Denmark health authority warns of potent synthetic opioid Cyclorphin

The Danish Health Authority (Sundhedsstyrelsen) has issued a warning after Cyclorphin, a highly potent synthetic opioid, was detected in Denmark during an autopsy and a drug seizure. The substance, many times stronger than morphine, was previously noted in Germany and added to the EU’s list of controlled narcotics on 3 July 2025.

Cyclorphin can cause acute poisoning at very small doses, with symptoms including euphoria, reduced consciousness, nausea, low blood pressure, slow pulse and respiratory depression that can lead to death. The authority advises that treatment should be administered promptly with naloxone, often requiring repeated or higher doses than usual. Unit chief Tanja Popp said, “We are concerned about these strong opioids because the risk of poisoning or overdose is great,” and the warning was sent to organisations and partners working with drug users.