Mibolerone
Also known as: Cheque Drops, Cheque, Matenon, Dimethylnortestosterone, 7α,17α-Dimethyl-19-nortestosterone
Lower numbers = closer to natural. Higher numbers = more enhanced.
Why this rating?
Mibolerone is a synthetic, orally active and extremely potent anabolic-androgenic steroid, a 17α-alkylated 19-nortestosterone (nandrolone) derivative originally made as a veterinary drug. Receptor-binding studies are mixed on exactly how its androgen-receptor affinity compares to metribolone (one study found it higher, another found roughly half), but both are extremely potent, and mibolerone is used (recklessly) in microgram doses for a pre-contest aggression/hardness "edge" rather than for mass. The combination of extreme receptor potency, strong progestogenic activity and 17-alkylated liver toxicity puts it near the top of the scale, rated 9, just below the most toxic orals because it is a short-term drive compound, not a mass builder.
Overview
A veterinary anabolic steroid: marketed by Upjohn as "Cheque Drops" to prevent estrus (heat) in female dogs, that became an infamous pre-contest drug in bodybuilding. Extremely potent at the androgen receptor and taken in microgram doses, it is used almost entirely for a short-term aggression and hardness "psych-up" before lifting or stepping on stage, not to build muscle.
Important Warnings
- •A veterinary drug never approved for human use: the microgram doses cited are community/UGL-reported, not a clinical standard
- •One of the most androgen-receptor-potent oral steroids used in bodybuilding, active at microgram (not milligram) doses
- •17α-alkylated and hepatotoxic: liver enzymes can rise even from a single dose
- •Builds essentially no muscle mass, used only for an acute pre-event aggression/hardness effect, not as a cycle compound
- •Never combine with another 17α-alkylated oral (e.g. Halotestin, Anadrol, metribolone): hepatotoxicity compounds dangerously
- •The intense aggression it produces is itself a safety hazard, not just a side effect
Purpose & Use Cases
Veterinary Estrus Control (approved use)
Its actual approved indication: an oral treatment to prevent heat in adult female dogs, sold as Cheque Drops / Matenon.
Pre-Contest / Pre-Lift Aggression (reckless human use)
Some strength and physique athletes take microgram doses shortly before competing for a short burst of aggression and hardness, a practice defined by its risk, not its results.
Benefits
- Extreme androgen-receptor potency at microgram doses
- Short-lived aggression / drive "psych-up" before an event
- Some muscle hardness reported pre-contest
- Orally active
Good to Know
A dog drug used as a pre-contest "psych-up"
Mibolerone (Cheque Drops) was made by Upjohn to stop female dogs going into heat. Its human use has almost nothing to do with muscle growth, lifters and physique competitors take a microgram dose for a short, intense burst of aggression and hardness before a heavy attempt or the stage.
The aggression is the point, and the danger
Unlike most steroids, mibolerone is not run for weeks to build tissue; it is taken for its acute CNS/aggression effect. That same effect is what makes it hazardous. Intense irritability and impaired judgement are the reason for its reputation, not a side note.
A progestogenic 19-nor, not an estrogen problem
Like nandrolone and trenbolone, mibolerone barely touches the estrogen receptor (<0.1%) but strongly activates the progesterone receptor. So the hormonal side to watch with repeated use is prolactin/progestin-driven (libido, mood, erectile), an AI does nothing; a testosterone base and cabergoline are the relevant tools.
Extreme potency plus 17-alkylation = tiny toxic doses
It is dosed in micrograms because it is extremely AR-potent (studies differ on exactly how it compares to metribolone), and it is 17α-alkylated so it is hepatotoxic like every oral in that class. Tiny dose and short duration are not a sign of safety. They are a consequence of how potent and toxic it is.
Dosage Guidelines
| Experience Level | Dosage Range |
|---|---|
| Beginner | 0 – 0 mcg/day |
| Intermediate | 100 – 300 mcg/day |
| Advanced | 300 – 500 mcg/day |
There is no appropriate beginner dose. Human dosing is not medically established. The microgram ranges shown are community-reported pre-contest practice, not verified from a medical source. It is extremely potent and toxic; any use is high-risk and very short.
No formal human pharmacokinetic study exists; unverified community/UGL sources commonly describe an oral half-life of only a few hours, consistent with why it is taken as a single tiny dose shortly before an event.
Side Effects
Hepatotoxicity
very commonA 17α-alkylated oral, so it carries the liver strain of that class, elevated enzymes, cholestasis and worse with anything beyond very brief use.
The realistic mitigation is to avoid it or keep any use to a single tiny pre-event dose; TUDCA and bloodwork help but do not make it safe.
