RU-58841 — Research, Dosing & Price Guide

RU-58841 is a non-steroidal anti-androgen developed for topical treatment of androgenetic alopecia (male pattern baldness). It works by competitively binding to androgen receptors in the scalp, blocking the hair-miniaturizing effects of dihydrotestosterone (DHT) without systemic anti-androgenic effects. Though never brought to market, it remains one of the most discussed experimental hair loss treatments in the research community.

RU-58841 is a topical anti-androgen that competitively binds to the androgen receptor (AR) in hair follicle dermal papilla cells. DHT, converted from testosterone by 5-alpha-reductase, binds to these receptors and triggers a cascade of gene expression changes that shrink the hair follicle over successive growth cycles — a process called follicular miniaturization. RU-58841 occupies the AR binding site without activating the receptor's transcriptional activity, effectively acting as a silent blocker. Unlike systemic anti-androgens like finasteride (which inhibits DHT production) or spironolactone (which blocks AR systemically), RU-58841 is designed for topical application, limiting its activity to the scalp. Its short half-life in serum (if absorbed) further limits systemic exposure. In preclinical studies on stumptail macaques — a primate model that naturally develops pattern baldness — topical RU-58841 reversed hair follicle miniaturization and promoted regrowth comparable to or exceeding finasteride.

• A 1998 study in the Journal of Steroid Biochemistry and Molecular Biology showed RU-58841 reversed follicular miniaturization in stumptail macaques over 6 months
• Topical RU-58841 produced hair regrowth comparable to systemic finasteride in the macaque model without affecting serum DHT levels
• In vitro studies demonstrate high binding affinity for the androgen receptor with negligible agonist activity
• ProStrakan (now Kyowa Kirin) developed it through Phase I but discontinued development for commercial reasons, not safety concerns
• Anecdotal reports from the hair loss community suggest visible thickening within 3–6 months of consistent use
• No published human clinical trials exist — all clinical-grade evidence is preclinical

• Common research dose: 50 mg/mL solution applied topically to the scalp once daily
• Typical application volume: 1–2 mL per day (50–100 mg total)
• Dissolve in a vehicle of 70% ethanol / 30% propylene glycol for optimal penetration
• Apply to dry scalp, focusing on areas of thinning, ideally at bedtime
• Cycle: used continuously; effects may reverse upon discontinuation
• Some protocols alternate with minoxidil (RU-58841 at night, minoxidil in the morning)

Known Side Effects

• Scalp irritation, dryness, or flaking at the application site (common with alcohol-based vehicles)
• Contact dermatitis in individuals sensitive to the compound or vehicle ingredients
• Theoretical risk of systemic anti-androgenic effects if significant transdermal absorption occurs (reduced libido, erectile dysfunction), though not reported at standard topical doses
• Initial shedding ('dread shed') in the first 2–4 weeks as dormant follicles re-enter the growth cycle
• Long-term safety in humans is unknown due to lack of clinical trials

Safety Profile

RU-58841 was never approved for human use and has no completed human clinical trials. The primary safety concern is potential systemic absorption leading to anti-androgenic side effects, though its rapid degradation in serum (half-life of approximately 1 hour) provides a theoretical safety margin. Preclinical toxicology in the macaque model showed no significant systemic effects at topical doses. However, the compound is typically sourced from research chemical suppliers without pharmaceutical-grade quality control, introducing purity and contamination risks. Users should exercise caution with concentration and application area. It should not be used by women of childbearing potential due to theoretical teratogenic risks of anti-androgens. Liver and kidney function have not been formally assessed in human users.

Week 1–4: No visible changes. Some users experience an initial shedding phase as miniaturized hairs are pushed out by new growth. This is a positive sign but can be alarming. Week 4–8: Shedding typically resolves. Hair may feel slightly thicker at the base but no visible regrowth yet. Week 8–16: Gradual thickening of existing hairs becomes noticeable. Vellus (fine, unpigmented) hairs may appear in thinning areas. Week 16–24: More significant improvement in hair density and thickness. Best results are seen in early-stage thinning; advanced baldness responds less robustly. Ongoing: Continuous use is required to maintain results. Discontinuation leads to gradual reversal over 3–6 months.

Prices sourced from peptides.gg marketplace. Prices may vary.