RU58841 vs Finasteride: Which Works Better? The Numbers, Side by Side

I took finasteride myself. About six to eight weeks in, the side effects hit. Lower libido, brain fog, a general feeling of being "off". I came off it.

I'd already had a hair transplant at 27. I needed a way to protect it that didn't mean messing with my hormones. That's when I found RU58841. I've used it every day for over four years, and it's why I started RUrestore.

This is RU58841 vs finasteride, honestly. How each one works, what the side effects look like, what the studies say, and which one makes sense for you. Every study is linked so you can check it.

But first, the one I always talk about. When they were put head to head, RU58841 beat finasteride.

How finasteride works: lowering DHT across your whole body

Finasteride is a pill. It blocks an enzyme called 5 alpha reductase, which turns testosterone into DHT. DHT is the hormone that shrinks hair follicles in men with pattern hair loss.

The standard 1mg dose cuts the DHT in your blood by about 71% (Drake 1999). That's not just at the scalp. That's everywhere. It doesn't aim for the hair follicle. It lowers DHT across the board.

That's why it works. It's also why some men get side effects.

What finasteride does well

Credit where it's due. Finasteride has decades of research behind it. In two big trials, 1,553 men took it for up to two years. It slowed hair loss and grew hair, while the men on the dummy pill kept losing hair (Kaufman 1998). It's approved, it's prescribed everywhere and it's cheap. If you take it and feel fine, it can work for years.

How RU58841 works: blocking DHT at the follicle

RU58841 does it differently. It goes on your scalp. It sits on the receptor in the follicle that DHT plugs into, so DHT can't bind.

Finasteride stops your body making DHT. RU58841 lets your body make DHT as normal, then stops it attaching to the receptors in your scalp.

Finasteride is a bomb going off in your body, getting rid of DHT everywhere. RU is a sniper rifle. It hits where you want it and leaves the rest.

In the animal studies it didn't change testosterone or DHT in the blood (Battmann 1994, Ye 1997). Some of it does reach the blood. A 2026 study found it in the blood of six men after one dose on the scalp, and their steroid hormone profile didn't change (Okutan 2026). RU works at the scalp. It doesn't lower your DHT.

RU58841 was made by the French drug company Roussel Uclaf. The first paper on it came out in 1994. It never made it to market. More on that below.

Want the full background? Read What Is RU58841?

Side effects: RU58841 vs finasteride

This is where it gets real. For a lot of men the question isn't which one works better on paper. It's which one they can live with.

Finasteride side effects

The ones men report most:

• Lower libido.
• Erection problems. A review of 12 trials found finasteride raised the risk. Roughly one extra man in every 82 treated (Mella 2010).
• Brain fog and low mood. Depression is now listed on the finasteride label (Irwig 2012).
• Less ejaculate.

Then there's post finasteride syndrome, where side effects carry on after you stop. Doctors argue about it. But there are published cases: 71 men whose sexual side effects lasted an average of 40 months after stopping (Irwig 2011). It's a small, self selected group, so it doesn't tell you how common it is. Wherever you land on it, the sexual side effects while you're on the drug are established.

RU58841 side effects

What people report:

• Dry or itchy scalp. The most common one. Usually the alcohol in the liquid rather than the RU itself.
• A shed at the start. Common in the first 6 to 8 weeks. Weak hairs make way for stronger ones.
• A racing heart. A small number of users report it. There's no study confirming a link.
• Lower libido. Some users say theirs dipped. I've had none of it in four years.

What we know comes from animal studies, human scalp grafted onto mice, a monkey study where it beat finasteride, and a lot of men using it for years. Not approved doesn't mean it doesn't work. Full detail: RU58841 Side Effects.

How well does each one work?

Before the head to head, here's everything men weigh up when they want to keep their hair. Here are the real numbers from the studies, each one linked so you can check it. Every study measured things a bit differently, so read each line on its own.

