<unk>  () (brand names Lethidrone, Nalline), also known as N-allylnormorphine, is a mixed opioid agonist–antagonist with opioid antagonist and analgesic properties. It was introduced in 1954 and was used as an antidote to reverse opioid overdose and in a challenge test to determine opioid dependence.<unk>  was the second opioid antagonist to be introduced, preceded by nalodeine (N-allylnorcodeine) in 1915 and followed by naloxone in 1960 and naltrexone in 1963. Due to potent activation of the κ-opioid receptor,<unk>  produces side effects such as dysphoria, anxiety, confusion, and hallucinations, and for this reason, is no longer used medically.
Nalorphine
Morphine
Fentanyl
Codeine
Naloxone
Betamethadol
Alfentanil
Esketamine