Effects of age on the pharmacokinetics and selected pharmacodynamics of intravenously administered fentanyl in foals.
Abstract: The use of fentanyl is limited in adult horses, in part due to potential for central nervous system excitation. The pharmacokinetics and the plasma concentration-related behavioural actions of fentanyl have not been described for young foals. The goal of the present study was to describe the pharmacokinetics and behavioural effects of fentanyl following administration to the same group of foals at 3 different ages. Experimental study in healthy foals. Fentanyl was administered i.v. (4 μg/kg bwt) to a group of 9 foals on 3 separate occasions at 6–8, 20–22 and 41–42 days of age. Blood samples were collected prior to administration and at multiple times until 24 h post administration. Blood samples were analysed for fentanyl concentrations and pharmacokinetics determined at each age. Behavioural and physiological effects were also assessed. The average volume of distribution was 3.55, 1.53 and 1.82 l/kg bwt and clearance 50.2, 40.7 and 35.7 ml/min/kg bwt when foals were 6–8, 20–22 and 41–42 days of age, respectively. The elimination half-life was slightly prolonged (49.3 min) at 6–8 days relative to 20–22 and 41–42 days of age (25.8 and 33.7 min, respectively). The primary metabolite detected in blood samples was the same as for adult horses. While the onset and duration varied widely between foals, sedation was observed at all ages studied. Fentanyl appears to be consistently well tolerated following i.v. administration of 4 μg/kg bwt to foals ranging in age from 1 to 6 weeks. The results of this study support further study of fentanyl for clinical use in foals.
Publication Date: 2014-09-30 PubMed ID: 25263971DOI: 10.1111/evj.12246Google Scholar: Lookup
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- Clinical Trial
- Journal Article
- Research Support
- Non-U.S. Gov't
Summary
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The research focuses on understanding the effects of fentanyl, a type of analgesic, on foals at different ages, with the goal of determining the drug’s pharmacokinetics (how it moves within the body) and behavioral effects.
Overview of Research
- The study aimed to identify the effects of age on the pharmacokinetics and pharmacodynamics of intravenously administered fentanyl in foals (young horses). This will help to improve understanding on dosing in different age groups of horses.
- The research experimented on a group of nine healthy foals, administering the drug on three separate occasions when they were 6-8 days old, 20-22 days old, and 41-42 days old, respectively.
Procedure and Methodology
- For each of the horses, a dose was administered intravenously at a concentration of 4 μg/kg. Blood samples were then taken various times up until 24 hours after administration.
- Analysts then measured the fentanyl concentrations in these blood samples to identify the drug’s pharmacokinetics at each age.
- Alongside this, the researchers observed the foals for any behavioral changes or physiological effects.
Research Findings
- It was found that the average volume of distribution and clearance of the drug had differences across each age cluster. The 6–8 days olds had the highest volume of distribution at 3.55 l/kg body weight, compared to 1.53 and 1.82 l/kg for foals at 20–22 and 41–42 days respectively.
- Clearance rates were also recorded to be 50.2, 40.7 and 35.7 ml/min/kg for the 6–8, 20–22 and 41–42 day olds respectively.
- It had also been observed that the youngest set of foals had a slightly longer half-life of the drug within their bodies, with a half-life of 49.3 mins compared to 25.8 and 33.7 mins for the older foals.
- The primary metabolite was found to be the same as adult horses in these foals and behavioral changes such as sedation were observed, although the onset and duration varied, for all ages in the study.
Conclusion
- The foals in the study appeared to tolerate the fentanyl well at all ages studied.
- The researchers concluded that further studies into the clinical use of fentanyl in foals was warranted based on these findings.
Cite This Article
APA
Knych HK, Steffey EP, Mitchell MM, Casbeer HC.
(2014).
Effects of age on the pharmacokinetics and selected pharmacodynamics of intravenously administered fentanyl in foals.
Equine Vet J, 47(1), 72-77.
https://doi.org/10.1111/evj.12246 Publication
Researcher Affiliations
MeSH Terms
- Aging
- Analgesics, Opioid / blood
- Analgesics, Opioid / pharmacokinetics
- Animals
- Area Under Curve
- Female
- Fentanyl / blood
- Fentanyl / pharmacokinetics
- Half-Life
- Horses / blood
- Horses / metabolism
- Male
Citations
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