• RU58841 on the scalp: strong. In bald monkeys, RU58841 5% raised growing follicles by 103% and turned 26% of thin hairs into thick ones. The finasteride pill got 88% and 12% in the same study, and RU did it with no hormone change. On real balding human scalp grown on mice, 28% of follicles started a new growth cycle with RU, against 7% without it. (Uno monkey study, not on PubMed; same team: Pan 1998, De Brouwer 1997)
• Finasteride pill: strong. 1,553 men. After two years, men on finasteride had 138 more hairs in a one inch circle on the crown than men on a dummy pill, who kept losing hair. It cuts the DHT in your blood by about 71%, which is why some men get side effects. (Kaufman 1998, Drake 1999)
• Topical finasteride: good. 458 men, 24 weeks. Hair count up 20.2 hairs, against 6.7 on a dummy spray. About the same as the pill. Blood DHT still dropped 34.5% (the pill: 55.6%). (Piraccini 2022)
• Dutasteride pill: the strongest pill. 917 men, 24 weeks. Dutasteride 0.5mg grew more hair than finasteride 1mg. It also cuts blood DHT by about 95%, so it hits your hormones harder. (Gubelin Harcha 2014, Clark 2004)
• Minoxidil 5%: good. 393 men, 48 weeks. 5% beat the dummy and grew 45% more hair than 2%. It doesn't touch DHT, so it works best next to a DHT blocker. (Olsen 2002)
• Dermastamp (microneedling): a big boost. 100 men, 12 weeks. Weekly microneedling plus minoxidil: hair count up 91.4. Minoxidil alone: up 22.2. 82% said their hair was more than 50% better, against 4.5% on minoxidil alone. (Dhurat 2013)

Short version: stop the DHT first, then grow the hair. That's a DHT blocker plus minoxidil, with a dermastamp once a week. RUstim+ does the first two in one bottle.

RU58841 vs finasteride: head to head

RU58841 vs finasteride at a glance

	Finasteride	RU58841
How you take it	Pill, once a day	On the scalp, once a day
How it works	Stops your body making DHT	Blocks DHT at the follicle
DHT in your blood	Down about 71%	Not lowered in the studies
Approved?	Yes, on prescription	No
Research	Big human trials over decades	Animal studies and human scalp on mice
Sexual side effects	Documented in trials	Some users report lower libido, no trial data
Best for	Men who take it and feel fine	Men who want to block DHT without a pill

Does RU58841 actually work?

Based on the evidence there is, yes. Here's what it is.

• Head to head with finasteride, in monkeys. RU58841 5% on the scalp got growing follicles up 103% against 88% for finasteride, and turned 26% of thin hairs thick against 12%, with no hormone change. The full table is at the top of this article.
• Human balding scalp, grown on mice. 28% of follicles restarted growth on RU58841, against 7% on plain alcohol. Hair grew faster too (De Brouwer 1997).
• Bald macaques. Monkeys that go bald like men grew denser, thicker, longer hair, with no effects on the rest of the body detected (Pan 1998, Obana 1997).
• Next to finasteride on skin. On rat skin, RU58841 shrank hormone driven oil glands as much as castration did, and more than finasteride. Blood testosterone and DHT didn't change, and only finasteride shrank the prostate (Ye 1997). That was a skin study, not a hair study.

Finasteride has stronger human evidence. That's a fact. But "more researched" doesn't automatically mean "works better". It means more money was spent proving it, because there was money to be made.

Why isn't RU58841 approved?

Everyone asks this. If it works, why can't you get it on prescription?

The honest answer: nobody outside the companies involved knows for sure. The company that made it went through mergers in the late 1990s, and development quietly stopped. No official reason was ever published.

Here's what we do know. Nobody owns it now. Nobody's going to spend hundreds of millions taking a drug through approval when anyone can make it.

Not approved doesn't mean it doesn't work.

What about topical finasteride and dutasteride?

• Topical finasteride goes on your scalp instead of down your throat. In a trial of 458 men it grew about as much hair as the pill, but still lowered blood DHT by about 35% (Piraccini 2022). Less than the pill. Not zero.
• Dutasteride is finasteride's stronger brother. It cut blood DHT by about 95% (Clark 2004) and grew more hair than finasteride in 917 men (Gubelin Harcha 2014). If lowering DHT everywhere is what you're trying to avoid, it's the wrong direction.
• Minoxidil doesn't touch DHT at all. It makes hair grow. It's a partner for either of them, not a replacement.

Every option ranked: How to Stop Hair Loss Without Finasteride.

Who should choose finasteride?

Finasteride might be right for you if:

• You want an approved treatment with big trials behind it.
• You've taken it before with no side effects.
• You'd rather swallow a pill than put something on your scalp.
• Your doctor recommends it for you.

Finasteride works for a lot of men without problems. If you're one of them, there's no reason to switch out of fear.

Who should choose RU58841?

RU58841 makes more sense if:

• Finasteride gave you side effects.
• You don't want to lower your DHT across your whole body.
• You've had a transplant and want to protect it.
• You're happy with animal studies and real world use rather than big human trials.

That's the path I chose. After finasteride's side effects and a transplant, I needed something to protect my hair without the trade off. RU58841 did it.

Can you use RU58841 and finasteride together?

Some men do. A low dose of finasteride for the whole body, RU58841 on top at the scalp. Two angles.

