Norpipanone (INN, BAN; Hexalgon) is an opioid analgesic related to methadone which was developed in Germany and distributed in Hungary, Argentina, and other countries. It had originally not been under international control but upon observation of case reports of addiction it was reviewed and shortly thereafter became a controlled substance. In the United States, it is a Schedule I controlled substance (ACSCN 9636, zero annual manufacturing quota as of 2014). The salts in use are the hydrobromide (free base conversion ratio 0.806) and hydrochloride (0.902).