title: The analgesic effect of nalbuphine and its long-acting prodrug, nalbuphine pivalate, in rats.
abstract: 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.
authors.affiliation: Department of Anesthesiology, Chi-Mei Medical Center, Tainan, Taiwan, R.O.C.
authors.forename: Kuan-Ting
authors.initials: KT
authors.lastname: Chen
authors.forename: Oliver Yoa-Pu
authors.initials: OY
authors.lastname: Hu
authors.forename: Shung-Tai
authors.initials: ST
authors.lastname: Ho
authors.forename: Yu-Wen
authors.initials: YW
authors.lastname: Chen
authors.forename: Jhi-Joung
authors.initials: JJ
authors.lastname: Wang
mesh_terms: 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
chemical_list: D000701:Analgesics, Opioid; D011355:Prodrugs; C432108:nalbuphine pivalate; D009266:Nalbuphine