Prostanozol is a designer anabolic-androgenic steroid. Chemically, it is stanozolol (the steroid sold as Winstrol) without the 17α-methyl group. It was first synthesized and tested in rats in 1961, but it was never developed or approved as a medicine.
In the mid-2000s it reappeared in “dietary supplements” sold online for muscle building, as a tetrahydropyranyl (THP) ether with a label name that hid its relationship to known steroids. The single most important fact: no controlled human trial of prostanozol has ever been published. What is known in people comes from a handful of single-volunteer urine studies done for anti-doping testing. The DEA placed it in Schedule III in 2012.
This page summarizes what regulators, rat studies and anti-doping laboratories report. It is for education only and is not medical advice.
| Property | Detail |
|---|---|
| Drug class | Designer anabolic-androgenic steroid (DHT-type skeleton with a fused pyrazole ring) |
| Other names | Prostanazol; 17β-hydroxy-5α-androstano[3,2-c]pyrazole; 17-desmethylstanozolol; sold as its 17-THP ether |
| Approval | Never approved as a drug; DEA knows of no legitimate medical use |
| Route | Oral (as sold in supplement products) |
| Studied human doses | No clinical trials; one published excretion study gave a single 100 mg dose to one man |
| Half-life | No published human pharmacokinetic data |
| Key structural fact | Same as stanozolol except it lacks the 17α-methyl group |
| US status | Schedule III anabolic steroid since August 29, 2012, including its salts, esters and ethers |
| WADA status | Prohibited at all times (S1.1 anabolic androgenic steroids), named on the list |
What it is
The DEA describes prostanozol (17β-hydroxy-5α-androstano[3,2-c]pyrazole) as testosterone with two changes: a pyrazole ring fused across carbons 2 and 3 of the steroid skeleton in place of the 3-keto group, and no double bond between carbons 4 and 5 (DEA final rule, 2012). The DEA also noted that its structure differs from stanozolol only by the missing 17α-methyl group.
| Feature | Prostanozol | Stanozolol |
|---|---|---|
| Pyrazole ring fused to the A-ring | Yes | Yes |
| 5α-reduced (DHT-type) skeleton | Yes | Yes |
| 17α-methyl group | No | Yes |
The stanozolol page explains what the 17α-methyl group does for oral activity and liver risk. Whether prostanozol, without that group, is meaningfully active when swallowed has never been measured in people.
The THP ether in supplement products
Products sold as “Prostanozol” around 2005 were labeled as containing 25 mg of “[3,2-c]pyrazole-5α-etioallocholane-17β-tetrahydropyranol.” The Australian anti-doping laboratory suggested this naming was “presumably in an effort to hide its relationship to androstane” (Kazlauskas, Recent Advances in Doping Analysis 2006). When the lab isolated the contents of one product, it found both the THP ether and the free 17-hydroxy steroid. The THP ether broke down readily to the free steroid, even in methanol.
This explains a naming difference between regulators:
- WADA lists prostanozol by the chemical name of the THP ether, 17β-[(tetrahydropyran-2-yl)oxy]-1’H-pyrazolo[3,4:2,3]-5α-androstane (WADA 2026 Prohibited List). PubChem also files the name “prostanozol” under the THP ether, formula C₂₅H₃₈N₂O₂, molecular weight 398.6 g/mol (PubChem).
- The DEA defines prostanozol as the free 17β-hydroxy steroid, and its rule covers that steroid’s salts, esters and ethers, so the THP ether is controlled too (DEA final rule, 2012).
Animal and receptor data
All potency data come from rats and laboratory assays, as summarized by the DEA (DEA final rule, 2012):
- 1961 synthesis paper (Clinton et al.). In rats given the drug by subcutaneous injection, compared with testosterone propionate, the ratio of anabolic activity (nitrogen balance) to androgenic activity (ventral prostate weight) was reported as eight.
- DEA-commissioned rat study. In castrated male rats, injected prostanozol prevented shrinkage of the ventral prostate, seminal vesicles and levator ani muscle. Tissue weight gains were comparable with testosterone.
- Receptor assays. Prostanozol bound the androgen receptor about as well as testosterone and activated it somewhat more strongly in a transactivation assay. It showed low binding and little or no activation at estrogen, progesterone and glucocorticoid receptors.
- Binding protein. One study reported about the same relative binding affinity for human sex steroid binding protein as testosterone.