Severe Aggression / CNS Effects
very commonThe compound is used precisely for its intense aggression, which can spill into dangerous irritability, anxiety and poor judgement. This is a documented reason for its notoriety.
Recognise it as the intended (and risky) effect; not appropriate outside tightly controlled short use.
Progestogenic / Prolactin Sides
commonStrong progesterone-receptor activity (as a 19-nor) can raise prolactin and cause libido, mood and erectile problems with repeated use.
A testosterone base and cabergoline if prolactin rises; but repeated use is discouraged.
HPTA Suppression
very commonA potent androgen that suppresses natural testosterone; the concern is limited by how briefly it is used but still real.
Full PCT if used for more than a one-off dose.
Androgenic Effects (acne, hair loss)
commonHighly androgenic at the receptor, so acne and accelerated hair loss are possible in the predisposed.
As a 19-nor it is not a straightforward 5α-reductase story; finasteride is not a reliable fix.
General Mitigation Strategies
The honest mitigation is minimal use or none: mibolerone is a veterinary drug, not a human medicine, and is both extremely potent and hepatotoxic. If used at all it is a single microgram dose before an event, never a "cycle." A testosterone base and prolactin control address the progestogenic side, TUDCA and bloodwork address the liver, but none of this makes it safe. Its signature intense aggression is itself a safety hazard.
Support Supplements
Ancillary supplements commonly run alongside Mibolerone to manage side effects, support the target tissue, or fill nutrient demands it creates.
Cabergoline (dopamine agonist)
Controls prolactin elevation from mibolerone's strong progestogenic (19-nor) activity if it is used repeatedly.
- Dose
- 0.25 mg 2x/week, titrated to prolactin labs
- Timing
- With food
- When
- Only if bloodwork shows elevated prolactin.
Liver support (TUDCA + NAC)
KeyBaseline support against 17α-alkylated liver strain, necessary but far from sufficient for a compound this potent.
- Dose
- TUDCA 500-1,000 mg/day; NAC 600-1,200 mg/day
- Timing
- During any use
- When
- Does NOT make mibolerone safe; brevity and avoidance are the real protection.
Testosterone base
A 19-nor with strong progestogenic activity, so an androgenic base helps offset the "deca dick"-type sides if it is used more than once.
- Dose
- At least a replacement dose of testosterone
- Timing
- Throughout any repeated use
Post Cycle Therapy (PCT)
A single pre-event microgram dose is briefly suppressive; anything beyond that needs a standard SERM PCT (e.g. Nolvadex 40/40/20/20 mg/day). Because it is a progestogenic 19-nor, monitor prolactin alongside LH, FSH and testosterone in recovery. Realistically the dominant concern with mibolerone is its toxicity, not the recovery timeline.
How It Works
Mibolerone is a synthetic 17α-alkylated derivative of nandrolone (19-nortestosterone), first synthesised in 1963. It is an extremely potent agonist of the androgen receptor, though studies disagree on exactly how it compares to the related potent AAS metribolone. One comparison found mibolerone had higher AR affinity and selectivity, while another found it had only about half of metribolone's AR affinity despite similar progesterone-receptor binding. It has strong progestogenic activity in its own right (progesterone-receptor affinity ~214% vs AR ~108% of the reference ligand), with negligible estrogen-receptor binding (<0.1%). The 17α-methyl group makes it orally active and, as with all 17-alkylated orals, drives liver toxicity.
Hormonal & Androgenic Profile
Not a reliable numeric ratio: extremely AR-potent, though studies disagree on exactly how it compares to metribolone (one found higher AR affinity/selectivity, another found roughly half); progesterone-receptor affinity is strong (~214% vs AR ~108% of the reference ligand).
Estrogen-receptor binding is negligible (<0.1%) and it is not considered a meaningful aromatization substrate, so an AI is not the concern. Its estrogen-independent hormonal issue is progestogenic (prolactin), not estradiol.
A 19-nor (nandrolone-derived) steroid rather than a DHT-derivative, so the testosterone-to-DHT step that finasteride/dutasteride block is not central to its action. 5-AR inhibitors are not a reliable fix for its androgenic effects.
Expected to be harsh on lipids like other potent 17-alkylated orals; not well quantified because human use is brief and off-label. Progestogenic and androgenic strain rather than estrogenic water retention.
Fundamentals
Reference on the practices relevant to Mibolerone: how they are done and where they go wrong. Not a recommendation to use it.
Legal Status
Schedule III controlled substance (USA); Schedule IV (Canada). Approved only as a veterinary drug (never for human use).
Legal status varies by country and changes over time. This is a general summary, not legal advice.
WADA Status
Mibolerone is prohibited at all times as an exogenous anabolic androgenic steroid.