a stable hemodynamic condition for the animal. A total of 12 pigs were given a single intramuscular injection of dexmedetomidine, tiletamine, zolazepam, and butorphanol. To investigate the possibility of prolonging the anesthesia, six of the pigs also received an intravenous dose of the drug combination after one hour. Physiological and clinical responses and drug plasma concentrations were examined. The main results suggest that intramuscular administration of the drug combination provides up to two hours of anesthesia with stable physiological parameters and an acceptable level of analgesia. An intravenous administration of one-third of the original dosage prolonged the anesthesia for another 30 min. Since the pigs were able to breathe spontaneously, none of them were intubated. The study also provides new information about each drug’s plasma concentrations and the impact of the drug combination in pigs. This technique can be used to perform nonsurgical operations or transports when short-term anesthesia is required.

Abstract

Reliable protocols for short-term anesthetics are essential to safeguard animal welfare during medical investigations. The aim of the study was to assess the adequacy and reliability of an anesthetic protocol and to evaluate physiological and clinical responses, in relation to the drug plasma concentrations, for pigs undergoing short-term anesthesia. A second aim was to see whether an intravenous dosage could prolong the anesthesia. The anesthesia was induced by an intramuscular injection of dexmedetomidine, tiletamine-zolazepam, and butorphanol in 12 pigs. In six of the pigs, a repeated injection intravenously of one-third of the initial dose was given after one hour. The physiological and clinical effects from induction to recovery were examined. Plasma concentrations of the drugs were analyzed and pharmacokinetic parameters were calculated. Each drug’s absorption and time to maximal concentration were rapid. All pigs were able to maintain spontaneous respiration. The route of administration did not alter the half-life of the drug. The results suggest that intramuscular administration of the four-drug combination provides up to two hours of anesthesia with stable physiological parameters and an acceptable level of analgesia while maintaining spontaneous respiration. A repeated intravenous injection may be used to extend the time of anesthesia by 30 min.

The effects of midazolam and butorphanol, administered alone or combined, on the dose and quality of anaesthetic induction with alfaxalone in goats

Goats are rarely anaesthetised; consequently, scant information is available on the efficacy of anaesthetic drugs in this species. Alfaxalone is a relatively new anaesthetic agent, of which the efficacy in goats has not yet been studied. In this study, the sedative and alfaxalonesparing effects of midazolam and butorphanol, administered alone or concomitantly, in goats were assessed. Eight clinically healthy goats, four does and four wethers, were enlisted in a randomised crossover manner to receive intramuscular sedative treatments consisting of saline 0.05 mL/kg, or midazolam 0.30 mg/kg, or butorphanol 0.10 mg/kg, or a combination ofmidazolam 0.30 mg/kg with butorphanol 0.10 mg/kg before intravenous induction of general anaesthesia with alfaxalone. Following induction, the goats were immediately intubated and the quality of anaesthesia and basic physiological cardiorespiratory and blood-gas parameters were assessed until the goats had recovered from anaesthesia. The degree of sedation, quality of induction and recovery were scored. When compared with saline (3.00 mg/kg), midazolam,administered alone or with butorphanol, caused a statistically significant increased level of sedation and a reduction in the amount of alfaxalone required for induction (2.00 mg/kg and 1.70 mg/kg, respectively). Butorphanol alone (2.30 mg/kg) did not cause significant changes in level of sedation or alfaxalone-induction dose. During induction and recovery, the goats were calm following all treatments, including the control group. Cardiorespiratory and blood gasparameters were maintained within clinically acceptable limits. The present study showed that midazolam, administered alone or combined with butorphanol, produces a degree of sedation that significantly reduces the dose of alfaxalone required for induction of general anaesthesia in goats, without causing any major adverse cardiorespiratory effects.

Pharmacokinetics and intramuscular bioavailability of a single dose of butorphanol in Asian elephants (Elephas maximus)

Captive Asian elephants (Elephas maximus) are susceptible to lameness resulting from foot and joint pain, including chronic arthritis. In the past, opioid analgesics, such as butorphanol, have been used clinically for pain management. However, dosages used in treating elephants were often extrapolated from data in horses, with no pharmacokinetic information on the specific agents used in elephant species. In this pharmacokinetic study, six adult captive Asian elephants (5 female, 1 male castrate) were administered a 0.015 mg/kg dose of butorphanol by both i.v. and i.m. routes. A complete crossover design was used with a 3-wk washout period between treatments. Serial blood samples were collected immediately prior to butorphanol administration and at 5, 10, 20, and 40 min and 1, 1.5, 2, 3, 4, 5, 6, 8, 10, and 24 h after administration. The butorphanol analysis was performed using a validated liquid chromatography-mass spectrophotometric assay with a limit of quantitation of 0.025 ng/ml. The mean Cmax after i.m. administration was 7.9 ng/ml, with a corresponding Tmax, of 40 min and t(1/3), of 7.1 h. After i.v. administration, the mean Vd(ss) was 1.4 L/kg and the mean Cl(p) was 0.26 L/kg/h. Mean i.m. bioavailability was 37%. The results indicate that butorphanol used at 0.015 mg/kg i.m. or i.v. could be useful in elephants when given for pain control.