A newly emerging synthetic opioid being detected in fatal overdose investigations may not fully respond to naloxone, prompting forensic officials to advise law enforcement to follow standard fentanyl safety protocols while toxicology data continues to develop.
The drug, N-Propionitrile Chlorphine, also known as cychlorphine, has been identified in 19 overdose death investigations in East Tennessee, with 12 confirmed and seven pending laboratory confirmation, according to the Knox County Regional Forensic Center. Forensic officials say laboratory data indicate the compound may be approximately 10 times more potent than fentanyl.
What investigators are seeing in Tennessee
Chris Thomas, chief administrative officer and director of the forensic center, said officers should treat suspected exposures the same way they would fentanyl.
“There is currently insufficient data to determine whether this compound presents additional dermal exposure risk,” Thomas said. “Follow fentanyl protocols.”
In most confirmed cases, cychlorphine was detected alongside fentanyl and methamphetamine. In one confirmed case, however, it was the only drug identified. That case involved a measured concentration of approximately 0.5 nanograms in femoral blood, which Thomas described as extremely low.
Unlike fentanyl, cychlorphine does not appear on routine toxicology panels. Detection requires expanded laboratory analysis and, in some cases, referral to research laboratories for confirmation. The forensic center submits femoral blood samples to NMS Labs for toxicology testing. If the compound is detected, samples are forwarded to a research laboratory for confirmation.
Officials caution that the number of confirmed cases may reflect testing capability rather than geographic prevalence. Jurisdictions without expanded analytical panels may not detect the compound even if present.
Naloxone still advised
Thomas said naloxone, commonly known as Narcan, may not be fully effective in reversing overdoses involving cychlorphine but should still be administered. Responders cannot immediately determine which opioid is present at a scene, he said.
“Always try,” Thomas said, referring to naloxone administration.
Cychlorphine belongs to a subclass of synthetic opioids known as orphine analogues. National forensic researchers first identified the compound in 2024, and a January 2026 public alert from the Center for Forensic Science Research and Education reported an increase in fatal overdoses in which the drug was detected.
At this stage, forensic officials are not recommending new field procedures beyond established fentanyl safety measures. Existing opioid response protocols remain appropriate while additional data continues to emerge.
