title: Nefopam potentiates morphine antinociception in allodynia and hyperalgesia in the rat.
abstract: The objective of this study was to resolve discrepancies regarding the possible antinociceptive synergy between morphine and nefopam in animal models of pain. Firstly, we have examined the antinociceptive activity of nefopam, a nonopioid antinociceptive compound that inhibits monoamine reuptake, in pain models of allodynia and hyperalgesia induced by carrageenan injection, or skin and muscle incision of the rat hind paw. Single subcutaneous administration of nefopam at 30 mg/kg blocked carrageenan- and incision-induced thermal hyperalgesia, and weakly but significantly diminished carrageenan-induced tactile allodynia. A weaker dose of nefopam (10 mg/kg) only reduced carrageenan-induced tactile allodynia and incision-induced thermal hyperalgesia. Secondly, we assessed the usefulness of the coadministration of nefopam with morphine. Combination of a nonanalgesic dose of nefopam (10 mg/kg) with a nonanalgesic dose of morphine (0.3 or 1.0 mg/kg) completely inhibited carrageenan- or incision-induced thermal hyperalgesia, respectively. In carrageenan-induced tactile allodynia, coadministration of weak analgesic doses of nefopam (10 and 30 mg/kg) with a nonanalgesic dose (1 mg/kg) or moderately analgesic dose (3 mg/kg) of morphine significantly reduced or reversed allodynia, respectively. In conclusion, coadministration of nefopam with morphine enhances the analgesic potency of morphine, indicating a morphine sparing effect of nefopam.
authors.affiliation: Laboratoires Biocodex, Service de Pharmacologie, Zac de Mercières, 60200 Compiègne, France. p.girard@biocodex.fr
authors.forename: Philippe
authors.initials: P
authors.lastname: Girard
authors.forename: Yannick
authors.initials: Y
authors.lastname: Pansart
authors.forename: Jean-Marie
authors.initials: JM
authors.lastname: Gillardin
mesh_terms: D000700:Analgesics / Q000627:therapeutic use*; D000818:Animals; D004357:Drug Synergism; D006930:Hyperalgesia / Q000188:drug therapy* / Q000503:physiopathology; D008297:Male; D009020:Morphine / Q000494:pharmacology / Q000627:therapeutic use*; D009340:Nefopam / Q000494:pharmacology / Q000627:therapeutic use*; D017288:Pain Threshold / Q000187:drug effects* / Q000502:physiology; D051381:Rats; D017207:Rats, Sprague-Dawley
chemical_list: D000700:Analgesics; D009340:Nefopam; D009020:Morphine