What is "nalmexone"

n. A semisynthetic mixed opioid agonist-antagonist with analgesic and narcotic antagonist properties.

Nalmexone ( INN) (code names EN-1620A, UM-592), or nalmexone hydrochloride ( USAN), is a semisynthetic, opioid partial agonist or mixed agonist- antagonist with both analgesic and narcotic antagonist properties that was never marketed. In clinical studies it was found to have comparable analgesic efficacy to morphine, though with several-fold reduced potency. In addition, nalmexone's side effects, the most common of which were sleepiness and sweating, were reported to be similar to those of morphine, albeit with a noticeably higher degree of incidence.