Isotonitazene – more commonly known as iso – is an opioid drug with side effects similar to those of fentanyl. The drug is over 100 times more powerful than morphine. Iso is a synthetic version of etonitazene, an incredibly potent opioid that was developed in the 1950s. While etonitazene is controlled both nationally and internationally, iso isn’t yet listed on the U.S. Drug Enforcement Administration’s controlled substances list – so it remains a legal substance.
The iso drug is usually sold as an off-white powder that is cut into other drugs or sold as a legal replacement to opioids. While it’s a new synthetic opioid on the market, iso is now considered a prevalent substance across the U.S. and has been linked to many cases of fatal overdoses.