Educational reference only. Informational material drawn from peer-reviewed literature. Not medical advice and not a recommendation to use, dose, or modify any therapy. Decisions about hormone therapy should be made with a qualified healthcare provider.
Overview
Overview
Methyltrienolone (also known as metribolone, M-Tren, or by its research designation R1881) is a synthetic anabolic-androgenic steroid (AAS) with a unique distinction: it is one of the most potent AAS ever synthesized, with reported potency of 120-300 times the oral anabolic potency and 60-70 times the androgenic potency of methyltestosterone in animal assays. It is also one of the most hepatotoxic AAS ever evaluated, so toxic that even at very low doses of ≤1 mg per day, it produces marked elevation of liver damage markers within two weeks, leading researchers to describe it as "the most hepatotoxic steroid at present" in the foundational toxicity study.
Methyltrienolone was synthesized in the 1960s by Roussel-Uclaf (the same French pharmaceutical company that developed trenbolone) as part of structure-activity research on highly potent androgens. Due to its extreme hepatotoxicity, the compound was never developed for human therapeutic use and has spent its primary commercial life as a research reagent, specifically as a radio-labeled tracer ([³H]methyltrienolone, often written [³H]R1881) widely used in androgen receptor binding studies in laboratories worldwide.
The compound has no injectable form in common use. All non-medical use is via oral administration.
Forms
Available forms & half-lives
| Form | Approximate half-life |
|---|---|
| Oral tablet (not esterified) | ~6–8 hours |
What it does
Main effects
- Exceptional androgen-receptor binding affinity: approximately 5× testosterone, among the highest of any known compound; the basis of its use as the standard radiolabeled ligand [³H]R1881 in laboratory AR research
- Extreme overall potency: reported 120–300× the oral anabolic potency and 60–70× the androgenic potency of methyltestosterone in animal assays
- No aromatization to estrogen: inherited from trenbolone's structural modifications
- Orally bioavailable via 17α-methyl modification (which is also the source of the extreme hepatic risk)
- Significant progesterone receptor activity (~208% relative to progesterone) and substantial glucocorticoid receptor binding (~26% relative to dexamethasone), uniquely promiscuous among AAS
What to watch for
Common side effects
- Extreme hepatotoxicity: the defining safety concern; documented at doses as low as 0.1–1.0 mg/day in the foundational 1966 Velluz study; effects develop within 2 weeks; described as "the most hepatotoxic steroid" of its era and grounds for terminating all therapeutic development
- Profound HPG axis suppression even at very low doses
- Severe lipid changes and cardiovascular risk: inferred from AAS class effects plus the compound's exceptional potency
- Prolactin elevation via progesterone receptor activity: likely sexual dysfunction similar to trenbolone
- Glucocorticoid-mediated effects: possible immune suppression, mood changes, HPA axis disruption (distinctive concern given GR binding; standard AAS management approaches do not address this)
- Severe acne and androgenic skin effects: likely dramatic given the high direct AR potency
- Aggressive scalp hair loss in genetically predisposed users; 5α-reductase inhibitors do not protect (not a substrate)
- Rapid, severe virilization in women: contraindicated for female use under any circumstances
- Underground / research-chemical-only supply: no legitimate pharmaceutical source; unregulated sources require institutional credentials and diversion violates those terms
Key facts
Key facts worth knowing
- Methyltrienolone is structurally trenbolone with an added 17α-methyl group, combining trenbolone's exceptional androgen receptor binding affinity with the oral bioavailability provided by 17α-alkylation. This combination produces a compound with extreme potency at the cost of extreme toxicity.
- The compound binds to the androgen receptor with approximately 5× higher affinity than testosterone, among the highest AR binding affinities of any known compound. This is why [³H]R1881 became the standard radiolabeled ligand for AR binding studies.
- Beyond AR activity, methyltrienolone also has significant progesterone receptor activity (208% relative to progesterone) and substantial glucocorticoid receptor binding (26% relative to dexamethasone), making it pharmacologically promiscuous in ways that contribute to its adverse effect profile.
- The compound's hepatotoxicity is dose-dependent and present at the lowest doses ever evaluated. The 1966 toxicity study found effective hepatotoxic doses between 0.1 and 1.0 mg per day, with liver damage markers rising within two weeks at the lowest dose it tested. Velluz L et al., Steroids 1966
- Despite being known since the 1960s and characterized as extremely toxic, methyltrienolone continues to be used in non-medical contexts. WADA testing identified 11 adverse analytical findings for methyltrienolone in 2008 alone, demonstrating continued use in competitive athletics. Thevis & Schänzer, J Steroid Biochem Mol Biol 2008
- No human clinical trials of methyltrienolone for therapeutic indications have ever been completed, because early hepatotoxicity findings ended all therapeutic development.
Legal status
Legal status
Schedule III controlled substance in the United States (DEA) by inclusion in the AAS class. No FDA approval; no current human therapeutic use anywhere. WADA-prohibited at all times in competitive sport.