Overview of SR-17018

What it is, in one minute

Quick reference

Compound name

SR-17018

Common short forms

SR-17, SR

CAS number

2134602-45-0

Chemical class

Substituted piperidine benzimidazolone (orphine-class designer opioid)

Receptor target

μ-opioid receptor (MOR), with much lower κ-OR affinity and negligible δ-OR affinity

Functional classification

Atypical biased / partial μ-opioid receptor agonist; non-competitive at MOR

Original publication

Schmid et al., Cell, 2017

Patent

Filed 2016 (Scripps Research / Bohn lab)

Approved medical use

None. Not approved by FDA, EMA, or any national regulator.

First reported in unregulated drug supply

2023

Reported community use cases

Self-administered taper aid for opioid dependence (kratom, nitazenes, fentanyl, methadone, ODSMT, buprenorphine, prescription opioids)

Reversibility

Effects reversible by opioid antagonists (naloxone, naltrexone) in animal models

Why it was made

The μ-opioid receptor turns on at least two cellular signaling cascades when activated. For years, the dominant theory in opioid pharmacology held that one of those cascades — β-arrestin2 recruitment — drove the most dangerous effects of opioids, including respiratory depression, while the other (G-protein signaling) drove pain relief. If that were true, a drug that turned on G-protein signaling without turning on β-arrestin recruitment could relieve pain with a wider safety margin.

SR-17018 was designed to test that hypothesis. In the 2017 paper that introduced it, the authors reported a therapeutic window for SR-17018 of 26–105 (respiratory depression relative to pain relief in mice) — far higher than morphine's 5–21 or fentanyl's 2–5[1].

What follow-up studies found

See Mechanism of action for the molecular detail and Preclinical pharmacology for the breathing data. The short version: SR-17018 has a wider therapeutic window than fentanyl or morphine in some mouse experiments, but it is not free of respiratory depression, and the safety advantage is dose- and route-dependent.

What we know about humans

What does exist is a body of self-reports from online communities (mostly from 2024 forward) describing the use of SR-17018 as a taper aid for people dependent on other opioids — including high-potency synthetic opioids like fentanyl and nitazenes[5]. These reports are useful as descriptive data, but they are unverified, unaudited, and subject to severe selection bias. We cover them in detail in Reported effects in humans.

Where to go from here

• If you came for the chemistry, head to Chemistry & identity.
• If you came to understand the biased-agonism story, Mechanism of action covers the original claim and the rebuttals.
• If you came because you or someone close to you uses this compound, the most important page is Safety considerations.
• If you came to find out whether it's legal, see Legal status for U.S. and international.
• If you want every paper we cite in one place, the Bibliography has direct links.