Parabolan was the brand name of trenbolone hexahydrobenzylcarbonate, a long-acting injectable form of the synthetic anabolic-androgenic steroid (AAS) trenbolone. Unlike other trenbolone forms, it was sold as a prescription medicine for people. The French company Negma marketed it from 1971 until it was taken off the market in 1997, for wasting in older people, recovery from major surgery, extensive burns and pressure sores (BIAM record).
The single most important fact is that Negma’s Parabolan was discontinued in 1997, and no study of how this ester behaves in the body was ever published. It was never approved in the US. Trenbolone is otherwise approved only as an acetate implant for beef cattle (see Trenbolone Acetate). We found no current regulated pharmaceutical version; products sold as “Parabolan” today generally come from outside the regulated drug supply.
This page summarizes what the former French product record, chemical databases, regulators and the limited human data report. It is for education only and is not medical advice.
| Property | Detail |
|---|---|
| Drug class | Synthetic anabolic-androgenic steroid; carbonate ester of trenbolone, a 19-nor (estrane) steroid |
| Brand and maker | Parabolan (earlier name Hexabolan; code R 2580), Negma laboratories, France |
| Market history (France) | Approval published January 18, 1971; launched April 6, 1971; discontinued November 6, 1997 |
| Route and form | Deep intramuscular injection; 1.5 mL glass ampoule in peanut oil |
| Strength | 76 mg trenbolone hexahydrobenzylcarbonate per ampoule, equal to 50 mg trenbolone |
| Former labeled dose | One ampoule every 15 days for the first month, then one ampoule a month for 3 months |
| Formula and weight | C₂₆H₃₄O₄, 410.5 g/mol; ≈66% trenbolone by weight |
| Half-life | Not measured: no published pharmacokinetic study of this ester in humans or animals |
| US status | Never FDA-approved; trenbolone and its esters are Schedule III anabolic steroids |
| WADA status | Prohibited at all times (S1.1 anabolic androgenic steroids) |
What it is
Trenbolone’s chemical name is 17β-hydroxyestra-4,9,11-trien-3-one. Like nandrolone, it lacks the carbon-19 methyl group of testosterone, and it has three double bonds in its ring system. In Parabolan, a cyclohexylmethyl carbonate group is attached at the 17β position (PubChem CID 20055297). “Hexahydrobenzyl” is an older name for cyclohexylmethyl, so the same compound is also listed as trenbolone cyclohexylmethylcarbonate.
Strictly speaking, this is a carbonate rather than an ordinary carboxylic acid ester like the acetate or enanthate. As with other esters, the attached group has no hormonal role. It makes the molecule more fat-soluble, so it stays longer in the oil depot. The body has to remove it to release free 17β-trenbolone, the active hormone.
The table compares the trenbolone forms in this library, using PubChem’s computed fat-solubility score (XLogP3; higher means more fat-soluble):
| Form | Formula | Molecular weight | Trenbolone by weight | XLogP3 |
|---|---|---|---|---|
| Trenbolone (free hormone) | C₁₈H₂₂O₂ | 270.4 g/mol | 100% | 1.9 |
| Trenbolone acetate | C₂₀H₂₄O₃ | 312.4 g/mol | ≈87% | 2.5 |
| Trenbolone enanthate | C₂₅H₃₄O₃ | 382.5 g/mol | ≈71% | 4.9 |
| Trenbolone hexahydrobenzylcarbonate | C₂₆H₃₄O₄ | 410.5 g/mol | ≈66% | 5.2 |
Sources: PubChem CID 25015, CID 66359, CID 20112041 and CID 20055297. The weight ratio matches the French product record, which stated that 76 mg of the ester corresponds to 50 mg of trenbolone.
How it acts on receptors
Once released, the hormone is the same whichever ester was injected. In laboratory binding studies, 17β-trenbolone bound the recombinant human androgen receptor with an affinity similar to dihydrotestosterone (DHT). It also bound the bovine (cow) progesterone receptor slightly more strongly than progesterone itself, and its main metabolites had under 5% of its androgen receptor affinity (Bauer et al., APMIS 2000). A review describes its androgen receptor affinity as about three times that of testosterone (Yarrow et al., Steroids 2010).
Unlike testosterone, trenbolone is not converted to more potent androgens by 5α-reductase or to estradiol by aromatase; it is metabolized to weaker androgens instead. The receptor pharmacology is covered in more depth on the Trenbolone Acetate page.
Pharmacokinetics
No pharmacokinetic study of trenbolone hexahydrobenzylcarbonate has been published, in people or in animals. Its absorption rate, peak timing and half-life after injection are therefore unknown. Figures quoted online, such as a half-life of about two weeks, could not be traced to any measurement.
The only indirect clue is the former French dosing schedule, which spaced injections 15 days apart and then a month apart (BIAM record). That shows the product was designed as a long-acting depot. It does not establish a half-life.
