Phenoperidine[2][3] (Operidine or Lealgin), is an opioid analgesic which is structurally related to pethidine and is used clinically as a general anesthetic.

The greatly increased potency essentially eliminates the toxic effects of norpethidine accumulation which are seen when pethidine is administered in high doses or for long periods of time.

[5] His two prototype drugs were methadone and pethidine, each which had been invented in 1930s by Otto Eisleb, who worked for IG Farben.

[5] In 1958, the same line of work yielded "one of the greatest advances of the 20th century psychiatry", haloperidol,[5] as well as diphenoxylate, which lacked the opioid's analgesic properties but still stopped peristalsis in the intestines, a typical side effect of opioids; Janssen brought diphenoxylate to market as a drug to treat diarrhea.

[9][10] In the US it is classified as a Drug Enforcement Administration (DEA) Schedule I controlled substance opiate with a corresponding code 9641.