W-18 is a compound in a series of 32 substances (named W-1 to W-32) that were first synthesized in academic research on analgesic drug discovery in the 1980s and appeared as a designer drug in the 2010s.
W-18 was invented at the University of Alberta by a lab working on analgesic drug discovery in the 1980s, and preliminary studies in animals showed it had pain-killing activity in mice.
The chemical was detected in connection with recreational drug use as substitute for other controlled substances in Europe in 2013, and in the United States. In Canada, Alberta Law Enforcement Response Teams (ALERT) seized four kilograms of W-18 in a drug bust in Edmonton in December 2015 and W-18 was also detected by Health Canada in at least three of 110 fentanyl tablets seized from a Calgary home in August 2015.
W-18 was commonly reported to be an opioid in the popular press in the 2010s, which was later revealed not to be correct. W-18 was found to obtain weak activity at both sigma receptors and the translocator protein (peripheral benzodiazepine receptor). It also inhibits hERG binding, an important antitarget in drug discovery, which possibly causes cardiovascular side-effects.