Phenoperidine

Phenoperidine, marketed as its hydrochloride as Operidine or Lealgin, is an opioid used as a general anesthetic. It is a derivative of isonipecotic acid, like pethidine, and is metabolized in part to norpethidine. It is 20-200 times as potent as pethidine as an analgesic.

In humans 1 milligram is equipotent with 10 mg morphine. It has less effect on the circulatory system and is less hypnotic than morphine, but it has about the same emetic effect. The nausea can be prevented by giving droperidol or haloperidol. After an intravenous dose the analgesia sets in after 3-5 minutes.

Phenoperidine shares structural similarities with both pethidine and haloperidol (and related butyrophenone antipsychotics, e.g. droperidol). While not commonly used today in clinical practice, it is of historical interest as a precursor in the development of some of the most widely used neuroleptic drugs on the market today.