Methyltrienolone (Metribolone)
Methyltrienolone ('Metribolone', 'oral tren', R1881) is a 17α-methylated derivative of trenbolone and one of the most potent androgens known. Its extreme AR affinity and non-aromatising, non-5AR-reduced profile make it a benchmark androgen in laboratory research, but as a human drug it is regarded as extraordinarily hepatotoxic and toxic overall, used only at microgram doses if at all.
01 Overview
Methyltrienolone (R1881) is used widely in pharmacology as a high-affinity radioligand for the androgen receptor because of its exceptional potency and metabolic stability. Adding a 17α-methyl group to the already very potent trienolone skeleton makes it orally active but dramatically increases toxicity.
Recreational human use is rare and confined to microgram doses; it is often described as the most hepatotoxic oral steroid, with severe liver strain reported even at tiny doses. Because it does not aromatise or reduce, its effects are purely androgenic, and the risk profile is severe enough that it is generally considered unsuitable for human use. Data are essentially anecdotal.
02 Mechanism
Exceptionally high-affinity androgen-receptor agonist derived from trenbolone with 17α-methylation; does not aromatise or undergo 5α-reduction, giving pure, extremely potent androgenic activity.
03 Dosing
| Tier | Dose | Route | Notes |
|---|---|---|---|
| Threshold | 100–250 mcg/day | Oral | Microgram dosing only; extreme potency. |
| Common | 250–500 mcg/day | Oral | Even at these microgram doses toxicity is severe. |
| Heavy | 500–1000 mcg/day | Oral | Dangerous; considered unsuitable for human use. |
Ester comparison
| Ester | Half-life | Injection freq. | Testosterone by mass |
|---|
04 Effects
| Effect | Magnitude | Evidence | |
|---|---|---|---|
| Extreme strength and drivePronounced strength and aggression at microgram doses. | Anecdotal | ||
| Dry, hard appearanceNon-aromatising and non-reducing, so no water retention. | Anecdotal | ||
| Rapid onset of severe side effectsToxicity and malaise appear quickly, often outweighing any benefit. | Anecdotal |
05 Side effects
| Effect | Severity | Frequency | Evidence | Countermeasures |
|---|---|---|---|---|
| Severe adverse lipid and cardiovascular strainMarked HDL suppression and cardiovascular strain. | Severe | Very common | Anecdotal | |
| HPTA suppressionProfound suppression of endogenous testosterone. | Severe | Universal | Observational | |
| Extreme hepatotoxicityWidely regarded as the most hepatotoxic oral steroid; severe liver injury reported even at microgram doses. | Life-threatening | Very common | Observational |