Metenolone enanthate (also spelled methenolone enanthate) is an injectable anabolic-androgenic steroid sold as Primobolan Depot. It is the slow-release ester of metenolone, a steroid built on the dihydrotestosterone (DHT) skeleton. It entered clinical use in Europe in the early 1960s for wasting conditions, recovery after surgery and some cancers.
It is not an FDA-approved drug in the US, where it is a Schedule III controlled substance. It is still authorized in some countries: in Spain, Bayer’s Primobolan Depot 100 mg has been authorized since 1961 and is listed as marketed (AEMPS registry), and its official product information (summary of product characteristics, or SmPC) is the main regulatory source for this page. Controlled trials in people are few, small and mostly decades old.
This page summarizes what the Spanish product information, the published clinical studies and regulators report. It is for education only and is not medical advice.
| Property | Detail |
|---|---|
| Drug class | Anabolic-androgenic steroid (androstane derivative), ATC code A14AA04 |
| Brand / authorization | Primobolan Depot (Bayer); authorized in Spain since 1961 |
| Route | Intramuscular injection only |
| Strength | 100 mg/mL ampoule in castor oil with benzyl benzoate |
| Labeled adult dose (Spain) | 100 mg every 2 weeks; every 3–4 weeks after a good initial response |
| Half-life | Not stated in the product information; peak levels 6–11 days after injection |
| Conversion to estrogen | None, per the product information |
| US status | Not FDA-approved; Schedule III controlled substance |
| WADA status | Prohibited at all times (class S1.1, anabolic androgenic steroids) |
What it is
Metenolone is 17β-hydroxy-1-methyl-5α-androst-1-en-3-one, the name used in the US controlled-substance schedule (21 CFR 1308.13). Compared with DHT (17β-hydroxy-5α-androstan-3-one), it has two changes in the A-ring:
| Change | What it does |
|---|---|
| Double bond between carbons 1 and 2 | Alters the A-ring next to the 3-keto group. |
| Methyl group at carbon 1 | Gives the molecule its name (“1-methyl”). It is not the 17α-methyl group that makes oral steroids such as oxandrolone or methandienone resistant to liver breakdown. |
The enanthate form adds a seven-carbon fatty acid (heptanoic, or enanthic, acid) to the 17β-hydroxyl group. This makes the molecule more fat-soluble so it releases slowly from an oil injection. The figures below come from PubChem (metenolone enanthate; metenolone):
| Form | Formula | Molecular weight | Share that is metenolone |
|---|---|---|---|
| Metenolone (free steroid) | C₂₀H₃₀O₂ | 302.5 g/mol | 100% |
| Metenolone enanthate | C₂₇H₄₂O₃ | 414.6 g/mol | ≈ 73% |
A 100 mg dose of the enanthate therefore delivers about 73 mg of metenolone. The same parent steroid is also sold as an acetate ester, which was used orally (see Primobolan (metenolone acetate) and oral Primobolan).
The earliest papers on the enanthate date from 1962: a study of its growth and body-composition effects in animals (Joechle and Langecker, Arzneimittelforschung 1962) and a clinical report on its use after surgery (Fixson, Med Welt 1962).
Receptor binding
Metenolone acts through the androgen receptor. In a 1984 study using rat and rabbit tissue, its binding to the androgen receptor ranked below nandrolone but above testosterone (Saartok et al., Endocrinology 1984). Two other findings from that study matter:
- Metenolone bound only weakly to sex hormone-binding globulin (SHBG), the blood protein that carries testosterone.
- For most steroids tested, binding in skeletal muscle and in the prostate was similar (a muscle-to-prostate ratio of about 0.4–1.7). Receptor binding alone did not show a muscle-selective “anabolic” steroid.
About anabolic:androgenic claims. The Spanish product information says metenolone’s anabolic effect exceeds its androgenic effect over a wide dose range, but it gives no ratio and cites no assay. Numerical ratios quoted online could not be traced to a primary source, so we do not repeat them here.
