A pharmacokinetic study of phenobarbital in mature horses after oral dosing.
Abstract: The pharmacokinetics of phenobarbital were determined in six mature horses after a single oral dose. Horses were administered a 5.5 mg/kg of body weight oral dose of phenobarbital tablets. Based on the combined evaluation of i.v. and oral results, phenobarbital displayed two-compartment pharmacokinetics in the horse with a terminal half-life of 19.0 +/- 4.4 (mean +/- SD) h. This half-life is considerably shorter than those reported for dogs and humans. The steady-state volume of distribution (Vdss/F) and the total body clearance (Clt/F) of phenobarbital were 0.753 +/- 0.115 l/kg and 27.9 +/- 9.2 ml/h/kg, respectively. The average extent of oral absorption was 101% with a range of 76 to 124% among the six horses. Examination of the absorption kinetics demonstrated a biphasic absorption process in four horses with a rapid absorption followed by a slower absorption phase. The mean residence time (MRT) was 36.9 +/- 4.1 h and the mean residence time for oral absorption (MRTabs) was 11.3 h. Based on the results of the present study, an oral dosing regimen of 11 mg/kg of body weight every 24 h can be recommended.
Publication Date: 1987-12-01 PubMed ID: 3437492DOI: 10.1111/j.1365-2885.1987.tb00103.xGoogle Scholar: Lookup
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- Journal Article
Summary
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The research study explores the pharmacokinetics of phenobarbital when administered orally to mature horses, revealing faster metabolization and clearance than in dogs and humans.
Objective and Methodology
- The objective of this study was to understand the pharmacokinetics or the movement of phenobarbital in the body of mature horses. This was done by administering a single oral dose of phenobarbital to six horses.
- The dosage provided was 5.5 mg/kg of body weight for each horse. The study then tracked the absorption, distribution, metabolism, and excretion of the drug.
Findings and Observations
- The researchers found that phenobarbital displayed two-compartment pharmacokinetics in the horses. This term refers to the drug’s distribution in two distinct phases: distribution and elimination.
- The terminal half-life of phenobarbital in horses was found to be 19.0 +/- 4.4 hours. This half-life is significantly shorter than those reported for dogs and humans, indicating that phenobarbital lasts less time in the system of a horse compared to those species.
- The steady-state volume of distribution (Vdss/F) was 0.753 +/- 0.115 l/kg. This refers to the theoretical volume that would be necessary to contain the total amount of an administered drug at the same concentration that it is observed in the blood plasma.
- The total body clearance (Clt/F) was 27.9 +/- 9.2 ml/h/kg. This term refers to the volume of plasma from which a substance is completely removed per unit time.
- The average extent of oral absorption was 101% with a range of 76 to 124% among the six horses. This implies that, on average, almost all the administered drug was absorbed by the body.
- An examination of the absorption kinetics showed a rapid absorption followed by a slower phase in four horses, indicating a biphasic absorption process.
Conclusion and Recommendation
- The mean residence time (MRT) in the horses was recorded as 36.9 +/- 4.1 hours and the mean residence time for oral absorption (MRTabs) was 11.3 hours. The MRT is an important statistic that describes the overall time spent by the drug in the body.
- Based on these findings, the researchers recommend an oral dosing regimen of 11 mg/kg of body weight every 24 hours for mature horses.
Cite This Article
APA
Ravis WR, Duran SH, Pedersoli WM, Schumacher J.
(1987).
A pharmacokinetic study of phenobarbital in mature horses after oral dosing.
J Vet Pharmacol Ther, 10(4), 283-289.
https://doi.org/10.1111/j.1365-2885.1987.tb00103.x Publication
Researcher Affiliations
- Department of Pharmacal Sciences, School of Pharmacy, Auburn University, AL.
MeSH Terms
- Absorption
- Administration, Oral
- Animals
- Half-Life
- Horses / metabolism
- Phenobarbital / administration & dosage
- Phenobarbital / pharmacokinetics
Citations
This article has been cited 3 times.- Yates LM, Aleman M, Knych HK, Knipe MF, Crowe CM, Chigerwe M. Pharmacokinetics of Intravenous and Oral Phenobarbital Sodium in Healthy Goats.. Front Vet Sci 2020;7:86.
- Cochrane SM, Black WD, Parent JM, Allen DG, Lumsden JH. Pharmacokinetics of phenobarbital in the cat following intravenous and oral administration.. Can J Vet Res 1990 Jan;54(1):132-8.
- Cochrane SM, Parent JM, Black WD, Allen DG, Lumsden JH. Pharmacokinetics of phenobarbital in the cat following multiple oral administration.. Can J Vet Res 1990 Jun;54(3):309-12.
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