Description
Methyltrenbolone (Metribolone, M3, R1881) is the 17α-methylated variant of Trenbolone. Structurally the compound is a 19-nor steroid with the Trenbolone-typical double bonds plus 17α-methyl group for oral bioavailability. In biochemical research R1881 is used as standard ligand for androgen receptor binding studies.
Per study reports Methyltrenbolone binds with extreme affinity to the androgen receptor - higher than any other known anabolic. Anabolic potency per milligram is correspondingly high, as is hepatotoxicity. The substance was never developed for human use.
In recreational research practice Methyltrenbolone is practically unusable due to extreme toxicity. A few designer steroid manufacturers in the 2000s tried to market M3 as a prohormone supplement, with dramatic hepatotoxicity case reports as a result. The substance has been explicitly banned in the US since 2014 under the Designer Anabolic Steroid Control Act.
The only sensible application of the injectable Methyltrenbolone form is as chemical standard in doping analytics or in molecular biology AR binding assays.
Pharmacokinetically oral bioavailability is high due to 17α-methyl group. Half-life about 4-6 hours.
Known effects in the few use case reports: massive ALT/AST elevations after 1-2 weeks, cholestasis, hypertension, severe lipid profile worsening, pronounced HPG suppression. Effects are more dramatic than under classical Trenbolone esters due to the additional 17α-methyl group.
Methyltrenbolone is on the WADA banned list.
You can order Methyltrenbolone as an oily injection solution in 10-pack at 5mg/ml.
This information is for research and educational purposes only. No medical recommendations.
Risks & Safety
Methyltrenbolone is considered one of the most toxic anabolics overall - the effects described in the literature and in case reports are drastic, and the substance was never developed for human use.
Documented in studies and case reports:
- Extreme hepatotoxicity: the additional 17-alpha-methyl group makes the already potent Trenbolone molecule massively hepatotoxic. Strong ALT/AST elevations after just 1-2 weeks and cholestasis are documented.
- Progestagenic action: as a 19-nor compound there is a progestagenic residual action with prolactin-mediated effects, as described for all Trenbolone derivatives. No aromatization.
- Suppression of endogenous production: a pronounced HPG suppression is documented, and recovery after discontinuation requires classical PCT in the reports.
- Cardiovascular: the few use case reports describe hypertension and a severe worsening of the lipid profile. The effects are more dramatic than under classical Trenbolone esters.
Baseline bloodwork before, during and after a research protocol is strongly advised. This classification does not replace medical advice. Risk and responsibility for any actual use lie entirely with the buyer.
Studies
- Binding of [3H] methyltrienolone (R 1881) in rat prostate and human benign prostatic hypertrophy (BPH) - Steroids 1976: characterization of the high-affinity AR binding of R1881, which remains the reference ligand for androgen-receptor studies.
- The use of methyltrienolone in the measurement of the free and bound cytoplasmic receptors for dihydrotestosterone in benign hypertrophied human prostate - Journal of Steroid Biochemistry 1978: methodological establishment of R1881 as the standard in AR binding assays.
- Androgen Receptor Assay with [3H]Methyltrienolone (R1881) in the Presence of Progesterone Receptors - Endocrinology 1979: technical study on selective AR quantification using R1881.
- Methyltrienolone (R1881) is not aromatized by placental microsomes or rat hypothalamic homogenates - Journal of Steroid Biochemistry 1984: demonstrates that R1881 is not aromatized to estrogens - relevant for experimentally separating androgenic from estrogenic activity.
- The Synthetic Androgen Methyltrienolone (R1881) Acts as a Potent Antagonist of the Mineralocorticoid Receptor - Molecular Pharmacology 2007: characterizes a mineralocorticoid-receptor antagonistic off-target activity of R1881.
