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Muscle & performance

Primobolan Oral (Methenolone Acetate)

The oral primo variant - mild and clean, but dosed higher due to low bioavailability.

1 min read 13 sources

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White tablet bottle with a black TPD label on a white podium, next to it a glossy blue 3D steroid molecule in a bright lab, symbolic image for methenolone acetate
Compound approved · in Japan as a tablet

Summary

At a glance

Sources checked on 26 Oct 2026

Approved in Japan
>50 years

as a tablet, according to a 2024 case report for osteoporosis for more than 50 years6

Response with methenolone
11 of 15

anaemia from bone marrow failure, on top of the immune therapy ATG, without methenolone 4 of 155

Haemoglobin after 2 years
12.6 g/dL

single case, before 7.6 g/dL, together with darbepoetin6

Methenolone in urine
90 hours

after one oral dose, two volunteers, plus 12 metabolites8

Metabolite detectable
40 days

new urinary metabolite after oral methenolone, one volunteer9

  • Methenolone acetate is methenolone with a short acetate ester, taken as a tablet. Methenolone is a derivative of DHT with a methyl group on the first carbon and in a comparison study bound to the androgen receptor more strongly than testosterone.113
  • In Japan the tablet is approved as a prescription medicine, according to the prescribing information among other things for osteoporosis, severe wasting and anaemia from bone marrow failure.10
  • In a randomised study of 30 people with anaemia from bone marrow failure 11 of 15 responded with methenolone on top of immune therapy, without methenolone 4 of 15.5
  • The prescribing information lists liver damage and jaundice as serious side effects and one case report describes fatal liver failure. Methenolone was detectable in urine for up to 90 hours after one dose, one metabolite for up to 40 days.10789
  • The registry lists no trial of its own for methenolone acetate and ChEMBL gives phase 2. Everything here is the state of research, not a recommendation.1213
Profile

Updated June 2026

Class
DHT derivative

oral, NOT 17a-alkylated

Use
Oral

1-2x per day

Half-life
short

acetate

WADA
banned

anabolic

Sizes
25 mg

1 size in the shop

Contents 12 sections
  1. At a glance
  2. What is Primobolan Oral?
  3. How it works
  4. Use and dosing
  5. What the research shows
  6. Research status
  7. Side effects
  8. Storage
  9. Related compounds
  10. FAQ
  11. Glossary
  12. Sources

What is Primobolan Oral?

Primobolan Oral (Methenolone Acetate) is the oral variant of the mild DHT derivative methenolone. Unlike most oral steroids it is not 17a-alkylated but 1-methylated. Even so, it is not gentle on the liver: the Japanese prescribing information of the tablet warns of liver damage and jaundice. On top of that comes markedly lower oral bioavailability. It delivers the same clean, dry gains as the injection, just needing higher doses.

This information is for research and educational purposes only. No medical advice.

Comparison

Methenolone and relatives

Another form of the same compound and related steroids at the same receptor, as described in the TPD lexicon. Tap a card to open its entry.

Oral methenolone, 1-methylated Primobolan Oral (Methenolone Acetate) AR
Methenolone, long ester as an injection Primobolan E (Methenolone Enanthate) AR Oral 1-methylated DHT Proviron (Mesterolone) AR Oral DHT derivative Anavar (Oxandrolone) AR Oral testosterone with a 17α methyl group Methyltestosterone AR

In a comparison study methenolone bound to the androgen receptor more strongly than testosterone and mesterolone but less strongly than nandrolone. 3

How it works

Like injectable primobolan, the oral form mildly activates the androgen receptor, does not aromatize and causes no estrogen side effects. Due to low oral bioavailability less compound reaches the blood - hence the higher mg figures compared to 17a-alkylated orals.

Where it acts

Where methenolone acted in studies

Tap a point or a card. Colour = target, grey = observed, partly only in single cases.

