Cychlorphine (N-Propionitrile chlorphine) is here

Have you heard of cychlorphine? From what I can find it’s on the street as a designer drug and thought to be an opioid with potency as high or higher than fentanyl.

I’ve seen an article about three deaths in north London related to this compound.

And I’ve also seen an article about this compound appearing in Toronto.

I’ve looked for cychlorphine on the DEA website, but they don’t have it listed yet. Neither does the National Drug Early Warning System.

Fortunately, a very recently published open access article is available that describes this compound. The authors note that cychlorphine is:

• a novel mu-opioid receptor agonist
• classified as a piperidine benzimidazolone derivative
• structurally similar to benzimidazolones and structurally distinct from nitazene opioids

They state that cychlorphine causes “pronounced” respiratory depression and that naloxone has not been shown to be effective in completely blocking its effects. And that the benzimidazolones were first described in a patent in the late 1960’s.

They add:

The detection of cychlorphine in a street formulation associated with opioid toxicity highlights the expanding diversity of non-fentanyl–related novel synthetic opioids encountered in emergency care. Clinicians and toxicologists should be alert to the potential appearance of piperidine benzimidazolone opioids in the illicit drug supply.

_{Sprague, J. E., Toms, J. A., & Ratermann, C. F. (2025). Non-fatal opioid overdose associated predominantly with the benzimidazolone, cychlorphine. Clinical Toxicology, 1–2. https://doi.org/10.1080/15563650.2025.2594070}