Is a 4-Phenylpiperidine derivative that is related to Pehidine. It is roughly 4x as potent as the parent compound, does not cause convulsions such as Pethidine.

Morpheridine is a pethidine analog with strong analgesic activity. Morpheridine 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 United Nations drug conventions.

Morpheridine:
https://drugs.ncats.io/drug/1854GKB41Y

Opioid pain reliever not currently used in medicine