What is known about the free hormone once it is released:
| Setting | Finding |
|---|---|
| Cows, IV trenbolone acetate | The ester was cleaved within minutes; free trenbolone left the blood with a half-life of 1.5 h |
| Human plasma, in vitro | Trenbolone bound mainly to albumin; about 4% was free |
| Total blood clearance | 17β-trenbolone cleared about twice as fast as testosterone |
| One human, oral radiolabeled 17β-trenbolone, 0.04 mg/kg | 54% of the dose in urine by 26 h and 63% by 72 h |
The cattle, in-vitro and clearance data come from the Joint FAO/WHO Expert Committee on Food Additives (JECFA) review (WHO Food Additives Series 23, 1988). The single human subject excreted mainly glucuronide conjugates of 17α-trenbolone, 17β-trenbolone and trendione (Spranger & Metzler, J Chromatogr 1991).
Former medical use
The French product record lists the following indications (BIAM record):
- cachexia (severe wasting) and undernutrition in older people;
- recovery after major surgery;
- extensive burns and pressure sores;
- proposed for some forms of osteoporosis in older people or caused by other drugs.
| Item | Former French labeling |
|---|---|
| Usual dose | One ampoule (76 mg) every 15 days for the first month (3 injections), then one ampoule a month for the next 3 months (3 injections) |
| Administration | Deep intramuscular injection |
| Dispensing | Pharmacy, prescription-only (List II) |
| Inactive ingredients | Benzyl alcohol, ethanol, neutralized peanut oil |
| Discontinued | November 6, 1997 |
The record does not state why the product was withdrawn. We found no published randomized trial of Parabolan for any of these uses, and no data showing how well it worked.
What the research shows
In people
There are no controlled human trials of trenbolone hexahydrobenzylcarbonate in the published literature indexed by PubMed. The only published human dosing study of any trenbolone form used the acetate ester: 5 or 10 mg intramuscularly every other day for 14 days (Krüskemper et al., Arzneimittelforschung 1967). As summarized by JECFA, the 5 mg dose produced nitrogen retention, and the 10 mg dose disturbed some women’s menstrual cycles (WHO Food Additives Series 23). No study has measured muscle, strength or body composition in people given trenbolone in any form.
In animals
The main efficacy data for trenbolone come from rats given the enanthate ester (Yarrow et al., AJP-Endo 2011). In castrated and intact rats, all doses increased an androgen-sensitive muscle by 35–40%, while low doses did not enlarge the prostate. These are results in rats and have not been tested in people. Details are on the Trenbolone Enanthate page.
Surveys of people who use trenbolone
Surveys do not separate the hexahydrobenzylcarbonate from other trenbolone esters. In the Global Drug Survey 2024, 237 men who had injected trenbolone in the past year reported more mood instability, irritability, depressive symptoms, and heart and liver concerns than 909 men using other AAS (all p under 0.001; small-to-moderate effect sizes) (Bonenti et al., Drug Alcohol Rev 2026). In a separate survey of 282 men using AAS, a higher trenbolone dose was associated with more verbal aggression (p = 0.045) (Piatkowski et al., Int J Drug Policy 2024). Both studies were self-reported and cross-sectional, so they cannot show that trenbolone caused these problems.
Side effects and risks
No controlled study has measured how often side effects occur with this ester. The best available sources are the former French product record, case reports and surveys.
Labeled warnings and side effects
The French record listed these adverse effects (BIAM record):
- Androgenic effects: virilization (masculinizing changes) with hirsutism (excess body and facial hair) and a hoarse voice, described as not reversible; also acne, oily skin, hair loss and increased libido.
- Anti-estrogenic effects in women: irregular periods, disturbed ovulation and absent periods.
- Metabolic effects: reduced glucose tolerance and raised triglycerides, especially with pre-existing high blood lipids.
The record warned that anabolic steroids keep testosterone-like activity and can cause irreversible androgenic effects, so prescribing should be carefully weighed. It advised caution in heart failure and kidney failure because of the risk of salt and water retention.
Who should not use it
The record listed these contraindications:
- children before puberty;
- young women, pregnancy and breastfeeding, because of the risk of virilizing the woman and the fetus;
- prostate cancer or benign prostate enlargement;
- liver failure, and chronic or recent hepatitis.
Liver
A Polish case report describes a 21-year-old bodybuilder who developed severe cholestasis (blocked bile flow), with bilirubin up to 65.5 mg/dL, after an overdose of a product called Parabolan (Anand et al., ASAIO J 2006). He needed five sessions of liver-support dialysis, and bilirubin was down to 2 mg/dL at 2 months. The case appeared years after the French product was discontinued, and the authors described the product as trenbolone acetate, so its actual contents are uncertain. A single case cannot prove cause or show how common this is.
Hormone suppression
Like other androgens, trenbolone suppresses the body’s own testosterone production. In rats, a weekly dose of trenbolone enanthate cut testosterone by 80% within 10 days (Yarrow et al., AJP-Endo 2011). No human data exist for the hexahydrobenzylcarbonate.
