Aniledrine is a narcotic pain reliver. The drug was prescribed as an analgesic in anaesthesia (Leritine brand name), however, it is no longer available on the market. Although the exact mechanism is not fully understood, aniledrine appears to elicit its action by binding to endorphine receptors in CNS.

Metopon was developed as an analgesic opium derivative. This drug has a high affinity to the mu-opioid receptor and produces antinociception through this receptor. Metopon was available in Canada only in tablet form for oral administration; however, because of the drug addiction, the Drug Addiction Committee recommended its limited use.

Bezitramide was developed as an orally long-acting analgesic compound and was marketed under the brand name Burgodin. The overdose of this drug caused death that is why it was withdrawn from the market.

Eptazocine is an opioid analgesic which was introduced in 1987 by Morishita in Japan . It acts as a mixed κappa opioid receptor agonist and mu-opioid receptor antagonist.