A new synthetic opioid, cychlorphine, is gaining attention in forensic and public health news.

Cychlorphine, known scientifically as N-propionitrile chlorphine, is a synthetic opioid in an emergent subclass of novel synthetic opioids called orphine analogues (or orphines), and are structurally similar to other benzimidazolones (e.g., brorphine, chlorphine). The orphine analogues first emerged in recreational drug markets in 2020. This novel opioid subclass continues to diversify, with at least six analogues confirmed in recent years. The positivity of N-propionitrile chlorphine, specifically in fatal drug overdoses, has increased since mid-2025.

In vitro pharmacology data show this drug to be approximately 10x more potent than fentanyl. Like fentanyl, and other μ-opioid receptor agonists, responses are expected to be similar and produce CNS depression, respiratory depression and miosis.

Cychlorphine is being mixed with other illicit drugs, placing users at risk of accidental exposure. Co-detection with other substances including fentanyl, novel benzodiazepines, nitazene analogues and carfentanil has been documented in overdose cases.

Cychlorphine may not be detectable through standard fentanyl test strips. Naloxone can still be effective, but multiple doses may be required due to the drug’s extreme potency, potentially delaying life-saving treatment.