Product quality
With the French product gone, the ester is now found mainly in unregulated products. In a German analysis of 70 confiscated products, the declared contents differed from the actual contents in 18 (25.7%). Trenbolone and nandrolone esters in particular were often replaced or supplemented with testosterone derivatives (Thevis et al., J Anal Toxicol 2008). A product labeled “Parabolan” may therefore contain a different ester, a different steroid or a different dose.
Legal status and use outside medicine
- United States: trenbolone is named in Schedule III, and the listing covers its salts, esters and ethers (21 CFR 1308.13). FDA’s drug database has no approved human trenbolone product (Drugs@FDA).
- France: the only human product was discontinued in 1997.
- Sport: trenbolone is named in section S1.1 of the WADA 2026 Prohibited List, which also covers its esters. S1 substances are prohibited at all times, in and out of competition (WADA 2026 Prohibited List).
Key takeaways
- A discontinued French medicine. Parabolan was marketed by Negma in France from 1971 to 1997 as a prescription anabolic for wasting, surgery recovery and burns.
- A long-acting trenbolone depot. Each 76 mg ampoule delivered about 50 mg of trenbolone, given every 15 days and then monthly under the former label.
- The half-life is unknown. No pharmacokinetic study of this ester has been published, so quoted half-life figures are not evidence-based.
- Very little human evidence. There are no controlled trials of Parabolan; the human data on trenbolone come from one small 1967 study of the acetate, case reports and surveys.
- Labeled risks were androgenic and metabolic. The French record warned of irreversible virilization, menstrual disturbance, reduced glucose tolerance and raised triglycerides, and contraindicated it in liver disease and pregnancy.
- Today’s products are unregulated. Trenbolone and its esters are Schedule III in the US and banned at all times by WADA, and black-market contents often differ from the label.
Sources
- BIAM (Banque de Données Automatisée sur les Médicaments). PARABOLAN solution injectable (arrêt de commercialisation). Last updated November 19, 1999. BIAM (archived).
- National Center for Biotechnology Information. Trenbolone hexahydrobenzylcarbonate, PubChem CID 20055297; trenbolone, CID 25015; trenbolone acetate, CID 66359; trenbolone enanthate, CID 20112041. PubChem (hexahydrobenzylcarbonate); PubChem (trenbolone); PubChem (acetate); PubChem (enanthate).
- Bauer ER, Daxenberger A, Petri T, et al. Characterisation of the affinity of different anabolics and synthetic hormones to the human androgen receptor, human sex hormone binding globulin and to the bovine progestin receptor. APMIS. 2000;108(12):838–846. PubMed.
- Yarrow JF, McCoy SC, Borst SE. Tissue selectivity and potential clinical applications of trenbolone (17beta-hydroxyestra-4,9,11-trien-3-one): a potent anabolic steroid with reduced androgenic and estrogenic activity. Steroids. 2010;75(6):377–389. PubMed.
- Joint FAO/WHO Expert Committee on Food Additives. Trenbolone acetate. In: Toxicological Evaluation of Certain Veterinary Drug Residues in Food. WHO Food Additives Series 23. Geneva: World Health Organization; 1988. INCHEM.
- Spranger B, Metzler M. Disposition of 17 beta-trenbolone in humans. J Chromatogr. 1991;564(2):485–492. PubMed.
- Krüskemper HL, Morgner KD, Noell G. Clinical pharmacology of trienolones, a group of new anabolically actine aestrane-derivatives (4,9,11-oestratrien-17beta-ol-3-on) [in German]. Arzneimittelforschung. 1967;17(4):449–454. PubMed.
- Yarrow JF, Conover CF, McCoy SC, et al. 17β-Hydroxyestra-4,9,11-trien-3-one (trenbolone) exhibits tissue selective anabolic activity: effects on muscle, bone, adiposity, hemoglobin, and prostate. Am J Physiol Endocrinol Metab. 2011;300(4):E650–E660. PubMed; PMC.
- Bonenti B, Ahmadinejad B, Puljević C, et al. The Trenbolo(g)ne Sandwich: an international study comparing health harms among men who use anabolic-androgenic steroids with and without trenbolone. Drug Alcohol Rev. 2026;45(4):e70162. PubMed.
- Piatkowski T, De Andrade D, Neumann D, et al. Examining the association between trenbolone, psychological distress, and aggression among males who use anabolic-androgenic steroids. Int J Drug Policy. 2024;134:104636. PubMed.
- Anand JS, Chodorowski Z, Hajduk A, Waldman W. Cholestasis induced by parabolan successfully treated with the molecular adsorbent recirculating system. ASAIO J. 2006;52(1):117–118. PubMed.
- Thevis M, Schrader Y, Thomas A, et al. Analysis of confiscated black market drugs using chromatographic and mass spectrometric approaches. J Anal Toxicol. 2008;32(3):232–240. PubMed.
- Drug Enforcement Administration. 21 CFR 1308.13 Schedule III. Electronic Code of Federal Regulations. eCFR.
- Food and Drug Administration. Drugs@FDA: FDA-approved drugs. Drugs@FDA.
- World Anti-Doping Agency. The 2026 Prohibited List, in force January 1, 2026. WADA 2026 Prohibited List.