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PHARMACOLOGY 
OXYPHENBUTAZONE 3.5 mg/kg 
40-1 
1 2 J 15 6 7 
Ti l ! -y.ri 
b'lGVRE 13. — Disappearance of oxyphenbutazone from 
the plasma of several species following intravenous 
injection (3.5 mg/kg). 
pies, pigs and foals born of dams which were 
receiving the drug. 
Figure 17 shows the disappearance of drug 
from the plasma of goats and dogs following an 
anesthetic dose of pentobarbital. The drug was 
given to effect, blood samples were collected pe- 
riodically, and the subjects reflexes were evalu- 
ated periodically. These data indicated that the 
species diiference in duration of action of drug 
is related to kinetic considerations rather than 
to differences in receptor sensitivity. Reflexes 
reappeared at almost identical drug concentra- 
tions in blood. The difference in duration of ac- 
tion was due to the influence of distribution vol- 
umes on the overall kinetics. Disappearance of 
drug from the plasma of cats were very similar 
to that observed in the case of dogs. 
Disappearance of pentobarbital from the 
plasma of various species following I.V. admin- 
istration of drug (10 mg/kg) is shown in Fig- 
ure 18. The specific volumes of distribution are 
nearly identical for ponies, swine and dogs. 
That for the goat is larger, although it isn't ap- 
parent from the figure because the sampling pe- 
riod wasn't long enough to adequately define the 
elimination phase. 
Plasma protein binding didn't have a signifi- 
cant influence on the overall kinetics as species 
differences were not observed. Extent of bind- 
ing was about 70% in all species. 
Chronic administration of pentobarbital to 
the various species did not produce a consistent 
effect on kinetic parameters during the first 
three months. At the fourth, fifth and sixth 
months, the half-life of the drug was increased 
by about 100%. Induction of enzymes, as mani- 
fested by a shorter half -life was not observed in 
any subject. 
Tetra ethyla m m on i u m 
The kinetics of disappearance of TEA was in- 
vestigated in dogs, cats and goats following in- 
travenous administration of TEA (50 mg and 2 
OXYPHENBUTAZONE 10 mg/kg 
Figure 14. — Disappearance of oxyphenbutazone from 
the plasma of several species following intravenous 
injection (10 mg/kg). 