If you try it, start one thing at a time. Start both at once and you'll never know which one's causing what. If finasteride gives you problems, RU58841 on its own may be enough. Talk it through with your doctor.

Frequently asked questions

Is RU58841 safer than finasteride?

It's a different kind of risk. RU58841 goes on your scalp and, in the studies, didn't lower blood DHT. Finasteride lowers DHT across your body and has documented sexual side effects. But finasteride has far more human research. Which is "safer" depends on how you weigh those two things.

Does RU58841 work as well as finasteride?

In monkeys, it did better. RU58841 5% on the scalp beat finasteride head to head on growing follicles and thick hairs, and didn't change their hormones. Both go after DHT, in different ways. Finasteride lowers it everywhere. RU blocks it at the scalp.

Can I switch from finasteride to RU58841?

Plenty of men do, especially after side effects. A lot of them start RU58841 a few weeks before they stop finasteride, so the follicle's never left unprotected. Speak to the doctor who prescribed it before you stop.

How long does RU58841 take to show results?

Expect a shed in the first 6 to 8 weeks, new growth from months 2 to 3, and proper density by month 6. Use it every day. Full timeline: How Long Does RU58841 Take to Work?

Where can I buy RU58841 I can trust?

Only from someone who shows you an independent lab test. Raw powder from unknown sellers can be anything. Our RU58841 has been lab tested by Janoshik. More here: Where to Buy RU58841 in the UK.

The bottom line

Both go after DHT. The difference is how and where.

Finasteride is the established option. Approved, well researched, and works for men who handle it. But it lowers DHT across your whole body, and some men pay for that.

RU58841 is the targeted option. It goes on your scalp and blocks DHT where your hair is. What it has is early research that points the right way, a monkey study where it beat finasteride, and a lot of men using it for years.

I chose RU58841 because I'd lived with finasteride's side effects and wasn't willing to keep paying that price for my hair.

Sources

1. Uno and colleagues. Conference abstract, Wisconsin Regional Primate Research Center. Follicular regrowth with 5α reductase inhibitor (finasteride) or androgen receptor blocker (RU58841) in the bald scalp of the stumptailed macaque. RU58841 5% on the scalp beat oral finasteride on growing follicles (up 103% vs 88%) and thin to thick hairs (26% vs 12%), with no hormone change. Not on PubMed. Published RU58841 work in the same monkeys: Pan 1998, Endocrine.
2. Drake and colleagues (1999). J Am Acad Dermatol. Finasteride 1mg cut blood DHT by about 71% and scalp DHT by about 64%. PubMed 10495374
3. Kaufman and colleagues (1998). J Am Acad Dermatol. 1,553 men: finasteride slowed hair loss and grew hair over two years. PubMed 9777765
4. Mella and colleagues (2010). Arch Dermatol. Review of 12 trials: more hair, higher risk of erection problems. PubMed 20956649
5. Irwig and Kolukula (2011). J Sex Med. 71 men with sexual side effects that lasted after stopping finasteride. PubMed 21418145
6. Irwig (2012). J Clin Psychiatry. Low mood in former finasteride users with lasting sexual side effects. PubMed 22939118
7. Battmann and colleagues (1994). J Steroid Biochem Mol Biol. RU58841 worked where applied, no effect on testosterone level. PubMed 8136306
8. Ye and colleagues (1997). Skin Pharmacol. RU58841 and finasteride on rat skin. PubMed 9449168
9. Okutan and colleagues (2026). Biomed Chromatogr. RU58841 found in the blood of six men after one scalp dose, steroid profile unchanged. PubMed 42615108
10. De Brouwer and colleagues (1997). Br J Dermatol. Human balding scalp on mice. PubMed 9415227
11. Obana and colleagues (1997). Endocrinology. Hair regrowth on bald macaque scalps. PubMed 8977424
12. Pan and colleagues (1998). Endocrine. More hair density, thickness and length in bald macaques. PubMed 9798729
13. Piraccini and colleagues (2022). J Eur Acad Dermatol Venereol. Topical finasteride in 458 men. PubMed 34634163
14. Clark and colleagues (2004). J Clin Endocrinol Metab. Dutasteride and blood DHT. PubMed 15126539
15. Gubelin Harcha and colleagues (2014). J Am Acad Dermatol. Dutasteride against finasteride in 917 men. PubMed 24411083
16. Olsen and colleagues (2002). J Am Acad Dermatol. 5% minoxidil grew 45% more hair than 2%. PubMed 12196747
17. Dhurat and colleagues (2013). Int J Trichology. Weekly microneedling plus minoxidil against minoxidil alone, 100 men. PubMed 23960389

I'm not a doctor and this isn't medical advice. Don't stop a prescribed medicine without talking to your doctor.