Wiktionary
properidine
n. (context pharmaceutical drug English) A particular narcotic painkiller.
Wikipedia
Properidine
Properidine is an opioid analgesic and the isopropyl analog of pethidine. Properidine is under international control and is listed in the United States under the Controlled Substances Act 1970 as a Schedule I Narcotic with an ACSCN of 9644 and a 2 gramme annual aggregate manufacturing quota as of 2014. The salt in use is the hydrochloride, with a free base conversion ratio of 0.88.