Pharmacokinetics
The Spanish SmPC gives the only regulatory pharmacokinetic data (AEMPS SmPC):
| Parameter | What the product information states |
|---|---|
| Bioavailability after IM injection | Complete (100%) |
| Release | Slow release from the injection site, then cleavage into metenolone and enanthic acid |
| Peak level | About 250 ng-equivalents/mL of metenolone plus metabolites |
| Time to peak | 6–11 days after injection |
| After the peak | Levels fall slowly |
| Excretion | About 80% of metabolites in urine, 20% in bile; no unchanged ester in urine |
| Estrogenic metabolites | None formed |
The SmPC does not state an elimination half-life, and we found no published human study that measured one. The label notes a measurable rise in protein synthesis (shown by lower nitrogen excretion) lasting more than two weeks after a single ampoule, which matches its every-2-to-4-week dosing schedule.
Metabolism and detection
Most human metabolism data come from the acetate ester, which releases the same metenolone. After a 50 mg oral dose of metenolone acetate in two men, researchers identified twelve urinary metabolites (Goudreault and Massé, J Steroid Biochem Mol Biol 1990):
- The main metabolite was 3α-hydroxy-1-methylen-5α-androstan-17-one.
- Unchanged metenolone was found in urine for up to 90 hours.
- It made up only 1.63% of the dose.
Anti-doping laboratories keep finding longer-lasting markers. Sulfated metabolites extended detection to up to 17 days in one excretion study (Albertsdóttir et al., Drug Test Anal 2020). In a single volunteer, one sulfated metabolite was detectable for up to 40 days after an oral dose (He et al., Steroids 2016).
Approved medical use
In Spain, Primobolan Depot is a prescription-only medicine. Its labeled indication is for diseases and conditions that need more protein synthesis or protection from catabolic (tissue-breakdown) processes (AEMPS SmPC), such as:
- wasting diseases;
- cachexia (severe weight and muscle loss);
- advanced carcinoma of the breast or female genital organs.
The label states that anabolic steroids are not indicated to boost muscle development in healthy people or to increase physical performance.
| Population | Labeled dose (Spain) |
|---|---|
| Adults | 100 mg IM every 2 weeks; after a good initial response, 100 mg every 3–4 weeks |
| Very thin women | No more than 50 mg every 2–3 weeks |
| Acute or severe protein deficit | 200 mg initially, then 100 mg weekly; maintenance every 2–4 weeks |
| Extreme cachexia (e.g. advanced breast cancer) | 100 mg every 1–2 weeks, or 200 mg every 2–3 weeks |
| Adolescents 15–18 years, over 50 kg | 50 mg every 2 weeks; before puberty is complete, a 4–6 week break after each 4-week course |
| Children | Should not be used |
In the US, a search of FDA’s Drugs@FDA data returned no metenolone product (openFDA). Metenolone, including its esters, is listed as a Schedule III anabolic steroid (21 CFR 1308.13(f)).
What the research shows
Muscle after stroke
The only modern controlled data on muscle come from two small Japanese stroke-rehabilitation studies. Both used 100 mg of metenolone enanthate IM once a week for 6 weeks.
In a randomized trial, 26 hemiplegic stroke patients in subacute rehabilitation received metenolone enanthate or no drug, without added specific training (Okamoto et al., Am J Phys Med Rehabil 2011). Thigh muscle cross-sectional area was measured by CT:
| Group | Affected leg | Unaffected leg |
|---|---|---|
| Control | +3.3% | +5.2% |
| Metenolone enanthate | +13.4% | +14.5% |
The difference between groups was significant. The largest gains were in patients with the lowest motor function at the start.
A second, nonrandomized open-label study assigned 25 inpatients to metenolone enanthate plus strength training of the non-paralyzed leg (n = 14) or training alone (n = 11) (Shimodozono et al., Int J Neurosci 2010):
- At 2 weeks, peak knee torque had risen significantly in 9 of 10 test conditions in the steroid group, against 1 of 10 in the controls.
