RU58841

RU58841 is an experimental topical anti-androgen that was studied for androgenetic alopecia, acne and hirsutism. During development it was known as RU58841, HMR3841 and PSK3841. In laboratory work it blocks dihydrotestosterone (DHT) from binding to the androgen receptor in the hair follicle.

The published evidence on whether it works is preclinical. Studies in hamsters (Battmann et al., 1994) and in the bald scalp of stumptailed macaques (Pan et al., 1998), and a study of balding human scalp grafts kept on mice (De Brouwer et al., 1997), showed anti-androgen effects. No human trial for hair loss has been published. Development stopped after early-phase (Phase II) human trials, and no results from those trials were released.

RU58841 is not approved as a medicine anywhere. It circulates only as an unregulated "research chemical", so its identity, purity and strength are unverified, and buying or importing it for personal use may be unlawful where you live.

The first human study (six men, one 30 mg scalp application) found RU58841 and one of its metabolites in the blood, which the authors describe as "considerable systemic exposure" (Okutan et al., 2026). That study did not look at side effects or long-term use. The long-term safety of RU58841 in people is unknown. As an anti-androgen that reaches the blood, it could affect sexual function and the breasts, and it could harm a developing male fetus, so anyone who is pregnant or could become pregnant should not use it.

Community views are mixed. Discussions cover whether it works, side effects that users report, and its unapproved status. These are individual accounts with unverified product, not trial data. Talk to a doctor or pharmacist before starting, stopping or combining any hair-loss treatment.