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Research compound — not a dietary supplement
RU58841 is a research compound, not a regulated dietary supplement. It is sold for research or off-label use. The evidence below is largely preclinical (animal and in-vitro) or early-stage, so no evidence score is assigned. This page is provided for transparency and education — it is not a recommendation to use. Consult a qualified healthcare provider, and be aware that purity, dosing, and legal status vary by jurisdiction.
What the evidence says
Most RU58841 studies are mechanism or observational rather than RCTs that measure a clinical effect — keep findings provisional.
Most evidence is from mixed-quality studies published 1994–1998.
Based on 5 studies
Confidence
LowBy outcome
RU58841 has an evidence score of 3/10 — emerging evidence based on 5 indexed studies. A grey-market 'research chemical' sold online to hair-loss communities as a topical finasteride alternative — RU58841 (PSK-3841 / HMR-3841) is a non-steroidal androgen-receptor antagonist developed in the late 1980s–90s (Roussel-Uclaf) as a TOPICAL treatment for androgenetic alopecia and acne, designed to block DHT at the hair follicle locally without the systemic anti-androgen effects of oral drugs. The CRITICAL fact is the ABSENCE of evidence in people: development was abandoned, RU58841 was NEVER approved, and there are essentially NO published human clinical trials of it. The entire evidence base is PRECLINICAL — rodent and stumptail-macaque models, an ex-vivo study of human balding-scalp grafts maintained on nude mice, and in-vitro androgen-receptor pharmacology — showing local hair regrowth and AR blockade in animals/tissue, not proven benefit or safety in humans. It is sold as a powder or topical solution of unverified identity, purity and concentration, used off-label to avoid the systemic DHT suppression of finasteride. The honest harms are mostly UNKNOWNS: no human safety data, uncharacterised systemic absorption and endocrine effects with chronic use, grey-market identity/purity risk, and scalp irritation. It is NOT an approved medicine and NOT a dietary supplement. Informational, harm-reduction entry only — the responsible takeaway is that RU58841's benefit and safety in humans are unproven. Representative study: PMID 9636157.
Notable regimens that report including RU58841 — documented, not endorsed.
Last reviewed June 2026 · evidence from 5 studies · how we score
This information is for educational purposes only. It is not a substitute for professional medical advice. Always consult a qualified healthcare provider before starting, stopping, or changing any supplement or medication.
RU58841 (PSK-3841; HMR-3841) — an abandoned, NEVER-approved topical non-steroidal androgen-receptor antagonist with essentially NO published human clinical trials, sold today as a grey-market 'research chemical' for hair loss
A grey-market 'research chemical' sold online to hair-loss communities as a topical finasteride alternative — RU58841 (PSK-3841 / HMR-3841) is a non-steroidal androgen-receptor antagonist developed in the late 1980s–90s (Roussel-Uclaf) as a TOPICAL treatment for androgenetic alopecia and acne, designed to block DHT at the hair follicle locally without the systemic anti-androgen effects of oral drugs. The CRITICAL fact is the ABSENCE of evidence in people: development was abandoned, RU58841 was NEVER approved, and there are essentially NO published human clinical trials of it. The entire evidence base is PRECLINICAL — rodent and stumptail-macaque models, an ex-vivo study of human balding-scalp grafts maintained on nude mice, and in-vitro androgen-receptor pharmacology — showing local hair regrowth and AR blockade in animals/tissue, not proven benefit or safety in humans. It is sold as a powder or topical solution of unverified identity, purity and concentration, used off-label to avoid the systemic DHT suppression of finasteride. The honest harms are mostly UNKNOWNS: no human safety data, uncharacterised systemic absorption and endocrine effects with chronic use, grey-market identity/purity risk, and scalp irritation. It is NOT an approved medicine and NOT a dietary supplement. Informational, harm-reduction entry only — the responsible takeaway is that RU58841's benefit and safety in humans are unproven.