  1. Skeletal muscle

    Binds to the androgen receptor in muscle more strongly than testosterone (rat and rabbit)3

    AR
  2. Blood formation

    Response in 11 of 15 people with anaemia from bone marrow failure, on top of ATG5

    Observed in trials
  3. Bone

    Loss of bone density slowed, a single case6

    Observed in trials
  4. Liver

    Fatal liver failure in a frail patient, a single case7

    Observed in trials
  5. Testes and hormone axis

    Anabolic steroids suppress own hormone production, sometimes for months2

    Observed in trials

Known targets3

Compound CHEMBL2106880: one described target, Binding, stronger than testosterone (muscle and prostate, rat and rabbit).

Androgen receptor
Gene
AR
UniProt
P10275
ChEMBL
CHEMBL1871
Action
Binding, stronger than testosterone (muscle and prostate, rat and rabbit)
Glossy blue 3D steroid molecules on light glassy muscle fibres, on the left a transparent honeycomb band with a molecule passing through it
Methenolone binds to the androgen receptor. Symbolic image.

Use and dosing

Dosing

Dosing, titration and syringe

Loading the dosing information …

  • Getting started and stepping up, drawn as a staircase
  • Units on the U-100 syringe for every step
  • How long one vial lasts
White tablet bottle with a black TPD label on a bright table, next to it five white tablets in a row
Symbolic image.

What the research shows

Methenolone has historical clinical use in anemia and muscle wasting. The AAS pharmacology (Kicman 2008, Hartgens & Kuipers 2004) classes it as a mild, non-aromatizing DHT derivative.

Study results

What the trials measured

Interactive: switch tabs, tap points, show or hide arms. Arms are named relative to each other, no dosing advice.

Anaemia from bone marrow failure5

30 people, randomly assigned, all with the immune therapy ATG

Response5 11 of 15 vs 4 of 15
Immune therapy ATG alone 26.7%
ATG plus oral methenolone 73.3%
Survival5 difference not statistically significant
Immune therapy ATG alone 43.0%
ATG plus oral methenolone 87.0%

Response calculated from the numbers in the abstract, the abstract gives 31% for the group without methenolone. According to the authors the side effects of ATG and androgens were considerable but manageable. An American study found no benefit of the combination.

Haemoglobin in an older man with MDS6

Anaemia from myelodysplastic syndrome and kidney disease

Before start6 1 month before
Before treatment (single case) 7.6 g/dl
After 1 month6
On methenolone acetate and darbepoetin (single case) 9.1 g/dl
After 2 years6
On methenolone acetate and darbepoetin (single case) 12.6 g/dl

A single patient, together with darbepoetin (stimulates blood formation). According to the authors liver values and PSA stayed normal.

Bone density per year in the same case6

Change before and during treatment

Lumbar spine6
Before treatment (single case) -4.4%
On methenolone acetate and darbepoetin (single case) -2.9%
Right femoral neck6
Before treatment (single case) -8.3%
On methenolone acetate and darbepoetin (single case) +1.1%
Left femoral neck6
Before treatment (single case) -8.1%
On methenolone acetate and darbepoetin (single case) -0.2%

Values from the table in the full text. A single case without a comparison group, the authors cannot prove a causal link.

Glass sculpture of a forearm with visible muscle strands in a glass case on a white plinth, in a bright exhibition room
Research on methenolone in humans. Symbolic image.

Research status

Where the research stands

ClinicalTrials.gov lists no trial of its own for methenolone acetate. Listed are an analysis of Japanese claims data with methenolone and a study that names the methenolone enanthate injection among many substances. As of 26 Oct 2026. 12

  1. Preclinical Structure at the membrane receptor GPR133
  2. Phase 1 no registered trial
  3. Phase 2 no registered trial
  4. Phase 3 no registered trial
  5. Approval in Japan as a tablet
Approved in Japan as a prescription tablet, according to the prescribing information for osteoporosis, severe wasting (for example in chronic kidney disease, cancer, injuries and burns) and anaemia from bone marrow failure. ChEMBL lists the compound with phase 2.10
Show all 2 trials on a timelineHide timeline 1 completed 1 running 0 with results
Without phase

Bar: start to primary endpoint (planned for running trials). Green = completed, blue = progress until 26 Oct 2026.