- At 6 weeks, the counts were 8 of 10 and 5 of 10.
- The authors described the effect as a trend and reported no contraindications to treatment.
There are no controlled trials in healthy or trained adults.
Advanced breast cancer
Before modern hormonal therapies, metenolone enanthate was tested as androgen therapy for metastatic breast cancer, including by the US National Cancer Institute as NSC-64967 (Kennedy and Yarbro, Cancer 1968). Results from uncontrolled series:
| Study | Patients | Regimen | Result |
|---|---|---|---|
| Notter, Acta Radiol 1975 | 43 women (41 evaluable) | 400–1,200 mg/week for at least 3 months | Objective remission lasting over 3 months in 8 of 41; liver and brain metastases did not respond |
| Hartmann et al., Med Klin 1981 | 66 women (record review) | Metenolone, form not stated in the abstract | Remission in 26, lasting a mean 8.2 months; bone metastases responded better than visceral ones |
Notter judged it about as effective as testosterone propionate but less virilizing (causing fewer male-type changes). These were not randomized trials, and the doses were far above the labeled dose.
Anemia from bone marrow failure
Like other androgens, metenolone was used to stimulate red cell production in marrow failure:
- Aplastic anemia: in 26 patients treated with metenolone enanthate, failures were about as common as good or partial responses. Low platelet counts usually persisted, and at least two months of treatment were needed to judge the result (Krug, Z Gesamte Inn Med 1980).
- Refractory anemias: in 19 consecutive patients given metenolone (form not stated in the abstract), remissions occurred in 7, with no obvious gain in survival (Lockner, Acta Med Scand 1979).
Liver cirrhosis
In 15 patients with compensated cirrhosis, 200 mg/week for four weeks increased albumin turnover, most in those with the lowest turnover at the start (Knöbel and Becker, Z Gastroenterol 1975). There was no control group, and no clinical outcomes were reported.
Side effects and risks
Liver
Metenolone lacks the 17α-methyl group linked to liver injury in oral steroids, but the product information still carries liver warnings (AEMPS SmPC):
- Isolated, life-threatening bleeding into the abdomen has been seen with benign, and more rarely malignant, liver tumors after hormonal substances like this one.
- Severe upper-abdominal pain, an enlarged liver or signs of internal bleeding should prompt a check for a liver tumor.
- Liver function should be tested periodically. A clinically significant rise or new gallstones requires stopping the drug.
- Jaundice is listed as a side effect.
Cholesterol
In 28 postmenopausal women with metastatic breast cancer given metenolone enanthate, 12 developed raised blood lipids (hyperlipoproteinemia): 10 of type IIa and 2 of type IIb (Garbrecht et al., Dtsch Med Wochenschr 1981). One of the type IIb patients had a heart attack during treatment. The lipid changes did not track the dose and reversed in every case after stopping. The SmPC also lists high cholesterol among side effects.
Virilization in women
The product information warns that women sensitive to androgens can rarely develop acne, excess hair growth (hirsutism) and voice changes. Treatment should stop at the first sign of voice change (voice fatigue, hoarseness), because continued use can make the change permanent. The label specifically tells prescribers to warn women who use their voice professionally.
Other listed effects
The SmPC lists these side effects, more common at high doses and with long use:
- edema (fluid retention);
- nausea, vomiting and diarrhea;
- excitation and insomnia;
- high calcium and low white cell counts;
- early closure of growth plates and stunted growth in adolescents.
In women with advanced breast or genital cancer, the drug should be stopped if high blood calcium develops. In the 66-woman breast cancer series, treatment was stopped in four patients for cholestasis (blocked bile flow), pulmonary embolism or high calcium (Hartmann et al., 1981).
