Finasteride vs RU58841

The Dose Guy’s verdict

Oct 27, 2026
8 sources

Finasteride, and it is not close. Finasteride has decades of human trials; RU58841 has macaques, rats, and scalp grafts on mice, and zero human trials. RU58841’s pitch is blocking DHT at the scalp without touching your hormones, and topical finasteride already does a version of that with a phase 3 trial behind it. If you run RU58841 anyway, run it on top of finasteride and minoxidil, never instead of them. If you want a topical antiandrogen to watch, pyrilutamide is the better bet.

Which would I take?Finasteride, topical if you can.

How they differ

Both go after DHT, the hormone shrinking your follicles, from opposite ends. Finasteride stops your body making it: it blocks the enzyme that converts testosterone, so DHT falls in your scalp and in your blood. RU58841 leaves DHT alone and tries to block the androgen receptor, the lock DHT turns, right at the follicle. On paper that is the cleaner trick, with no change to your hormone levels and so no sexual side effects. The paper is the problem. Nobody has measured how much RU58841 gets from your scalp into your blood, and long-term users reporting lower libido and the odd case of gynecomastia suggest some of it does.

The practical gap is supply and proof. Finasteride is a pharmacy drug with a known dose in every tablet. RU58841 is a research chemical: powder you dissolve yourself, a COA you hope is honest, and a compound that breaks down in water and lives in the fridge. If fear of finasteride’s sexual side effects is what sent you here, topical finasteride is the tested answer. Pyrilutamide chases RU58841’s mechanism through actual clinical trials, which is why it is the one I would watch.

What the research shows

One side has human trials and the other has none, so this is not a contest of numbers:

No clinical trial has tested RU58841 in living people, so none has compared it with finasteride.as of Aug 2026

Among men who stayed on blinded treatment, finasteride 1 mg daily produced 138 more hairs than placebo in a 5.1 cm² balding vertex area at year 2.JAAD 1998 · phase 3 · n=1553

Topical finasteride increased hair count by 20.2 hairs versus 6.7 with placebo at 24 weeks, numerically similar to oral, with peak plasma concentration more than 100 times lower. Serum DHT still fell 34.5%, against 55.6% on oral.JEADV 2022 · phase 3 · n=458

Topical RU58841 increased hair density, thickness, and length in a macaque model of androgenetic alopecia, with no detectable systemic effects.Endocrine 1998 · macaque

With the androgen receptor and its coactivator ARA70 cotransfected at a 1 to 3 ratio into DU145 cells, RU58841 significantly enhanced androgen receptor transcriptional activity.PNAS 1998 · in vitro · cotransfection

The finasteride numbers are men. The RU58841 numbers are a monkey and a dish, and the dish disagrees with the pitch.

How people run them

The foundation is finasteride, 1 mg a day by mouth or topical finasteride daily, which is where I would start most people, paired with minoxidil. Give it six months before judging and a full year before changing anything.

People on Reddit run RU58841 three ways: instead of finasteride out of side-effect fear, after finasteride gave them side effects, or on top of finasteride chasing more. The first is the one I would talk you out of: you trade a drug with human data for one without, to dodge a risk topical finasteride already cuts. If oral finasteride gave you side effects, try topical finasteride before RU58841. If finasteride was not enough, the next tested step is dutasteride.

If you run RU58841 anyway, run the community standard, not more: 5% in an anhydrous ethanol and propylene glycol vehicle, once a day, usually at night, mixed in small batches and kept cold. Keep it on top of the proven stack so your hairline never rides on it alone. Add it on its own, not in the same week as any other change, take monthly photos, and stop if palpitations, chest tightness, mood changes, or breast tenderness show. Whatever it holds goes when you stop, same as finasteride.

Finasteride, topicaldailySame scalp benefit, far less in your blood. The better start for most.

Finasteride, oral1 mg/dayOne pill, any time of day.

The stack+ minoxidilThe proven pair, and the floor under anything else.

Sides on oraltopical finasterideThe tested fix, before reaching for an untested one.

Not enoughdutasterideThe next step up with human trials behind it.

RU588415%, once dailyCommunity standard, not human dose-finding. An add-on, never the base.

Side effects, side by side

Finasteride’s side effects are measured; RU58841’s come from forums:

commonLower libido, softer erections, or less ejaculate on finasteride, in a small minority. Most resolve after stopping, and topical lowers the exposure.

anecdotalScalp irritation and flaking on RU58841, usually from the vehicle. Switching vehicles often fixes it.

anecdotalLower libido, mood changes, and rare gynecomastia from long-term RU58841 users. Those are the systemic antiandrogen signals it was supposed to avoid.

anecdotalPalpitations and chest tightness on RU58841 in a small minority. Stop and reassess.

monitorKeep both away from a partner who is or could be pregnant. Finasteride can harm a developing male fetus, and an antiandrogen on your pillowcase is the same worry with no data.

unknownRU58841 has no human safety data at any timepoint. Absorption, metabolism, and long-term effects in people are all unmeasured.