RU58841 (PSK-3841 / HMR-3841) is an abandoned, NEVER-approved topical non-steroidal androgen-receptor antagonist sold today as a grey-market 'research chemical' for hair loss. There are essentially NO published human clinical trials of it. The entire evidence base is PRECLINICAL: in-vitro androgen-receptor pharmacology (Battmann 1994; Pan 1998; Miyamoto 1998), rodent local-vs-systemic activity and pharmacokinetics (Battmann 1994; Cousty-Berlin 1994), the classic stumptail-macaque androgenetic-alopecia model (Pan 1998), and an ex-vivo study of human balding-scalp grafts on nude mice (De Brouwer 1997) — all showing local hair regrowth and AR blockade in animals/tissue, NOT proven human efficacy or safety. The same pharmacology shows it can act as a partial AR agonist with the coactivator ARA70 in some cell contexts (Miyamoto 1998), so its receptor behaviour is not uniformly benign. The dominant signal is therefore an ABSENCE of human efficacy or safety data, against a profile of grey-market identity/purity risk, uncharacterised chronic systemic absorption and endocrine effects, and scalp irritation — so the score sits low.
RU58841 — also known by the development codes PSK-3841 and HMR-3841 — is a non-steroidal androgen-receptor antagonist of the N-substituted aryl-hydantoin class, synthesized at the Centre de Recherches Roussel-Uclaf in the late 1980s and early 1990s.
It was deliberately engineered to be a TOPICAL anti-androgen: applied to the skin, it binds the androgen receptor in the hair follicle and sebaceous gland and blocks dihydrotestosterone (DHT) locally, with very low systemic anti-androgen activity because it is rapidly cleared and forms little of the systemically active N-desalkyl metabolite (RU56279).
The intended indications were the androgen-dependent skin disorders — androgenetic alopecia (male/female pattern hair loss), acne and hirsutism — the appeal being a follicle-level DHT blockade WITHOUT the systemic hormonal effects (lowered libido, mood, fertility) associated with oral anti-androgens like finasteride.
The honest description of its evidence base is that, in humans, it BARELY HAS ONE.
Development was abandoned and RU58841 was NEVER approved by any regulator, and there are essentially NO published human clinical trials of it — no randomized controlled trials, no approved indication anywhere, and no pharmacovigilance on the material people actually buy.
What exists is entirely PRECLINICAL: in-vitro pharmacology showing RU58841 binds the androgen receptor with high affinity and competitively suppresses DHT activation of the receptor (Battmann 1994; Pan 1998; Miyamoto 1998); rodent work mapping its local-versus-systemic activity and pharmacokinetics (Battmann 1994; Cousty-Berlin 1994); the classic stumptail-macaque model of androgenetic alopecia, where topical RU58841 increased hair density, thickness and length with no detected systemic effects (Pan 1998); and an ex-vivo study in which human balding-scalp grafts were maintained on testosterone-conditioned nude mice and topical 1% RU58841 significantly increased hair recycling and linear hair-growth rate versus vehicle (De Brouwer 1997).
RU58841 is a non-steroidal androgen-receptor antagonist that binds the androgen receptor in the hair follicle and sebaceous gland with high affinity and competitively suppresses dihydrotestosterone (DHT) activation of the receptor — the androgen signal that drives follicle miniaturisation in pattern hair loss. In-vitro it suppressed DHT activation of wild-type AR with potency comparable to hydroxyflutamide (Pan 1998; Battmann 1994). This mechanism is characterised in cells and animal tissue, not validated in human scalp by any clinical trial.
RU58841 was engineered to act at the application site and clear quickly: in rodents it produced potent local anti-androgen effects (flank-organ regression, follicle effects) at doses with little effect on deep accessory sex organs or testosterone, because it forms very little of the systemically active N-desalkyl metabolite RU56279 (Battmann 1994; Cousty-Berlin 1994). The intent was follicle-level DHT blockade WITHOUT the systemic hormonal effects of oral anti-androgens — but human systemic absorption over chronic daily scalp use is uncharacterised.
How RU58841 works — from molecular targets to health outcomes. Click an edge to see supporting research.This visualization is in beta — pathways are being refined and expanded.
Tap node to isolate • Pinch to zoom • Tap edge for research
There is no established or legitimate human dose. RU58841 is an abandoned, never-approved topical anti-androgen with no human clinical trials, no approval, and no pharmacovigilance — this library does NOT provide a dosing protocol. Hair-loss communities typically mix research-chemical powder into ethanol/propylene-glycol carriers and apply it to the scalp at vendor-suggested strengths (often quoted around a few percent), but these figures are unverified for a product of unknown identity and purity and are not supported by any human trial. The only quantitative reference points are PRECLINICAL: topical 1% RU58841 in ethanol on human balding-scalp grafts grown on nude mice (De Brouwer 1997) and microgram topical doses in hamster/rat models (Battmann 1994) — animal/ex-vivo research doses, NOT human recommendations.
