Antinociceptive and respiratory effects of nalbuphine in rhesus monkeys.
Antinociceptive and respiratory effects of nalbuphine and other opioids were studied in rhesus monkeys. In a thermal, tail withdrawal assay, the kappa agonist enadoline and the mu agonists alfentanil and fentanyl produced maximum antinociceptive effects in all subjects and over a wide range of temperatures, whereas nalbuphine produced antinociceptive effects in only some subjects and only when the water temperature was < or = 50 degrees C. Naltrexone antagonized the antinociceptive effects of nalbuphine, alfentanil and enadoline; however, the magnitude of antagonism was not equal among agonists. In subjects that did not show an antinociceptive response to nalbuphine, nalbuphine (3.2-10.0 mg/kg) antagonized the antinociceptive effects of fentanyl but not enadoline. The irreversible opioid antagonist clocinnamox produced a parallel shift to the right in the nalbuphine dose-effect curve 1 hr after administration and decreased the maximum effect produced by nalbuphine 24 and 48 hr after administration. Nalbuphine had modest respiratory-depressant effects in monkeys breathing air and attenuated hyperventilation produced by 5% CO2. In contrast, alfentanil had marked respiratory-depressant effects in monkeys breathing air or 5% CO2 in air and these effects were antagonized by nalbuphine. Taken together, these results suggest nalbuphine has low efficacy at mu opioid receptors; however, quantitative differences between alfentanil and nalbuphine indicate a second (non-enadoline sensitive) receptor might also be important for the antinociceptive effects of nalbuphine.
Department of Pharmacology, Louisiana State University Medical Center, New Orleans.
L R
LR
Gerak
E R
ER
Butelman
J H
JH
Woods
C P
CP
France
D015760:Alfentanil / Q000494:pharmacology; D000698:Analgesia; D000818:Animals; D004305:Dose-Response Relationship, Drug; D005260:Female; D005283:Fentanyl / Q000494:pharmacology; D008253:Macaca mulatta; D008297:Male; D009266:Nalbuphine / Q000494:pharmacology*; D017473:Receptors, Opioid, kappa / Q000187:drug effects; D017450:Receptors, Opioid, mu / Q000187:drug effects; D012119:Respiration / Q000187:drug effects*
D017473:Receptors, Opioid, kappa; D017450:Receptors, Opioid, mu; D015760:Alfentanil; D009266:Nalbuphine; D005283:Fentanyl