Pc. Mills et al., PHENYLBUTAZONE IN RACING GREYHOUNDS - PLASMA AND URINARY RESIDUES 24 AND 48 HOURS AFTER A SINGLE INTRAVENOUS ADMINISTRATION, Australian Veterinary Journal, 72(8), 1995, pp. 304-308
The concentrations of phenylbutazone (PBZ), oxyphenbutazone (OPBZ) and
gammahydroxyphenylbutazone (OHPBZ) in plasma and urine from 50 Greyho
unds 24 and 48 h after the intravenous administration of a single dose
of PBZ (30 mg/kg) were measured. The 24 h plasma concentrations of OP
BZ and OHPBZ, the 48 h plasma concentration of OHPBZ and the 24 h urin
ary concentration of PBZ were normally distributed, while log transfor
mations were required before the 24 h plasma concentration of PBZ and
the 24 and 48 h urinary concentrations of OPBZ and OHPBZ became normal
ly distributed, The 95%, 99%, 99.9% and 99.99% upper predicted confide
nce intervals for both 24 h and 48 h plasma and urinary concentrations
demonstrated wide potential variation in the concentration of the ana
lytes should PBZ be administered to Greyhounds. The 24 h plasma and ur
inary concentrations of PBZ were weakly correlated, but no similar rel
ationship existed for OPBZ or OHPBZ. The urinary concentrations of eac
h analyte were not affected by the trainer or sex of the Greyhound or
the urinary pH, We conclude that it would be impossible to predict the
timing of the PBZ administration or the plasma concentration of PBZ f
rom the measurement of the concentration of PBZ in a single sample of
urine.