The intramuscular bioavailability of a phenylbutazone preparation in the horse.
Abstract: The plasma concentrations of phenylbutazone (PBZ) and its major metabolites, oxyphenbutazone (OPBZ) and gamma-OH-phenylbutazone (OHPBZ) were determined for up to 72 h in six horses, following intravenous (i.v.) and intramuscular (i.m.) administration of 4 g phenylbutazone, 20 ml Phenylarthrite Ventoquinol (Vetoquinol Spécialités Pharmaceutiques Vétérinaires, Magny-Vernois, 70200 Lure, France). After i.v. dosing the plasma disposition was best described by a two-compartment open model. The hydroxylated metabolites OPBZ and OHPBZ were present in detectable concentrations for 72 h and 48 h, respectively. After 36 h the OPBZ concentrations exceeded plasma PBZ concentrations. The plasma disposition following i.m. injection could be described by a one-compartment open model. The hydroxylated metabolites OPBZ and OHPBZ were present in detectable concentrations for 72 h and 36 h, respectively. Only after 72 h was the concentration of OPBZ in plasma higher than the concentration of PBZ. The mean i.m. bioavailability of phenylbutazone was calculated to be 91.7 +/- 10.1%.
Publication Date: 1993-12-01 PubMed ID: 8126767DOI: 10.1111/j.1365-2885.1993.tb00216.xGoogle Scholar: Lookup
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- Journal Article
Summary
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This research investigates the plasma concentrations of phenylbutazone (PBZ) and its metabolites in horses after it is administered intravenously and intramuscularly. The researchers found that the plasma disposition of PBZ and metabolites differs somewhat depending on the method of administration, with a 91.7% bioavailability via intramuscular injection.
Study Design and Methods
- The study was performed on six horses to whom 4g of phenylbutazone were administered either intravenously or intramuscularly.
- The concentrations of phenylbutazone and its major metabolites (oxyphenbutazone and gamma-OH-phenylbutazone) in the horses’ plasma were monitored and recorded over a period of 72 hours.
Findings from Intravenous Administration
- When phenylbutazone was administered intravenously, the researchers found that the distribution of the drug in the plasma could be best described by a two-compartment open model. This is a pharmacokinetic model where the body is considered as two compartments, one for the blood and the other for the tissue, and the drug is interchanged between these compartments.
- The metabolite oxyphenbutazone was detectable in the plasma for the entire 72 hours, and gamma-OH-phenylbutazone was detectable for 48 hours.
- 36 hours after the intravenous dosing, the concentration of oxyphenbutazone in the plasma exceeded the concentration of phenylbutazone.
Findings from Intramuscular Administration
- The intramuscular injection of phenylbutazone followed a one-compartment open model, where the body is considered as a single entity for the process of drug distribution.
- The metabolite oxyphenbutazone remained detectable for 72 hours, while gamma-OH-phenylbutazone was present for 36 hours after the injection.
- The concentration of oxyphenbutazone in the plasma was only higher than the concentration of phenylbutazone 72 hours after the intramuscular injection.
Conclusion
- The mean intramuscular bioavailability of phenylbutazone — that is, the degree and rate at which the active ingredient is absorbed into the systemic circulation and is made available at the site of action — was calculated to be approximately 91.7%
Cite This Article
APA
Landuyt J, Delbeke FT, Debackere M.
(1993).
The intramuscular bioavailability of a phenylbutazone preparation in the horse.
J Vet Pharmacol Ther, 16(4), 494-500.
https://doi.org/10.1111/j.1365-2885.1993.tb00216.x Publication
Researcher Affiliations
- Laboratory of Veterinary Pharmacology and Toxicology, Faculty of Veterinary Medicine, University of Ghent, Belgium.
MeSH Terms
- Animals
- Biological Availability
- Horses / metabolism
- Injections, Intramuscular / veterinary
- Injections, Intravenous / veterinary
- Male
- Muscles / metabolism
- Oxyphenbutazone / blood
- Phenylbutazone / analogs & derivatives
- Phenylbutazone / blood
- Phenylbutazone / pharmacokinetics
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