N=1 After 40

Successful experiment · Started August 28, 2026 · Closed October 2, 2026

RU58841

Topical RU58841 stopped a period of drastic hair shedding. I did not see regrowth, thicker hair, or stronger hair during the run. I am closing it as successful for shedding control so I can test another hair compound, and RU58841 stays my fallback if nothing better covers both protection and growth. Personal experiment record, not medical advice, prescribing, sourcing guidance, or an instruction to copy.

Outcome: Successful for shedding. The heavy shedding stopped; hair count, thickness, and strength showed no visible change.

The Experiment

The question

Could a topical androgen-receptor blocker stop visible shedding or improve hair retention while testosterone and nandrolone stayed in my routine?

What I did

From August 28 to October 2, 2026, I sprayed RU58841 across the whole scalp twice a day: once in the morning and once before sleep. I focused on full coverage rather than a measured amount per application.

Result: shedding

Shedding had been drastic before I started. RU58841 essentially stopped it. That was the main reason for the experiment, and it worked.

Result: regrowth and hair quality

I saw no sign that it rolled back loss, increased the amount of hair, or made existing hair stronger. In this run RU58841 worked as protection, not as a growth treatment.

Decision: successful, closed

Continuing would make sense on the shedding result alone. I am closing it on October 2, 2026 because I want to test another compound, ideally one that both protects and improves hair: more hair, stronger hair. If I do not find something better on both fronts, I expect to return to RU58841.

Research Summary

What it is

RU58841 is an investigational nonsteroidal androgen-receptor antagonist developed by Roussel-Uclaf for acne and androgenetic alopecia. Instead of lowering DHT production, it competes for the androgen receptor in the follicle, so it targets the signal from whichever androgen arrives.

Why it fit my hormone context

Finasteride and dutasteride inhibit 5-alpha-reductase. That enzyme turns testosterone into the stronger DHT, but it turns nandrolone into the weaker dihydronandrolone. Blocking it alongside nandrolone can therefore push the two pathways in opposite directions. RU58841 leaves that conversion alone and acts at the receptor.

Published evidence

The hair evidence is preclinical. Topical RU58841 increased hair density, thickness, and length in stump-tailed macaques. In balding human scalp grafts kept on nude mice, 8 of 29 treated follicles entered a new growth cycle compared with 2 of 28 controls. Two registered human studies, a four-week safety study and a six-month efficacy study, never published results.

Topical is not scalp-only

The original case for local action came from hamster work, where 1 µg applied to the skin matched the effect of 300 µg injected. A 2026 human study found that a single 30 mg scalp application produced considerable systemic exposure, with metabolites detectable in urine for up to 213 hours, while the measured steroid profile did not change after that one dose.

The effect depends on continued use

As a competitive antagonist, RU58841 works only while it occupies the receptor. In hamster sebaceous glands, the effect peaked by four weeks and was gone within four weeks of stopping. If shedding returns after this closure, that matches how the compound works.

Sources