Hydromorphinol, an opioid, and is a derivative of morphine and possesses similar properties: sedation, analgesia, and respiratory depression. Hydromorphinol is under the control according to US Single Convention 1961.

Hydromorphinol:
https://drugs.ncats.io/drug/1O00P9X5C1

Hydromorphinol is distributed under the trade name Numorphan Oral in some countries and there are generics; it is used mainly in northern Europe for the same spectrum of indications as oxymorphone, including induction of anaesthesia. In my experience when getting four root canal treatments at the same time back in the day, the rush (physical effect including vasodilation and histamine release) and bang (rapid onset of euphoria) is somewhat more intense than hydromorphone or oxymorphone, but no pins & needles like morphine, and it does last longer and feels a lot like oxymorphone from T + 10 minutes on as well. The drop in body temperature, especially when I am overdue for a dose, is one of my favorite opioid effects, and it was quite apparent with hydromorphinol. Orally, sublingually, and intranasally, it is like oxymorphone to a great extent. Four root canals at the same time plus an extraction sounds really rough, but in no time I felt like dancing right there in the chair.

Bluelight Forum Hydromorphinol:
https://www.bluelight.org/xf/threads/hydromorphinol.616467/

Hydromorphinol is an opiate analogue that is a derivative of morphine. It has similar effects to morphine such as sedation, analgesia and respiratory depression, but is twice as potent as morphine. Hydromorphinol was developed in Austria in 1932. In the United States, it was never available. Hydromorphinol is metabolized mainly in the liver in the same fashion as many other opioids.