Clostebol
Active ingredient: Clostebol. 4-Chlorotestosterone, freely available in Italy as a wound ointment and therefore the most common cause of unintentional doping findings. Five milligrams on someone else's skin and a fleeting contact are enough for a positive sample. Never examined as a builder.
Auch bekannt als: 4-Chlortestosteron, Megagrisevit, Steranabol, Clostebolum
What it is
Clostebol is 4-chlorotestosterone: Testosterone with a chlorine atom at position 4. The molecular formula is C₁₉H₂₇ClO₂. It is usually administered as acetate.
Unlike most substances in this category, Clostebol is a common medicine, just not as a restorative: in Italy and some other countries it is available as an ointment and spray for wound treatment in every pharmacy under the name Trofodermin. It is precisely this wide availability that makes the substance what it is today: the best-investigated case of unintentional doping intake.
How it works
What the chlorine atom on C4 does
It does two things. Firstly, it blocks them aromatase, which would have to rebuild ring A; Clostebol does not produce estradiol. The same principle uses Turinabol, which also has a chlorine atom at this point.
Secondly, it hinders the 5-alpha reductase: The conversion that turns testosterone in the skin and prostate into the stronger dihydrotestosterone is impaired by the chlorine at C4. The substance is therefore not strengthened in the very tissues in which testosterone is. Combined with a weaker base effect, this results in the mild profile that Clostebol is known for.
A published binding measurement of Clostebol on Androgen receptor could not be found in the literature reviewed here. Why some derivatives have a stronger effect on the muscle than on the skin and prostate is not yet fully understood; A review article attributes it to the tissue-dependent control of the amount of receptors and to the metabolism within the cell.
What the studies show
There is nothing about the effect as a builder. No controlled examination, no dose determination, no measurement of strength or muscle mass. What there is in abundance concerns another question: how little is enough to attract attention in a doping control.
Five milligrams on someone else's skin
An Italian doping laboratory tested the question experimentally because the cases were increasing and those affected almost all stated that they had not taken the substance themselves. The result: After one single application of 5 mg clostebol acetate to the skin and a fleeting contact with the application site a positive doping result can be generated.
At the same time, the authors checked whether the route of absorption could be read in the urine. It can't be done: Neither the 5-alpha reductase, which is impaired by the chlorine atom, nor the sulfotransferases in the skin allowed a clear distinction between applied and swallowed or injected.
How far apart the numbers are
A systematic review summarized seven papers with a total of 32 people. The key metabolite 4-chloro-androst-4-en-3α-ol-17-one was present in the urine more indirect Absorption, i.e. mere contact, averages 0.5 nanograms per milliliter more direct Use at 8.1 nanograms per milliliter. The difference was statistically confirmed.
The scattering ranges overlap: up to 4.0 nanograms per milliliter for indirect contact versus 1.0 for direct contact. For each individual case, this means that no reliable assignment can be derived from a measured value alone. In terms of magnitude, it means that contamination typically produces significantly lower values than its own application. Both of these things together are the reason why such cases end up in court.
What the material does as a building agent remains an open question. For the substance class as a whole, a review article describes strength increases of around 5 to 20 percent of the initial value and 2 to 5 kg of body weight with short-term administration; Clostebol is considered weak within this class, without being measured.
Dosage
- There is no tested dose for construction. The medicinal application is an ointment on a wound, and the amount absorbed is so small that it is only noticeable analytically.
- For tested athletes, contact is already the problem. Five milligrams on someone else's skin and a fleeting contact are enough for a positive result. Anyone who competes in a tested sport needs to know whether anyone in the household uses such an ointment.
- The wound ointment is not a small-format rebuilding agent. Anyone who applies it to a large area in order to achieve an effect completely leaves the area for which the preparation is intended and examined.
- An aromatase inhibitor has no target here. Clostebol does not produce estradiol; it just lowers estradiol from other sources in the stack.
- Initial values before the first application. When used for restorative purposes, the same values apply as with any other androgen: blood pressure, lipid profile, Hematocrit, testosterone and LH.
