The irreversible narcotic antagonistic and reversible agonistic properties of the fumaramate methyl ester derivative of naltrexone

Eur J Pharmacol. 1981 Apr 9;70(4):445-51. doi: 10.1016/0014-2999(81)90355-1.


The fumaramate methyl ester derivatives of naltrexone (beta-FNA) and oxymorphone (beta-FOA) were both found to be reversible agonists on the guinea pig ileal longitudinal muscle preparation. In addition, beta-FNA possessed on irreversible antagonistic effect against morphine whereas beta-FOA had no such capacity. Analysis by pA2 values revealed that beta-FOA resembled pure agonists like morphine and enkephalin while beta-FNA resembled the mixed agonist-antagonists like nalorphine and pentazocine. The antagonism by beta-FNA was very selective in that it antagonized pure agonists but had little or no effect on the effects of either mixed agonist-antagonists, ethylketocyclazocine or other non-opiate-type agonists like norepinephrine.

Publication types

  • Research Support, U.S. Gov't, P.H.S.

MeSH terms

  • Affinity Labels
  • Animals
  • Ileum
  • Male
  • Mice
  • Muscle Contraction / drug effects
  • Muscle, Smooth / drug effects
  • Naloxone / analogs & derivatives*
  • Naltrexone / analogs & derivatives*
  • Naltrexone / pharmacology
  • Oxymorphone / analogs & derivatives
  • Oxymorphone / pharmacology
  • Receptors, Opioid / drug effects*
  • Receptors, Opioid / metabolism
  • Structure-Activity Relationship


  • Affinity Labels
  • Receptors, Opioid
  • Naloxone
  • Naltrexone
  • beta-funaltrexamine
  • oxymorphone fumarate methyl ester
  • Oxymorphone