Side effects

  • Liver: even without 17a alkylation the Japanese prescribing information lists liver damage and jaundice as serious side effects (frequency unknown) and requires regular liver tests with longer use. A case report describes fatal liver failure in a frail 75-year-old (Tsukamoto 1993).
  • Androgenic (DHT derivative) - hair loss possible in predisposed individuals.
  • HPTA suppression - PCT topic.
  • No estrogen side effects.

Storage

Store dry and cool, protected from light. Out of reach of children.

Three white tablet bottles and a folded light blue towel on a white shelf
Dry, cool and protected from light. Symbolic image.

Related

Related compounds

Same receptors or blends with Primobolan Oral (Methenolone Acetate): all in the TPD lexicon.

Primobolan Oral (Methenolone Acetate)
Primobolan E (Methenolone Enanthate) The same compound as an injection with a long ester Proviron (Mesterolone) Also 1-methylated, bound more weakly to the receptor Anavar (Oxandrolone) Oral DHT derivative DHB Oral (1-Testosterone) Another oral steroid Methyltestosterone Oral steroid with a 17α methyl group Masteron P (Drostanolone Propionate) Another DHT derivative, as an injection Deca (Nandrolone Decanoate) Bound more strongly to the receptor in experiments

FAQ

Common questions about Primobolan Oral (Methenolone Acetate)

Short answers, each backed by the sources below.

What is methenolone acetate?

Methenolone is a steroid derived from DHT with a methyl group on the first carbon. As the acetate it is taken as a tablet, unlike the injection with the long enanthate ester. In a comparison study methenolone bound to the androgen receptor in muscle and prostate more strongly than testosterone but less strongly than nandrolone.113

Is methenolone acetate approved?

Yes, in Japan as a prescription tablet. The Japanese prescribing information names osteoporosis, severe wasting in chronic kidney disease, cancer, injuries and burns as well as anaemia from bone marrow failure. ChEMBL lists the compound with phase 2 and ClinicalTrials.gov lists no trial of its own (as of 26 October 2026). Everything here is the state of research, not a recommendation.101312

What do human studies show?

In a 1988 study 30 people with anaemia from bone marrow failure received the immune therapy ATG, half of them randomly also oral methenolone. With methenolone 11 of 15 responded, without it 4 of 15. A 2024 case report describes an older man whose haemoglobin rose and whose bone density declined more slowly on methenolone acetate and darbepoetin.56

Does the tablet strain the liver?

Methenolone does not carry a 17α methyl group like many other oral steroids. Even so, the Japanese prescribing information lists liver damage and jaundice as serious side effects and advises regular liver tests with longer use. A 1993 case report describes fatal liver failure in a frail 75-year-old. In studies of athletes a review found no liver damage from anabolic steroids.1072

Which side effects have been described?

The prescribing information lists hoarseness that may persist, more body hair, acne and menstrual changes in women. In men it lists acne and suppressed testicular function with large amounts over a long time. Reviews of anabolic steroids also describe suppressed own hormone production, falling HDL cholesterol and rising blood pressure.102

What does GPR133 have to do with methenolone?

GPR133 is a receptor in the cell membrane. A 2025 paper found that DHT activates it in muscle cells, the messenger cAMP rises and muscle strength increases. Using cryo-electron microscopy the authors also showed methenolone bound to this receptor. This is basic research, consequences for use have not been studied.4

How long is methenolone detectable?

After one oral dose of methenolone acetate researchers found 12 metabolites in two volunteers, methenolone itself was detectable in urine for up to 90 hours. A study from a doping laboratory later found a metabolite that was detectable for up to 40 days.89

Glossary

Terms explained briefly

Dotted words in the text open these explanations directly.