Side effects
Your own axis
What happens: An supplied androgen drives the HPTA axis down, LH and FSH fall. Since Clostebol does not provide estradiol, androgen and estrogen fall at the same time unless otherwise stated.
What it depends on: Of dose and duration. A measurement of LH, FSH and testosterone under Clostebol could not be found; For this class of substances, the disorder can persist for months after discontinuation. What follows from this is: When used medicinally as a wound ointment, the amount absorbed is so small that suppression is not to be expected; This no longer applies when used with constructive intentions. What you can do: Determine testosterone and LH before starting and after stopping. For the restart HCG and Clomiphene the established means.
Blood lipids and blood pressure
What happens: For the substance class, a review article mentions increased blood pressure and reduced blood pressure HDL cholesterol together with its sub-factions as the significant risk changes. Since Clostebol does not aromatize, it also lacks estradiol, which has a beneficial effect on blood lipids in men.
What it depends on: Of dose and route of absorption. No figures specifically for Clostebol could be found in the literature reviewed. What follows from this is: The injected or applied route bypasses the first passage through the liver and is therefore expected to be more beneficial for blood lipids than a swallowed alkylated steroid; This has not been proven for this substance. What you can do: Lipid profile and blood pressure before the start and after four weeks, see Cardiovascular risks associated with AAS.
skin and hair
What happens: Androgens act on the sebaceous gland and hair follicles. With Clostebol, the conversion into the stronger dihydrotestosterone is impaired by the chlorine atom at C4, which is why acne and hair loss should be less severe than with testosterone.
What it depends on: About the predisposition and the dose. The expectation follows from the metabolic findings and is not measured as the frequency of side effects. What follows from this is: When used medicinally as an ointment, androgenic effects are not to be expected; when applied to large areas or sprayed. What you can do: An inhibitor of 5-alpha-reductase is of little help here because the conversion is hindered anyway. Local remedies and the dose remain.
The unintentional positive finding
What happens: This is the side effect with the most serious consequences for this substance, and it affects people who have never taken it. A single application of 5 mg on someone else's skin and a fleeting contact are sufficient for a positive doping result. The route of absorption cannot be determined with certainty in the urine.
What it depends on: From the proximity to the user and the timing. With indirect contact, the values were on average around sixteen times lower than with personal use, with overlapping scattering areas. What follows from this is: A low value indicates contamination but does not prove it, and a high value does not completely rule it out. What you can do: Anyone being tested should know which preparations are used in the household and in the cabin and, if in doubt, avoid contact with treated skin. After a finding, the measured concentration is the most important piece of information and should be included in every statement.
Classification
Clostebol is the substance where the interesting question is not what it does, but how little of it is enough to cause trouble. There is not a single study on it as a building material and it is considered weak within the substance class. As a freely available wound ointment, however, it is so widespread that it has become the most common cause of unintentional doping findings.
The numbers are unusually good. Five milligrams on someone else's skin and a fleeting contact are enough. With mere contact, the lead metabolite is on average 0.5 nanograms per milliliter, with personal use it is 8.1, and the scattering ranges overlap. This is exactly the constellation from which disputes arise: a clear difference in the average and no distinction in individual cases.
This results in little benefit and a concrete risk for strength training. If you are not tested, you have no reason to choose a weak substance without any effectiveness data. Anyone being tested has a reason to know the medicine cabinets in their area.
What's missing is exactly what the sports courts are asking for: a feature in the urine that reveals the route of absorption. The authors of the experimental work specifically looked for it and did not find any in the degradation pathways or in the sulfate compounds in the skin. As long as this remains the case, such cases are decided by the level of a single measured value, and this overlaps between guilt and chance.
Sources
- de la Torre X et al. Detection of clostebol in sports: Accidental doping? Drug Test Anal. 2020. PubMed
- Menditto VG et al. Clostebol detection after transdermal and transmucosal contact. A systematic review. Clin Chem Lab Med. 2025. PubMed
- Hartgens F, Kuipers H. Effects of androgenic-anabolic steroids in athletes. Sports Med. 2004. PubMed
- Kicman AT. Pharmacology of anabolic steroids. Br J Pharmacol. 2008. PubMed
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