As of July 18, 2026, Endomorphin-1 is legal to sell at retail in Wisconsin. Unscheduled - legal as research-use-only; no operative instrument reaches a structurally-dissimilar opioid peptide. Controlling source: Wis. Stat. 961.01(4m) (controlled substance analog; CONJUNCTIVE; effect prong includes 'narcotic').
Verified July 18, 2026 · confidence: confirmedEndomorphin-1 (Tyr-Pro-Trp-Phe-NH2) is not named or scheduled in Wisconsin. The state has a controlled-substance analogue statute whose similarity test is CONJUNCTIVE (chemical structure substantially similar to a scheduled substance AND a substantially similar CNS effect). The structure prong fails for a tetrapeptide, so the statute does not reach EM-1. Controlling instrument reviewed: Wis. Stat. 961.01(4m) (controlled substance analog; CONJUNCTIVE; effect prong includes 'narcotic'). Conclusion: no operative instrument reaches a structurally-dissimilar endogenous opioid peptide; status LEGAL at the state controlled-substances level. Residual risk: low. Federal floor still applies (Analogue Act human-consumption contingency + FD&C unapproved-new-drug).
Wis. Stat. 961.01(4m)(a): "'Controlled substance analog' means a substance the chemical structure of which is substantially similar to the chemical structure of a controlled substance included in schedule I or II AND: 1. Which has a stimulant, depressant, narcotic or hallucinogenic effect on the central nervous system substantially similar to ...; or 2. ... which the individual represents or intends to have [such effect] ..." (b) excludes controlled substances, approved-new-drug, and investigational substances. [Conjunctive - mandatory structure prong fails for a peptide despite the 'narcotic' effect term.]
Among Wisconsin's 4 neighbors, Illinois, Iowa, Michigan and Minnesota are legal, the same posture as Wisconsin.
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Not federally scheduled. Endomorphin-1 - not federally scheduled; endogenous opioid tetrapeptide, no CSA entry and no analogue-act structural hook Federal detail
2 instruments on file for this compound's framework in Wisconsin; 2 of 2 citations above are official sources. Each text carries its source and a fingerprint that changes when the law does.
3a1ed7bf79fb18f5**§ 961.14(4) (hallucinogen chapeau)** — "(4) Hallucinogenic substances. Any material, compound, mixture or preparation which contains any quantity of any of the following hallucinogenic substances, including any of their salts, isomers, esters, ethers, and salts of isomers, esters, or ethers that are theoretically possible within the specific chemical designation, in any form contained in a plant, obtained from a plant, or chemically synthesized:" — Wis. Stat. § 961.14(4), https://docs.legis.wisconsin.gov/document/statutes/961.14(4) (OFFICIAL — Wisconsin Legislature). Psilocin (s) and Psilocybin (r) are listed; 4-HO-MET is not, and there is no substituted-tryptamine class. **§ 961.01(12g) (isomer definition — narrows the catch-all)** — "'Isomer' means an optical isomer, but … in ss. 961.14(2)(nd) and (4) and 961.18(2m) 'isomer' includes any positional or geometric isomer." — Wis. Stat. § 961.01(12g), https://codes.findlaw.com/wi/controlled-substances-ch-961/wi-st-961-01/ (MIRROR: FindLaw). A homolog is neither positional nor geometric, so 4-HO-MET falls outside the class. **§ 961.01(4m)(a) (controlled substance analog)** — "'Controlled substance analog' means a substance the chemical structure of which is substantially similar to the chemical structure of a controlled substance included in schedule I or II and: 1. Which has a stimulant, depressant, narcotic or hallucinogenic effect on the central nervous system substantially similar to … a controlled substance included in schedule I or II; or 2. With respect to a particular individual, which the individual represents or intends to have [such effect] …" — Wis. Stat. § 961.01(4m)(a), https://codes.findlaw.com/wi/controlled-substances-ch-961/wi-st-961-01/ (MIRROR: FindLaw).
0a7fd287ab38c917961.25 Controlled substance analog treated as a schedule I substance. A controlled substance analog, to the extent it is intended for human consumption, shall be treated, for the purposes of this chapter, as a substance included in schedule I, unless a different treatment is specifically provided. No later than 60 days after the commencement of a prosecution concerning a controlled substance analog, the district attorney shall provide the controlled substances board with information relevant to emergency scheduling under s. 961.11 (4m). After a final determination by the controlled substances board that the controlled substance analog should not be scheduled, no prosecution relating to that substance as a controlled substance analog may be commenced or continued. 961.01 (4m) (a) "Controlled substance analog" means a substance the chemical structure of which is substantially similar to the chemical structure of a controlled substance included in schedule I or II and: 1. Which has a stimulant, depressant, narcotic or hallucinogenic effect on the central nervous system substantially similar to the stimulant, depressant, narcotic or hallucinogenic effect on the central nervous system of a controlled substance included in schedule I or II; or 2. With respect to a particular individual, which the individual represents or intends to have a stimulant, depressant, narcotic or hallucinogenic effect on the central nervous system substantially similar to the stimulant, depressant, narcotic or hallucinogenic effect on the central nervous system of a controlled substance included in schedule I or II.
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