About the anabolic:androgenic ratio. Prostanozol is often described online as a mostly anabolic steroid. The only ratio on record is the 1961 figure of eight, measured in rats given injections, not in people taking capsules. The later DEA-commissioned rat study found prostate and seminal vesicle effects comparable with testosterone. In other words, in the only controlled data that exist, prostanozol is clearly androgenic as well as anabolic.
How it behaves in the body
No study has measured prostanozol blood levels, bioavailability or half-life in humans, so any half-life quoted online is unsupported. What is known comes from anti-doping metabolism work, summarized below.
| Study | Model | Main findings |
|---|---|---|
| Kazlauskas, 2006 | 1 male volunteer, single 100 mg dose, urine collected for 48 h | Four urinary metabolites, all with a 17-keto group; hydroxylation proposed at the 3’, 4 and 16 positions, with the 16β-hydroxy-17-keto metabolite confirmed against a reference compound |
| Rodchenkov et al., 2006 | Healthy male volunteers (supplement product) | Oxidation of the 17-hydroxy group plus hydroxylation; three main metabolites, structures proposed from mass spectra only |
| Yum et al., Anal Sci Technol 2011 | Urine from women who had taken prostanozol | Eight metabolites, including 17-keto-prostanozol and several hydroxylated forms; three described as new; most excreted as glucuronide conjugates, some unconjugated, two as sulfates |
| Geldof et al., Steroids 2016 | Human liver microsomes and chimeric mice with human liver cells | 24 metabolites in two groups (17-hydroxy and 17-keto); main sites of change C-3’, C-4 and C-16; two newly described metabolites confirmed in a real positive doping sample |
The Belgian authors noted that ethical objections limit giving designer steroids to human volunteers, which is why they used laboratory models instead (Geldof et al., 2016). Both 2006 studies identified the metabolites partly by analogy with stanozolol’s known hydroxylated metabolites, and the Australian lab extracted them with its routine stanozolol confirmation method.
These studies show that prostanozol is absorbed and extensively metabolized after a dose. They do not show how much reaches the androgen receptor, for how long, or with what effect.
Regulatory status
Prostanozol was never submitted for approval as a drug. In its scheduling rule, the DEA said it was not aware of any legitimate medical use or New Drug Application, and could not identify any chemical manufacturer using it as an intermediate (DEA final rule, 2012).
| Date | Event |
|---|---|
| 1961 | Synthesis and rat anabolic/androgenic data published (Clinton et al.) |
| 2004–2005 | Supplement products labeled as a “pyrazole-etioallocholane” THP ether sold online and analyzed by anti-doping laboratories |
| July 2009 | FDA warning about bodybuilding products with steroid or steroid-like substances named a product containing the THP ether of prostanozol |
| March 2010 | DEA had identified 13 dietary supplements claiming to contain prostanozol, sold online |
| November 23, 2011 | DEA proposed classifying prostanozol and methasterone as Schedule III anabolic steroids |
| August 29, 2012 | Final rule took effect; prostanozol and its salts, esters and ethers became Schedule III |
Sources: DEA proposed rule, 2011; DEA final rule, 2012; Kazlauskas, 2006. Prostanozol is listed by name in the Schedule III anabolic steroid list (21 CFR 1308.13). It was scheduled in the same rule as methasterone, the steroid in Superdrol.
In sport, prostanozol is named under S1.1 anabolic androgenic steroids, prohibited both in and out of competition (WADA 2026 Prohibited List).
What the research shows
No human efficacy data
There are no randomized or controlled human trials of prostanozol for muscle mass, strength, body fat or any medical condition. Claims about how much muscle or strength it builds come from marketing and user reports, not from studies. The only controlled data on its anabolic effect are the rat assays described above.
A 2015 review of designer steroids sold as supplements, which lists prostanozol among them, makes the general point: little is known about the pharmacology of these unapproved steroids “due to the absence of clinical studies” (Joseph and Parr, Curr Neuropharmacol 2015).
No published case reports
A PubMed search for prostanozol (October 2026) returns only the metabolism study, the DEA rule and one review of supplement contamination. We found no published case reports of liver, kidney or other injury attributed specifically to prostanozol. This is not evidence that it is safe. It reflects how little anyone has studied it, and how often designer-steroid products contain different or additional steroids than the label says.
Side effects and risks
What can and cannot be said
No study has measured prostanozol’s effects on testosterone, LH, FSH, sperm, cholesterol, blood pressure or liver tests in people. Any statement about its side effects in humans is therefore an inference from its pharmacology, not a measurement.