Hormone suppression and fertility
We found no controlled human study that measured LH, FSH or testosterone during metenolone enanthate treatment, so the size of its effect on the body’s own hormone production is not documented. This does not mean it is non-suppressive. In one case report, a bodybuilder with persistent azoospermia (no sperm in the semen) a year after stopping had used several steroids, metenolone enanthate among them, and recovered only with hCG and hMG treatment (Menon, Fertil Steril 2003).
Interactions
The SmPC lists three interactions:
- Anticoagulants: it may increase their effect, so patients on oral anticoagulants need close monitoring when starting or stopping.
- Diabetes drugs: doses of oral glucose-lowering drugs or insulin may need adjustment.
- Ciclosporin: methyltestosterone raises ciclosporin levels, and other androgens may do the same, raising kidney-toxicity risk.
It can also lower thyroxine-binding globulin, so total T4 falls while free thyroid hormone stays normal.
Who should not use it
The Spanish product information lists these contraindications:
- breast cancer in men;
- prostate cancer;
- severe liver or kidney failure;
- current or past liver tumors;
- pregnancy, because of the risk of virilizing a female fetus.
It also calls for caution in people with heart failure, coronary disease, a prior heart attack, high blood pressure, edema, epilepsy, migraine or an enlarged prostate with urinary obstruction.
Legal status and use outside medicine
- US: Schedule III anabolic steroid, including its esters (21 CFR 1308.13(f)). No FDA-approved product exists, so any metenolone enanthate sold in the US comes from outside the regulated drug supply.
- Sport: metenolone is named under S1.1 (anabolic androgenic steroids) on the 2026 Prohibited List, banned in and out of competition, according to the official Spanish publication of the list (BOE-A-2025-26460). The SmPC itself warns athletes that it can cause a positive doping test.
- Food residues: in an experiment, 50% of urine samples from men who ate chicken injected with methenolone heptanoate (another name for the enanthate) tested positive 24 hours later. Chicken fed the oral acetate caused no positives (Kicman et al., Clin Chem 1994).
Key takeaways
- A long-acting injectable DHT derivative. One 100 mg ampoule peaks 6–11 days after injection, and the label doses it every 2–4 weeks. No human half-life has been published.
- Does not form estrogen. The product information states that metenolone is not converted to estrogenic metabolites.
- Very little controlled human data. The best muscle data are two small 6-week stroke-rehabilitation studies at 100 mg/week, one randomized (n = 26), showing ≈ 13–15% thigh muscle growth vs 3–5% in controls.
- Not risk-free. The label warns of liver tumors with bleeding, jaundice and voice changes in women. In one series, 12 of 28 women developed raised blood lipids.
- “Mild” is not the same as tested. No study has measured how much it suppresses the body’s own testosterone.
- Controlled and banned. Schedule III and not FDA-approved in the US; prohibited at all times in sport.
Sources
- Agencia Española de Medicamentos y Productos Sanitarios (AEMPS). Primobolan Depot 100 mg solución inyectable: ficha técnica (summary of product characteristics), Bayer Hispania, text revised February 2016. AEMPS.
- Electronic Code of Federal Regulations. 21 CFR 1308.13, Schedule III, paragraph (f) Anabolic steroids. eCFR.
- US Food and Drug Administration. Drugs@FDA dataset, search for active ingredient methenolone. openFDA.
- Texto enmendado del Anexo I, Listas de sustancias y métodos prohibidos, de la Convención Internacional contra el dopaje en el deporte (2026 Prohibited List). Boletín Oficial del Estado. December 24, 2025 (BOE-A-2025-26460). BOE.
- National Center for Biotechnology Information. PubChem Compound Summary: metenolone enanthate (CID 248271). PubChem.
- National Center for Biotechnology Information. PubChem Compound Summary: metenolone (CID 3037705). PubChem.
- Joechle W, Langecker H. Biological effects of 1-methyl-delta1-androsten-17beta-ol-3-one 17-acetate and 17-enanthate (methenolone acetate and methenolone enanthate): growth stimulation, composition of animal body and enzyme metabolism [in German]. Arzneimittelforschung. 1962;12:218–223. PubMed.