Can be taken without food
| Form | Type |
|---|---|
| 🧴No human form is endorsed — RU58841 is an abandoned, never-approved topical anti-androgen with no approved or supplement form | Recommended |
There is no over-the-counter, supplement or prescription form of RU58841. Grey-market raw powder or pre-mixed topical solutions are of unverified identity, purity and concentration and are frequently sold 'not for human consumption'.
Minimum: 4 weeks
Optimal: 24 weeks
Cycling: Not required
Note: No human timing is endorsed. RU58841 is an abandoned, never-approved topical anti-androgen with no human trials, sold as a grey-market research chemical. Any framing here is harm-reduction only (clean dry scalp, patch-test for irritation); this library does not schedule its use.
Dose-response data unavailable. The current published research for RU58841 does not provide sufficient dose-specific outcome data to generate reliable dose-response curves.
Refer to the Dosage & Timing section above for recommended dose ranges based on available evidence.
There are essentially no published human clinical trials of RU58841 — development was abandoned and it was never approved, so there is no demonstrated hair-regrowth benefit and no safety profile in living people. The closest evidence is an ex-vivo study of human balding-scalp grafts grown on nude mice (De Brouwer 1997); everything else is rodent, macaque or in-vitro. Any 'it works' claim circulating in hair-loss communities is extrapolated from preclinical models, not proven in humans.
In the stumptail-macaque model of androgenetic alopecia, topical RU58841 increased hair density, thickness and length with no detected systemic effects (Pan 1998), and on human balding-scalp grafts maintained on testosterone-conditioned nude mice, topical 1% RU58841 significantly increased follicle recycling and linear hair-growth rate versus vehicle (De Brouwer 1997). This is the basis of its grey-market reputation — but it is ANIMAL/EX-VIVO evidence only and remains UNPROVEN in living humans, with no controlled human trial, and it comes bundled with the unknowns and risks below.
RU58841 is sold as raw powder or a pre-mixed topical solution of unverified identity, purity and strength, frequently labelled 'not for human consumption' to skirt regulation. What a buyer actually applies — and at what concentration in what carrier — is not assured, so even the preclinical dose-response cannot be relied on, and contaminants or mis-identification are real possibilities.
RU58841 was designed to stay local, but no study has characterised systemic absorption through the human scalp over months-to-years of daily application, nor any resulting endocrine effects. In-vitro it can also act as a partial androgen-receptor AGONIST in some cell contexts (Miyamoto 1998). The systemic and endocrine consequences of chronic human use are genuinely UNKNOWN and unmonitored.
The most concrete reported issue with grey-market topical RU58841 is local scalp irritation, redness or dryness — driven both by the compound and by the solvents (ethanol, propylene glycol) used to dissolve research-chemical powders. There is no human safety study to bound the frequency or severity of local reactions.
Avoid — RU58841 is unstudied in humans (preclinical evidence only), never approved, of unverified identity and concentration, and carries unknown systemic/endocrine risk plus scalp irritation. There is no human evidence of benefit.
Avoid entirely — an anti-androgen can interfere with normal male-fetal genital development; there is no human safety data and systemic scalp absorption is uncharacterised.
Avoid — RU58841's systemic anti-androgen (or context-dependent agonist) effects in humans are uncharacterised and unmonitored, and could interact unpredictably with hormonal therapy.
Avoid — the compound and its solvent carriers commonly cause local irritation, with no human safety study to bound the risk.
Stacking RU58841 with other anti-androgens compounds an unmeasured systemic anti-androgen burden; RU58841 has no human pharmacokinetic data, so the combined endocrine effect is uncharacterised and unpredictable.
Co-applying solvents and active topicals can increase skin penetration and irritation; how this alters RU58841 absorption (and any systemic exposure) is unknown for a grey-market product of uncertain concentration.
Tip: Driven by the compound and by solvent carriers (ethanol, propylene glycol). There is no human safety study to bound it; patch-test, and stop use if irritation develops. No human dosing exists to limit local reactions.
