Objective—To determine pharmacokinetics and
selected cardiopulmonary effects of fentanyl in isoflurane-anesthetized rhesus monkeys.
Animals—6 adult male rhesus monkeys.
Procedure—Fentanyl (8 mg/kg of body weight, IV)
was administered to 6 monkeys anesthetized with
isoflurane. End-tidal isoflurane concentration and
esophageal temperature were kept constant, and
ventilation was mechanically assisted. Heart rate,
rhythm, aortic blood pressure, and blood pH, gas, and
fentanyl concentrations were determined before and
for 8 hours after administration of fentanyl.
Pharmacokinetics of fentanyl were derived by use of
noncompartmental methods based on statistical
Results—Heart rate and mean arterial pressure
decreased transiently following fentanyl administration.
Maximal decreases were observed 5 to 15 minutes
after administration. Arterial pH, PaCO2, and PaO2
ranged from 7.46 ± 0.04 to 7.51 ± 0.05 units, 29.2 ± 3
to 34.6 ± 4.4 mm Hg, and 412.6 ± 105.3 to 482.9 ±
71.2 mm Hg, respectively. The clearance, volume of
distribution area, volume of distribution steady state,
mean residence time, area under the curve, elimination
rate constant, and half-life were 32.5 ± 2.48
ml/kg/min, 9.04 ± 1.91 L/kg, 7.0 ± 1.2 L/kg, 218.5 ±
35.5 min, 0.247 ± 0.019 mg/ml/min, 0.004 ±
0.001/min, and 192.0 ± 33.5 min, respectively.
Conclusions and Clinical Relevance—Transient but
potentially clinically important decreases in heart rate
and mean arterial pressure were observed following
fentanyl administration. Distribution and clearance
data were similar to those reported for dogs and
humans. (Am J Vet Res 2000;61:931–934)