- Fixson U. Methenolone enanthate (primobolan depot) in postoperative therapy [in German]. Med Welt. 1962;19:1109–1114. PubMed.
- Saartok T, Dahlberg E, Gustafsson JA. Relative binding affinity of anabolic-androgenic steroids: comparison of the binding to the androgen receptors in skeletal muscle and in prostate, as well as to sex hormone-binding globulin. Endocrinology. 1984;114(6):2100–2106. PubMed.
- Goudreault D, Massé R. Studies on anabolic steroids–4. Identification of new urinary metabolites of methenolone acetate (Primobolan) in human by gas chromatography/mass spectrometry. J Steroid Biochem Mol Biol. 1990;37(1):137–154. PubMed.
- Albertsdóttir AD, Van Gansbeke W, Coppieters G, et al. Searching for new long-term urinary metabolites of metenolone and drostanolone using gas chromatography-mass spectrometry with a focus on non-hydrolysed sulfates. Drug Test Anal. 2020;12(8):1041–1053. PubMed.
- He G, Yang S, Lu J, Xu Y. New long term metabolite in human urine for metenolone misuse by liquid chromatography quadrupole time-of-flight mass spectrometry. Steroids. 2016;105:1–11. PubMed.
- Okamoto S, Sonoda S, Tanino G, et al. Change in thigh muscle cross-sectional area through administration of an anabolic steroid during routine stroke rehabilitation in hemiplegic patients. Am J Phys Med Rehabil. 2011;90(2):106–111. PubMed.
- Shimodozono M, Kawahira K, Ogata A, et al. Addition of an anabolic steroid to strength training promotes muscle strength in the nonparetic lower limb of poststroke hemiplegia patients. Int J Neurosci. 2010;120(9):617–624. PubMed.
- Kennedy BJ, Yarbro JW. Effect of methenolone enanthate (NSC-64967) in advanced cancer of the breast. Cancer. 1968;21(2):197–201. PubMed.
- Notter G. Treatment of disseminated carcinoma of the breast by metenolone enanthate. Acta Radiol Ther Phys Biol. 1975;14(6):545–551. PubMed.
- Hartmann F, Pompecki R, Desaga U, et al. Anabolic therapy in metastatic breast cancer [in German]. Med Klin. 1981;76(24):689–691. PubMed.
- Krug K. Pathophysiology of aplastic anemia and its treatment with methenolone enanthate [in German]. Z Gesamte Inn Med. 1980;35(22):809–812. PubMed.
- Lockner D. Treatment of refractory anemias with methenolone. Acta Med Scand. 1979;205(1-2):97–101. PubMed.
- Knöbel H, Becker K. Effect of an anabolic steroid (methenolone enanthate) on the intra- and extravasal albumin pool in liver cirrhosis [in German]. Z Gastroenterol. 1975;13(6):583–587. PubMed.
- Garbrecht M, Lehmann U, O’Brien S, et al. Hyperlipoproteinaemia during additional methenolone administration in the treatment of metastasizing carcinoma of the breast [in German]. Dtsch Med Wochenschr. 1981;106(13):400–403. PubMed.
- Menon DK. Successful treatment of anabolic steroid-induced azoospermia with human chorionic gonadotropin and human menopausal gonadotropin. Fertil Steril. 2003;79(Suppl 3):1659–1661. PubMed.
- Kicman AT, Cowan DA, Myhre L, et al. Effect on sports drug tests of ingesting meat from steroid (methenolone)-treated livestock. Clin Chem. 1994;40(11 Pt 1):2084–2087. PubMed.
- Agencia Española de Medicamentos y Productos Sanitarios (AEMPS). CIMA registry record for Primobolan Depot 100 mg solución inyectable, registration number 36558 (authorization and marketing status). AEMPS.