Utopioid (drug class)

Utopioids (U-type opioids) are a class of synthetic opioid analgesic drugs first developed in the 1970s by the pharmaceutical company Upjohn. However, they were never marketed for medical use. Some compounds from this class have been used for scientific research as model kappa opioid receptor agonists. In the mid-2010s, one mu opioid receptor selective compound from this class, U-47700, re-emerged as a designer drug and became widely sold around the world for several years before being banned in various jurisdictions from 2016 onwards. Following the prohibition of U-47700, a number of related compounds have continued to appear on illicit drug markets. They are often marketed online or included as components in mixtures sold under the guise of "street heroin." U-47700 itself is the most potent mu opioid agonist from this class, around 7-10x the potency of morphine. Some other compounds such as 3,4-MDO-U-47700 and N-Ethyl-U-47700 retain similar mu selectivity but with lower potency similar to that of morphine, or have a mixture of mu and kappa mediated effects, such as U-48800. Most utopioid derivatives are however selective kappa agonists, which may have limited abuse potential as dissociative hallucinogens, but do not alleviate withdrawal distress in opioid dependent individuals or maintain addiction in a typical sense. Nevertheless, this has not stopped them from being sold as designer drugs, and a number of these compounds are now banned in many jurisdictions alongside U-47700 itself.