Tip: RU58841 was designed to stay local, but chronic systemic scalp absorption and any endocrine consequences are uncharacterised in humans. There is no monitoring of hormone levels in grey-market use; this risk cannot be quantified or managed.
Tip: Powder and pre-mixed solutions are of unverified identity, purity and strength. There is no way to confirm what is being applied; mis-identification, contamination or wrong concentration are real and unmanageable risks of a research-chemical supply.
The commonly studied dose of RU58841 is There is no established or legitimate human dose. RU58841 is an abandoned, never-approved topical anti-androgen with no human clinical trials, no approval, and no pharmacovigilance — this library does NOT provide a dosing protocol. Hair-loss communities typically mix research-chemical powder into ethanol/propylene-glycol carriers and apply it to the scalp at vendor-suggested strengths (often quoted around a few percent), but these figures are unverified for a product of unknown identity and purity and are not supported by any human trial. The only quantitative reference points are PRECLINICAL: topical 1% RU58841 in ethanol on human balding-scalp grafts grown on nude mice (De Brouwer 1997) and microgram topical doses in hamster/rat models (Battmann 1994) — animal/ex-vivo research doses, NOT human recommendations.. Individual needs vary — start at the lower end of the range and adjust based on how you respond.
Timing is flexible for RU58841 — consistent daily use matters more than the time of day. There is no human dosing protocol and no human use this library endorses; the compound is sandboxed from the stack timing optimizer.
RU58841 should be used with caution — talk to a healthcare provider before taking it. The most commonly reported side effects are scalp irritation, redness or dryness, unknown systemic anti-androgen / endocrine effects with chronic use, harm from unverified grey-market identity / purity / contaminants. Use caution if any of these apply to you: Any human use — RU58841 is an abandoned, NEVER-approved topical anti-androgen with no human clinical trials and a grey-market product of unverified identity, purity and concentration; it is NOT a dietary supplement and NOT an approved medicine; Anyone seeking it for hair loss, acne or hirsutism — there is no human evidence of benefit for RU58841, only preclinical (animal/ex-vivo) data, and an unknown human safety profile; Pregnancy and breastfeeding, and women who may become pregnant — an anti-androgen can interfere with the normal genital development of a male fetus; there is no human safety data, and systemic scalp absorption is uncharacterised.
Regulates the circadian clock to reduce sleep onset time — most effective at low doses (0.3-1mg) for jet lag and rhythm disorders.
That last study is the closest thing to human data — human follicles, but grafted onto mice, and the authors framed it as a result that 'encourage[s] a clinical trial' that, decades later, has not produced a published, approved human result.
Crucially, the same in-vitro pharmacology also shows RU58841 (like other antiandrogens) can act as a partial androgen-receptor AGONIST in the presence of the coactivator ARA70 in some cell contexts (Miyamoto 1998), a reminder that its receptor behaviour is context-dependent and not fully benign.
Today RU58841 is sold as a grey-market 'research chemical' — raw powder or pre-mixed topical solution in carriers like ethanol/propylene glycol — to hair-loss communities who use it as a topical finasteride alternative specifically to avoid systemic DHT suppression.
The harms are dominated by UNKNOWNS rather than documented events: there is no human safety data at all; systemic absorption through the scalp over months-to-years of daily use, and any resulting endocrine effects, are uncharacterised in people; the product's identity, purity and actual concentration are not assured; and the most concrete reported issue is local scalp irritation.
The evidence score sits low and the level is 'Emerging' precisely because the dominant signal is an ABSENCE — promising preclinical anti-alopecia activity but NO proof of efficacy or safety in humans, layered on grey-market quality risk.
This is an informational, harm-reduction entry: the responsible conclusion is that RU58841 is an abandoned, never-approved topical anti-androgen sold as a research chemical, not a supported intervention, and there is no human use this library endorses.
Because RU58841 is sold as an unregulated 'research chemical', the substance, its purity, and the actual concentration of the powder or topical solution are not assured, and there is no human dosing or safety reference to anchor use. Compounding this, in-vitro pharmacology shows RU58841 can act as a partial androgen-receptor AGONIST in the presence of the coactivator ARA70 in some cell contexts (Miyamoto 1998), so its receptor effect is context-dependent rather than a clean, predictable block.
An androgen-receptor antagonist of uncharacterised systemic exposure could oppose or interact with hormonal therapy; with no human data the interaction is unpredictable and unmonitored.