Anabolic steroidAndrogen19-nortestosteroneResearch chemicalAnabolic steroidOral17-alpha-alkylated

Methyltrienolone (Oral, R1881)

Also known as Metribolone · R1881 · Methyltrienolone · M3 · 17a-methyl-trenbolone

Written by enwyReviewed 5 Aug 20261 sources0 comments

Methyltrienolone (metribolone, R1881; 17alpha-methyl-trenbolone) is an extraordinarily potent orally active 19-nor androgen used mainly as a laboratory radioligand for the androgen receptor. Its non-medical use is limited to tiny doses because of extreme hepatotoxicity; it has one of the highest anabolic/androgenic ratings on record but is regarded as one of the most liver-toxic AAS known.

01 Overview

Methyltrienolone is the 17-alpha-methylated form of trenbolone, which is otherwise not orally active. In research it is the standard high-affinity androgen-receptor ligand (R1881). Its potency is enormous, but 17-alpha-methylation of an already toxic trenbolone core produces severe, dose-limiting hepatotoxicity.

Non-medical use is confined to very small oral doses; even so, reports of rapid liver injury are common. It is non-aromatising but progestogenic. There are essentially no controlled human safety data supporting any use.

02 Mechanism

Extremely high-affinity androgen-receptor agonist (used as radioligand R1881); 17-alpha-methyl trenbolone core, non-aromatising, progestogenic.

03 Dosing

Tier	Dose	Route	Notes
Anecdotal micro-dose	500–1000 mcg/day	Oral	Micrograms; extreme hepatotoxicity limits any use.

Ester comparison

Ester	Half-life	Injection freq.	Testosterone by mass

04 Effects

Effect	Magnitude	Evidence
Dry strength/hardnessVery high potency reported at tiny doses.	marked per mg	Anecdotal
Increased aggressionStrong CNS androgenic effect.	marked	Anecdotal

05 Side effects

Effect	Severity	Frequency	Evidence
Progestogenic effectsLibido changes and possible nipple sensitivity.	Moderate	Common	Preclinical
HPTA suppressionProfound testosterone suppression.	Severe	Universal	Preclinical
Severe hepatotoxicityRapid and severe liver injury; among the most hepatotoxic AAS.	Life-threatening	Near-universal at any real dose	Observational

06 Legal status

United Kingdom

Class C

Anabolic steroid. · as of Jan 2026

United States

Schedule III controlled

Anabolic steroid. · as of Jan 2026

07 References

R1881 (methyltrienolone) as a reference androgen receptor ligandJournal of Steroid Biochemistry

08 Discussion0 comments

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This page is reference information, not medical advice. Doses and protocols are documented as they appear in the clinical literature and in practice — describing them is not a recommendation to use them. Countermeasures listed here are not a substitute for a physician. Legal status varies by jurisdiction and changes.