Spinal antinociception by dexmedetomidine, a highly selective alpha 2-adrenergic agonist

Pharmacol Toxicol. 1991 Feb;68(2):140-3. doi: 10.1111/j.1600-0773.1991.tb02052.x.


The antinociceptive effects of dexmedetomidine, a highly selective new alpha 2-adrenoceptor agonist, were evaluated in rats after intrathecal, intraperitoneal and subcutaneous administration. Antinociception was tested using the tail-flick method. Both 3 and 6 micrograms of intrathecal dexmedetomidine produced maximal antinociception within 10 min. The effect lasted for up to 6 hr. The smaller dose of 1.5 micrograms produced a mean antinociception of 50% (of the maximum possible effect, MPE%) which lasted for about 2 hr. Subcutaneous atipamezole, a specific alpha 2-adrenergic antagonist completely abolished the antinociception produced by intrathecal dexmedetomidine. When given intraperitoneally, dexmedetomidine produced on average a 50% antinociceptive effect with the highest dose of 60 micrograms/kg. The lower doses of 10 and 30 micrograms/kg were ineffective. After subcutaneous administration a maximal effect was achieved with 120 micrograms/kg, a 70% effect, on average, with 60 micrograms/kg and a short lasting effect of 60% with 30 micrograms/kg. In conclusion, dexmedetomidine is a very potent antinociceptive agent when given intrathecally to rats.

Publication types

  • Comparative Study

MeSH terms

  • Adrenergic alpha-Agonists / administration & dosage
  • Adrenergic alpha-Agonists / pharmacology*
  • Analgesics*
  • Animals
  • Dose-Response Relationship, Drug
  • Imidazoles / administration & dosage
  • Imidazoles / antagonists & inhibitors
  • Imidazoles / pharmacology*
  • Injections, Intraperitoneal
  • Injections, Spinal
  • Injections, Subcutaneous
  • Male
  • Medetomidine
  • Pain Measurement
  • Rats
  • Rats, Inbred Strains
  • Reaction Time / drug effects


  • Adrenergic alpha-Agonists
  • Analgesics
  • Imidazoles
  • atipamezole
  • Medetomidine