Class effects of anabolic steroids
In receptor and rat studies, prostanozol acts as an androgen comparable with testosterone. The DEA lists the class effects of anabolic steroid misuse (DEA final rule, 2012):
- in men: testicular atrophy, decreased sperm count and sterility;
- in women and girls: deepening of the voice, increased facial and body hair, menstrual irregularities and clitoral enlargement, which can be permanent;
- in both sexes: liver damage and raised cholesterol, which may increase the risk of stroke and heart attack;
- in adolescents: stunted growth from early closure of the growth plates;
- psychological effects such as aggression, dependence, and depression on stopping after long-term use.
These are class-level expectations, not prostanozol-specific measurements.
Liver
Because prostanozol lacks the 17α-methyl group, it is sometimes assumed to be easier on the liver than stanozolol. No study has tested that in people, and no liver data of any kind exist for prostanozol. The DEA lists liver damage among the risks of anabolic steroid misuse in general.
Product quality
Prostanozol belongs to the wave of designer steroids sold through the supplement market:
- Hidden labeling. Products used chemical names such as “pyrazole-etioallocholane-tetrahydropyranol” instead of a recognizable steroid name (Kazlauskas, 2006).
- Supplement market. Doping-control researchers reported that designer steroids such as prostanozol and methasterone had been offered on the nutritional supplement market since 2002. They warned that cross-contamination of other supplements with these steroids was expected, creating a risk of unintended positive doping tests (Geyer et al., J Mass Spectrom 2008).
- Detection in sport. Prostanozol metabolites have been confirmed in a real positive doping-control sample (Geldof et al., 2016).
Key takeaways
- Stanozolol minus one methyl group. Prostanozol is 17-desmethyl stanozolol, a designer steroid first made in 1961 and never approved as a medicine.
- No human trials. Its effects on muscle, hormones and organs have never been measured in a controlled human study, and its human half-life is unknown.
- The ratio is from rats. The only anabolic:androgenic figure, eight, comes from 1961 rat injection studies. Later rat studies found androgenic effects comparable with testosterone.
- Sold as a disguised THP ether. Supplement products labeled it with obscure chemical names; the THP ether breaks down readily to the free steroid.
- Controlled and banned. It has been a US Schedule III anabolic steroid since 2012, ethers included, and WADA prohibits it at all times.
- Detectable in doping tests. Anti-doping labs have mapped its urinary metabolites, and they have been found in real athlete samples.
Sources
- Drug Enforcement Administration. Classification of two steroids, prostanozol and methasterone, as Schedule III anabolic steroids under the Controlled Substances Act. Final rule. Federal Register. July 30, 2012;77(146):44456–44462 (FR Doc 2012-18495). govinfo.
- Drug Enforcement Administration. Classification of two steroids, prostanozol and methasterone, as Schedule III anabolic steroids under the Controlled Substances Act. Notice of proposed rulemaking. Federal Register. November 23, 2011;76:72355 (FR Doc 2011-30081). govinfo.
- 21 CFR 1308.13. Schedule III. eCFR.
- World Anti-Doping Agency. The 2026 Prohibited List. In effect January 1, 2026. WADA 2026 Prohibited List.
- National Center for Biotechnology Information. PubChem Compound Summary for CID 56842253, Prostanozol. PubChem.
- Kazlauskas R. Miscellaneous projects in sports drug testing at the National Measurement Institute, Australia, 2005. In: Schänzer W, Geyer H, Gotzmann A, Mareck U, eds. Recent Advances in Doping Analysis (14). Cologne: Sport und Buch Strauss; 2006:129–140. PDF.
- Rodchenkov G, Sobolevsky T, Sizoi V. New designer anabolic steroids from Internet. In: Schänzer W, Geyer H, Gotzmann A, Mareck U, eds. Recent Advances in Doping Analysis (14). Cologne: Sport und Buch Strauss; 2006:141–150. PDF.
- Yum TW, Paeng KJ, Kim YJ. Determination of metabolites of prostanozol in human urine by LC/ESI/MS and GC/TOF-MS. Anal Sci Technol. 2011;24(3):173–182. DOI.
- Geldof L, Lootens L, Decroix L, et al. Metabolic studies of prostanozol with the uPA-SCID chimeric mouse model and human liver microsomes. Steroids. 2016;107:139–148. PubMed.
- Geyer H, Parr MK, Koehler K, et al. Nutritional supplements cross-contaminated and faked with doping substances. J Mass Spectrom. 2008;43(7):892–902. PubMed.
- Joseph JF, Parr MK. Synthetic androgens as designer supplements. Curr Neuropharmacol. 2015;13(1):89–100. PubMed.