Overview
- NIH scientists reported in Nature that DFNZ delivered strong pain relief in rats without depressing breathing.
- The team found DFNZ after PET scans of a related compound (FNZ) showed brief brain entry, which led them to the active metabolite driving the lasting effect.
- DFNZ acted at the mu‑opioid receptor as a high‑efficacy superagonist yet produced little tolerance and only mild withdrawal signs in repeated dosing.
- Rats self‑administered DFNZ but stopped when it was switched to saline, matching brain data that show slow dopamine release rather than fast spikes tied to strong drug cues.
- The authors say DFNZ could be explored for pain care and possibly opioid use disorder, though it remains untested in people and comes from a class once shelved in the 1950s for overdose risk.