In recreational drug circles in the United States, Novel Psychoactive Substances (NPS) - particularly new synthetic opioids - are regularly released. In the interest of public health and safety, it is crucial for forensic scientists to understand these compounds and develop effective post-mortem detection tests. 

The most recent addition to the list of NPS is Metonitazene, which first emerged in 2020, and then began to proliferate in 2021 in response to the scheduling of brorphine, another very recent NPS. To expand our knowledge on this compound, scientists at The Center for Forensic Science Research and Education (CFSRE), with support from NMS Labs, explored its concentration, co-occurrence with other drugs, toxicity, and metabolism. 

Liquid chromatography—mass spectrometry confirmed the presence of this compound in biological samples taken from 20 post-mortem forensic investigation cases. Its average concentrations in blood and urine were 6.3 and 15 ng/mL respectively. 

In 55% of cases, it was found in combination with fentanyl and in 45% cases in combination with other NPS, including a variety of Benzodiazepines such as Flualprazolam and Clonazolam, synthetic opioids such as butonitazene, and hallucinogens such as N-ethyl deschloroketamine. In 30% cases it was the sole identified opioid. In the 15% of cases where Metonitazene was the sole drug of interest, it was listed as the cause of death, and the death was ruled accidental. 

The metabolism of Metonitazene is similar to that of Isotonitazene, a close analogue NPS that emerged prior to Metonitazene.  

These findings demonstrate the potential for small amounts of this compound to be lethal, thus highlighting the importance of including it in postmortem toxicology panels and forensic testing protocols.