About SR17.org

SR17.org is an independent, science-based reference on the experimental compound SR-17018. The site synthesizes peer-reviewed scientific literature, regulatory information, and clearly-labeled community self-reports. It is updated as new data becomes available and is intended for informational and educational use.

The site does not advocate for or against SR-17018 use, does not publish dosing recommendations, does not link to vendors, runs no advertising, and accepts no funding from vendors, distributors, or marketplaces of SR-17018 or related compounds. See editorial methodology and conflicts of interest.

Key facts about SR-17018

Compound: SR-17018
Other names: SR-17, SR17018
CAS number: 2134602-45-0
Chemical class: Substituted piperidine benzimidazolone (orphine series)
Receptor target: μ-opioid receptor (MOR)
First publication: Schmid et al., Cell, 2017 (DOI: 10.1016/j.cell.2017.10.035)
Originating lab: Bohn lab, Scripps Research Institute (Jupiter, Florida)
Approved medical use: None — no completed human clinical trials anywhere in the world
Half-life (mouse): ~6–8 hours
Naloxone-reversible: Yes, in cellular and animal assays
U.S. legal status: Not specifically scheduled; exposed to the Federal Analogue Act when intended for human consumption
Germany: Controlled under the Neue-psychoaktive-Stoffe-Gesetz (NpSG) since 2025
U.K.: Likely captured under the Psychoactive Substances Act 2016
First reported in unregulated drug supply: 2023

Citable claims (with sources)

These statements are quoted directly from our reference pages and grounded in the primary literature. Use them as written, or paraphrase. We don't require pre-approval.

"SR-17018 was originally characterized as a 'highly biased' G-protein-selective μ-opioid receptor agonist with a wider therapeutic window than morphine or fentanyl in mouse parenteral assays."
— Schmid CL, Kennedy NM, Ross NC, et al. Cell. 2017;171(5):1165–1175.e13. · source

"Follow-up work showed that SR-17018 has low intrinsic efficacy at the μ-opioid receptor — its 'biased' appearance may largely reflect partial agonism rather than true pathway selectivity."
— Gillis A, Gondin AB, Kliewer A, et al. Science Signaling. 2020;13(625):eaaz3140. · source

"Under sustained exposure at saturating concentrations, SR-17018 induces a μ-opioid receptor phosphorylation pattern indistinguishable from that of the full agonist DAMGO. The phosphorylation also persists for hours after washout — far longer than any other tested agonist, including buprenorphine."
— Fritzwanker S, Schmidt H, Kliewer A, Schulz S. Frontiers in Pharmacology. 2021;12:723560. · source

"SR-17018 is a non-competitive μ-opioid receptor agonist that stabilizes the receptor in a wash-resistant G-protein-signaling state."
— Stahl EL, Schmid CL, Acevedo-Canabal A, et al. PNAS. 2021;118(48):e2102178118. · source

"Despite non-competitive binding kinetics, SR-17018-mediated MOR activation is fully reversible by naloxone in cellular and animal assays. Naloxone is the appropriate response to a suspected SR-17018 overdose."
— Multiple studies — see SR17.org/safety for the full reference list. · source

"SR-17018 produces dependence in mice, with rewarding effects in conditioned place preference and a clear withdrawal syndrome on discontinuation."
— Kudla L, Bugno R, Podlewska S, et al. Pharmaceutics. 2022;14(1):55. · source

"In rhesus monkey IV self-administration under a progressive-ratio schedule, SR-17018 had lower reinforcing strength than heroin and was comparable to buprenorphine."
— Ko M-C et al. The Journal of Pain. 2023. · source

"SR-17018 has been detected in the unregulated opioid supply alongside related orphine-class analogs since 2023. CFSRE and similar bodies have issued public alerts."
— Center for Forensic Science Research and Education, public alerts on novel synthetic opioids. · source

"SR-17018 does not appear on standard hospital or workplace immunoassay opioid panels. Forensic confirmation generally requires LC–MS/MS or LC–HRMS with appropriate reference standards."
— SR17.org/detection (with CFSRE primary sources). · source

Reporter talking points

Why this compound is in the news now

SR-17018 began appearing in the unregulated opioid supply in 2023 and has been the subject of growing online community interest since 2024 — driven primarily by self-reports describing it as a self-administered taper aid for people dependent on fentanyl, nitazenes, and other high-potency synthetic opioids. It is not approved for any human use anywhere in the world.

The 'biased agonism' story

SR-17018 was developed in 2017 to test whether selectively activating one of the μ-opioid receptor's two signaling pathways could produce pain relief without the dangerous side effects (especially respiratory depression) that make opioid overdoses fatal. Three follow-up studies (Gillis 2020, Fritzwanker 2021, Stahl 2021) have substantially complicated this hypothesis. The best current characterization is 'atypical, non-competitive, partial-agonist-like.'

Real risk picture

Oral SR-17018 produces respiratory depression in mice. The compound produces dependence and withdrawal in animals. People using it report withdrawal-like symptoms on discontinuation. Combining with other CNS depressants (benzodiazepines, alcohol, gabapentinoids, other opioids) is the most-cited fatal pattern with any opioid. Naloxone reverses an SR-17018 overdose, but repeat doses may be needed because SR-17018 can outlast a single naloxone dose.

What community use looks like

Public self-reports describe a calibration phase (2–3 days), maintenance phase (4–7 days), and taper phase (7–14 days). Doses range from ~25 mg every 6–8 hours for low-tolerance users to ~100–250 mg multiple times daily for high-tolerance users coming off fentanyl or nitazenes. None of this is clinically validated. SR17.org documents these patterns with strong disclaimers; the evidence-based equivalents are buprenorphine and methadone via licensed clinicians.

What's actually being sold

Material sold as SR-17018 in unregulated channels can contain other compounds — including significantly more dangerous ones such as nitazenes or fentanyl analogs. SR17.org is launching an independent third-party testing program: vendor-purchased and user-submitted samples will be sent for LC–MS/MS identity confirmation and a full adulterant panel, with results published openly.

Expert contact

For interviews, fact-checking, or background:

Editorial inquiries — submit through the tip form with "press inquiry" in the message; we respond within 24 hours.
Subject-matter consultation — pharmacology, analytical chemistry, regulatory background, or harm reduction. Tell us what you're working on and we'll route to the right reviewer.
Lab-testing program — for stories on the vendor-sampling program and analytical methodology, see /testing.

A direct press email will be published on this page on launch of the v1 byline.

Logos & screenshots

The SR17.org logo is available as an SVG at /icon.svg. Please don't crop, recolor, or alter it. Screenshots of the site for editorial use are fine without prior permission, with attribution.

Embargo & sourcing policy

We don't publish under embargo.
We are happy to be cited as a primary source for our own analysis and editorial framing, and as an aggregator for primary literature (link directly to the underlying paper where possible).
If you are running a piece on SR-17018 community use, we strongly prefer that you don't link to vendors or marketplaces, and that you do link to /safety or SAMHSA so readers in distress have an exit ramp.
If you find a factual error in something we've published, the submission form reaches an editor within hours; we will correct on the public changelog.

Previous coverage

A list of stories that have cited SR17.org will be maintained here as the site is quoted in print and broadcast. If you've covered the compound and want to add your piece, send us a link via the tip form.