RU-58841 is a nonsteroidal antiandrogen: it blocks the androgen receptor, the target of testosterone and DHT. It was developed in the early 1990s as a topical treatment for acne, male-pattern hair loss and excess hair growth. It has never been approved as a medicine, and we found no published trial of it for hair growth in people.
Also known as: RU 58841, RU58841.
There is no approved product and no labeled strength. The only human study we found applied a single 30 mg dose to the scalp of six men to measure how the body handles it (Okutan, 2026); it did not test hair growth. That is a study protocol, not a recommendation.
RU-58841 is not an approved drug: there is no FDA-approved product, and it does not appear in Drugs@FDA. The evidence is mostly from the lab and animals. In hamsters (Battmann, 1994), small amounts applied to the skin shrank an androgen-dependent skin gland, without affecting deeper sex organs or testosterone levels at the doses tested. A 2005 lab study (Münster) built a prodrug, RU-58841-myristate, that skin and hair follicle cells convert back into RU-58841.
In the first human study of how the body handles it (Okutan, 2026), a single 30 mg dose applied to the scalp of six healthy men showed up in blood spots along with a breakdown product, which the authors called considerable exposure to the rest of the body; five metabolites were found in urine. It did not change the steroid profile used in athletes' biological passports. Because it blocks androgens and reaches the blood, tell your prescriber if you use it, especially with TRT or other hormone therapy.
We could not find a published human half-life or time to peak for RU-58841. The 2026 human study (six men, one 30 mg scalp dose) confirmed it reaches the blood but did not report a half-life, so we do not list one.
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