The analgesic effect of nalbuphine and its long-acting prodrug, nalbuphine pivalate, in rats.
BACKGROUND
Nalbuphine is an opioid-analgesic with agonist-antagonist properties. Recently, we have synthesized a nalbuphine prodrug, nalbuphine pivalate. The aim of the present study was to evaluate the analgesic effect and the analgesic duration of this prodrug.


METHODS
Forty-eight male Sprague-Dawley rats (4 groups, n = 12 in each group) were used. Rats in group 1 received nalbuphine HCl 25 mumol/kg (in saline) intramuscular injection; rats in group 2 received nalbuphine pivalate 25 mumol/kg (in sesame oil) intramuscular injection, whereas those in groups 3 and 4 received saline and sesame oil respectively. The analgesic effects of testing agents were evaluated using the cold ethanol tail-flick test (-30 degrees C).


RESULTS
Both nalbuphine HCl and nalbuphine pivalate demonstrated significant analgesic effects. The analgesic duration of nalbuphine HCl was 2 h while that of nalbuphine pivalate was 30 h.


CONCLUSIONS
Nalbuphine pivalate has a very long duration of analgesic action. This fascinating finding is worth further evaluation.
Chen
Kuan-Ting
KT
Department of Anesthesiology, Chi-Mei Medical Center, Tainan, Taiwan, R.O.C.
Hu
Oliver Yoa-Pu
OY
Ho
Shung-Tai
ST
Chen
Yu-Wen
YW
Wang
Jhi-Joung
JJ
D000701:Analgesics, Opioid / Q000494:pharmacology*; D000818:Animals; D007273:Injections, Intramuscular; D008297:Male; D009266:Nalbuphine / Q000031:analogs & derivatives* / Q000494:pharmacology*; D011355:Prodrugs / Q000494:pharmacology*; D051381:Rats; D017207:Rats, Sprague-Dawley
D000701:Analgesics, Opioid; D011355:Prodrugs; C432108:nalbuphine pivalate; D009266:Nalbuphine