Wiktionary
morpheridine
n. A strong analgesic, a 4-phenylpiperidine derivative related to pethidine.
Wikipedia
Morpheridine
Morpheridine (Morpholinoethylnorpethidine) is a 4- phenyl piperidine derivative that is related to the opioid analgesic drug pethidine (meperidine). It is a strong analgesic with around 4 times the potency of pethidine, and unlike pethidine, does not cause convulsions, although it produces the standard opioid side effects such as sedation and respiratory depression.
Morpheridine is not currently used in medicine and is a Schedule I drug which is controlled under UN drug conventions.