neuroleptics or tranquilizers) were investigated by the anesthesiologists De Castro and Mundeleer who coined the term neuroleptanalgesia, an anesthetic process that involves combining a major antipsychotic/neuroleptic or tranquilizer with a potent opioid analgesic to produce a detached, pain-free state.
This technique was widely used from the 1960s onwards, initially using a combination of phenoperidine and haloperidol, which was subsequently replaced in the early 1980s by a combination of fentanyl and droperidol.
Efforts were also made to develop compounds which combined both types of activity in a single molecule.
The technique has become less popular with the advent of more modern procedural sedation drug combinations, though it is still rarely used today as a combination of 2.5 mg droperidol and 50 μg (micrograms) of fentanyl in a ratio of 50:1.
This combination is characterized by immobility, analgesia, and variable amnesia.