The intramuscular bioavailability of a phenylbutazone preparation in the horse.
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%.
Landuyt
J
J
Laboratory of Veterinary Pharmacology and Toxicology, Faculty of Veterinary Medicine, University of Ghent, Belgium.
Delbeke
F T
FT
Debackere
M
M
D000818:Animals; D001682:Biological Availability; D006736:Horses / Q000378:metabolism*; D007273:Injections, Intramuscular / Q000662:veterinary; D007275:Injections, Intravenous / Q000662:veterinary; D008297:Male; D009132:Muscles / Q000378:metabolism*; D010113:Oxyphenbutazone / Q000097:blood; D010653:Phenylbutazone / Q000031:analogs & derivatives / Q000097:blood / Q000493:pharmacokinetics*
C008072:gamma-hydroxyphenylbutazone; D010653:Phenylbutazone; D010113:Oxyphenbutazone