1-methylated
A methyl group sits on the first carbon of the steroid skeleton, not at position 17.
17α alkylation
A carbon group at position 17 protects many oral steroids from breakdown in the liver.
Acetate ester
Short acid chain on the compound. It is split off quickly in the body.
Anaemia from bone marrow failure
The bone marrow makes too few blood cells (aplastic anaemia). Androgens can stimulate blood formation.
Androgen receptor
Protein inside the cell that androgens bind to. Genes are then read, for example for muscle building.
ATG
Antithymocyte globulin, antibodies against immune cells. It dampens the immune response that attacks the bone marrow.
DHT
Dihydrotestosterone, a potent androgen. It is made from testosterone in the body and is not converted to oestrogen.
GPR133
Receptor in the cell membrane (gene ADGRD1). DHT activated it in muscle cells.
Hormone axis (HPTA)
Hypothalamus, pituitary and testes together control the body's own testosterone production. Androgens from outside suppress this axis.
Metabolite
Substance formed when the body converts a compound. Doping tests often look for long-lasting metabolites.

Evidence

Sources

Show all 13 sourcesHide sources 9 Studies1 Trial registry3 Database checked 26 Oct 2026

Studies

  1. Review of the pharmacology of anabolic steroids

    Kicman, British Journal of Pharmacology, 2008

    DOI 10.1038/bjp.2008.165 PMID 18500378
    Checked 26 Oct 2026 via doi.org, Crossref, PubMed
  2. Review: effects and side effects of anabolic steroids in athletes

    Hartgens und Kuipers, Sports Medicine, 2004

    DOI 10.2165/00007256-200434080-00003 PMID 15248788
    Checked 26 Oct 2026 via doi.org, Crossref, PubMed
  3. Binding of anabolic steroids to the androgen receptor in muscle and prostate

    Saartok et al., Endocrinology, 1984

    DOI 10.1210/endo-114-6-2100 PMID 6539197
    Checked 26 Oct 2026 via doi.org, Crossref, PubMed
  4. GPR133 as a membrane androgen receptor, structure with methenolone

    Yang et al., Cell, 2025

    DOI 10.1016/j.cell.2025.01.006 PMID 39884271
    Checked 26 Oct 2026 via doi.org, Crossref, PubMed
  5. ATG with or without oral methenolone in aplastic anaemia

    Kaltwasser et al., European Journal of Haematology, 1988

    DOI 10.1111/j.1600-0609.1988.tb00806.x PMID 3278927
    Checked 26 Oct 2026 via doi.org, Crossref, PubMed
  6. Case report: bone density on methenolone acetate in MDS

    Ushimaru et al., JCEM Case Reports, 2024

    DOI 10.1210/jcemcr/luae055 PMID 38623532
    Checked 26 Oct 2026 via doi.org, Crossref, PubMed, PubMed Central
  7. Case report: fatal liver failure after methenolone acetate

    Tsukamoto et al., Annals of Hematology, 1993

    DOI 10.1007/BF01709665 PMID 8334198
    Checked 26 Oct 2026 via doi.org, Crossref, PubMed
  8. Urinary metabolites of methenolone acetate in humans

    Goudreault und Massé, Journal of Steroid Biochemistry and Molecular Biology, 1990

    DOI 10.1016/0960-0760(90)90383-v PMID 2242348
    Checked 26 Oct 2026 via doi.org, Crossref, PubMed
  9. New long-term urinary metabolite of methenolone

    He et al., Steroids, 2016

    DOI 10.1016/j.steroids.2015.10.015 PMID 26519767
    Checked 26 Oct 2026 via doi.org, Crossref, PubMed

Trial registry

  1. Search on ClinicalTrials.gov

    ClinicalTrials.gov, U.S. National Library of Medicine

    Checked 26 Oct 2026 via ClinicalTrials.gov API v2

Database

  1. Japanese prescribing information for the methenolone acetate tablet

    KEGG MEDICUS, Fachinformation Stand August 2020

    Checked 26 Oct 2026 via KEGG MEDICUS
  2. Methenolone acetate in KEGG DRUG

    KEGG DRUG (D01375)

    Checked 26 Oct 2026 via KEGG REST API
  3. Methenolone acetate in ChEMBL

    ChEMBL, EMBL-EBI (CHEMBL2106880)

    Checked 26 Oct 2026 via ChEMBL

In the shop

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