RU-58841
Also known as: RU58841, PSK-3841, HMR-3841
Topical Anti-Androgen | Experimental Hair Loss Treatment
Overview
RU-58841 is a non-steroidal anti-androgen originally developed by Roussel Uclaf (later Hoechst Marion Roussel) in the 1970s-80s for topical treatment of androgen-dependent conditions including acne and androgenetic alopecia. It works by competitively binding to androgen receptors at the hair follicle, blocking the effects of dihydrotestosterone (DHT) locally without significantly reducing systemic androgen levels. Development was abandoned after Phase II clinical trials, and the compound was never submitted for regulatory approval. Despite this, RU-58841 has developed a substantial following in the hair loss community, where users source it as a raw research chemical and prepare their own topical solutions. Its extremely short systemic half-life means that even if absorbed through the skin, it is rapidly metabolized, limiting systemic anti-androgenic effects. However, the lack of completed clinical trials means its long-term safety profile remains unknown.
Key benefits
- Blocks DHT directly at the androgen receptor in hair follicles without reducing systemic DHT levels
- Extremely short systemic half-life limits risk of systemic anti-androgenic side effects
- Different mechanism of action from finasteride/dutasteride, allowing combination therapy
- Animal studies demonstrated significant hair regrowth in androgen-dependent alopecia models
- Topical application targets the site of action directly
- Does not interfere with systemic testosterone or DHT levels
Mechanism of action
RU-58841 functions as a competitive antagonist of the androgen receptor (AR). When applied topically to the scalp, it penetrates the skin and binds directly to androgen receptors in dermal papilla cells of hair follicles, preventing dihydrotestosterone (DHT) and testosterone from activating those receptors. This is fundamentally different from 5-alpha reductase inhibitors like finasteride, which reduce DHT production systemically. RU-58841 does not lower DHT or testosterone levels at all; it simply blocks their action at the receptor level in the tissue where it is applied. The compound has a very high binding affinity for the androgen receptor but an extremely short systemic half-life of roughly one hour due to rapid hydrolysis of its amide bond in the bloodstream. This pharmacokinetic profile is intentional: it confines the anti-androgenic activity to the scalp while minimizing the risk of systemic side effects such as sexual dysfunction or hormonal disruption. Animal studies in hamster flank organ and stumptail macaque models demonstrated significant local anti-androgenic effects, including hair regrowth and inhibition of androgen-dependent sebaceous gland activity, without measurable systemic anti-androgenic effects at therapeutic topical doses.
Molecular data
- Type
- Non-steroidal anti-androgen
- Half-life
- ~1 hour topically (very short systemic half-life)
Indications
What the research community uses this compound for, with self-reported effectiveness.
Hair Loss
Dosing protocols
Common protocols by delivery method. Adjust the curve below to model accumulation in your own cycle.
Delivery method
| Protocol | Dose | Frequency | Duration |
|---|---|---|---|
| — | 50mg (1mL of 50mg/mL solution) | Once daily | — |
| — | 25mg (1mL of 25mg/mL solution) | Once daily | — |
Safety
Reported adverse effects, contraindications, and what to monitor on cycle.
Common side effects
- Scalp irritation, dryness, or itching at the application site (often related to the vehicle/solvent rather than RU-58841 itself)
- Contact dermatitis in sensitive individuals
- Scalp flaking or peeling
Rare side effects
- Theoretical systemic anti-androgenic effects at high doses or with compromised skin barrier (reduced libido, fatigue)
- Headache reported by some users (unclear if causally related)
- Allergic reaction to the compound or vehicle components
Contraindications
- Women who are pregnant or may become pregnant (anti-androgens can cause feminization of a male fetus)
- Women who are breastfeeding
- Known hypersensitivity to RU-58841 or related non-steroidal anti-androgens
- Active scalp infections, open wounds, or severely compromised skin barrier on the scalp
- Individuals taking systemic anti-androgens (risk of additive anti-androgenic effects)
References
Primary literature and clinical-trial data informing this entry.