RU58841 for Hair Loss – Underused Finasteride Alternative?

Bonnke Arunga, MBBS

By    – Updated on March 9, 2023 – Reviewed by dermatologist Dr. Suneil Gandhi, MD

Ru58841 chemical formula

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Several medications are available for treating hair loss. Unfortunately, none of them are completely effective to restore your full head of hair. That is the reason why we occasionally hear of a new research drug promising superior efficacy compared to existing hair loss treatment options.

One such research drug is RU58841. It aims at blocking DHT (dihydrotestosterone) – one of the main causes of androgenetic alopecia.

What is RU58841?

RU58841 is a non-steroidal anti-androgenic medication that was initially developed in the 1980s as a topical treatment remedy for acne and male pattern baldness – androgenetic alopecia.

RU58841 goes by several names. It is also known as PSK3841 or HMR3841. It was renamed after newer companies bought the rights to the original product, RU58841.

How did RU58841 come about?

The concept of RU58841 is quite old. The idea to develop it was first put forth by a French pharmaceutical company called Roussel Uclaf, way back in the 1970s. Although it had been produced in the 80s, most of the research about its development progressed into the 90s.

The main aim of these scientists was to develop a potent medication that would effectively manage acne and androgenic alopecia when applied topically while avoiding/limiting systemic side effects that are commonly observed with other anti-androgens.

Rats and hamsters were the animal models used to test its effectiveness. During the trial phase of the mediation, the RU58841 results were very promising.

Actually, even small doses as low as 0.001 milligrams showed significant local effects. Even at high doses of up to 0.01 milligrams, the action was still limited to the site of application – a much-desired relief for the researchers.

A lot has transpired since the inception of the idea. For instance, several companies had acquired and dropped their right to this product. Eventually, one company – ProStraken – acquired the full rights to RU58841 and changed its name to PSK3841.

They conducted two human clinical trials (a phase 1 and a phase 2 trial). The phase 1 trial involved the application of 5% solution twice daily for 4 weeks, and the phase 2 trial compared the placebo to 2.5% and 5% solutions of RU58841 for 6 months. Although the results were apparently good and well tolerated, none of these were ever published.

Prostraken decided to conduct a phase 3 trial as well, but this never went ahead. The company was acquired by a Japanese company called Kyowa Kurin, after which the project got canceled for monetary reasons. 

Since then, similar studies on humans have not been conducted or published in peer-reviewed medical journals. A few monkey-based studies have been done, which determined the optimal dosing of RU58841 to be 5%, and one study compared it against finasteride.

The monkeys experienced an increase in hair growth of 103%, compared to just 88% for those given finasteride. The finasteride group had serum DHT levels lowered by 70%, while the RU58841 group had no change in levels.

Another study evaluated the effectiveness of RU58841 on human hair transplanted onto the skin of nude mice. However, as there have been no direct human studies for more than a decade, the FDA has not approved it for the management of any condition.

RU58841 mechanism of action

Since this medication is anti-androgen, it may be able to target androgen-dependent skin conditions such as acne and androgenic alopecia. Right now, you are probably aware that hair loss occurs due to the action of DHT on the hair follicles.

Other anti-androgenic drugs act by either reducing or blocking the synthesis of dihydrotestosterone (DHT). The mechanism of RU58841 is entirely different from other anti-androgenic medications. Here is the reason:

RU58841 competitively binds to the receptors of DHT. So, it actually blocks DHT from attaching itself to the receptors. It does not reduce the production of DHT. As a result, the systemic side effects that occur due to lowered production of DHT are not seen, for example, sexual side effects. 

Just like finasteride (but minus the side effects), the effects of RU58841 are as follows:

  • It inhibits the hair-thinning effects of DHT (dihydrotestosterone)
  • It increases the percentage of hair growth in the anagen phase
  • It improves hair density and diameter

How effective is RU58841?

The safety and effectiveness of RU58841 are quite impressive. The overall effect is really noticeable as can be seen in this RU58841 before and after comparison below.

r58841 hair regrowth before after
Self-claimed RU58841 patient (Source:

Evaluating the effectiveness of RU58841 will make us compare it to medications such as finasteride which inhibits or reduces the synthesis of DHT.

The mere fact that the effect of RU58841 does not interfere with the synthesis of DHT and testosterone, makes it a very promising drug. What is more, you don’t have to worry about side effects such as erectile dysfunction, which is relatively common with finasteride.

This is where RU58841 works differently. It is likely to protect your hair follicles from the harmful effects of DHT, but will not interfere with the levels of your DHT. All the benefits of DHT are left intact when you use RU58841.

However, one must take this with a pinch of salt – there are currently inadequate scientific studies that validate this claim. Many of the stories published online are claims from individuals who may either have a conflict of interest or are already on other hair-loss medications such as minoxidil and finasteride.

How to use RU58841?

The crucial part is knowing how to store this medication and how to use it. As previously mentioned, initial trials on this medication revealed that it is very potent even at low doses. A daily dose of 50 mg applied in areas that are affected by alopecia will usually suffice. 

It is available as a pre-made solution or raw powder. The pre-made solution comes in a concentration of 5% RU58841, at a dose of 50 mg/ml. The raw powder form is suited for those who want more control over the concentration, or want to mix it with minoxidil.

You should realize that RU58841 is not an FDA-approved medication thus you must stay cautious about the usage of this product. What’s more, it may be an economic disadvantage to overuse your medication.

Here is how to use it

man using dropper to apply hair loss solution

Using a dropper, apply 1 ml of the 5% solution on the areas that have suffered hair loss. Then, rub and spread it gently with your fingertips to ensure that it covers the target area evenly. After you have applied it, let it dry for about a minute.

The next procedure depends on whether you are using other hair treatments as well. For instance, this is the best time to apply your minoxidil if you are also using it to treat your hair loss.

When should you apply your RU58841?

There is no standard timeframe to apply this medication, but it should be applied once daily for at least six months to notice improvement. 

But one thing that you should put into account is that your skin always produces a lot of oil called sebum. This sebum reduces the penetrative value of RU58841. As a result, you may want to apply it about 20-30 minutes after taking a shower. Doing so will improve its penetrative value and overall effectiveness.

man washing his hair

RU58841 is a watery formulation. So you have to apply it carefully on the scalp, behind the hairline, and spread it to cover the target area. Be careful that it does not trickle down onto the forehead, sides of the face, and neck. Otherwise, the hairs in that region will also grow thicker over a period of time.

How to store RU58841?

It is important to store RU58841 in a dry, dark, and cool place – as it degrades in heat and sunlight. Pre-made solutions of RU58841 should be stored within a tightly closed bottle in a refrigerator. The raw powder should be stored within air-tight bags in a freezer.

Irrespective of how you store it, you should be careful not to expose it to high temperatures or sunlight, because these conditions will degrade the active compound and it may lose its effectiveness.

Side-effects of RU58841

Since RU58841 has not passed beyond phase two of drug development, there are no studies that have highlighted the side effects of this medication specifically.

This means that if there are any side effects, then they are actually unknown. For now, information about its side effects can only be derived online from the reviews of customers who have actually used the product. It has been found to be well tolerated by the people using it, and not many side effects have been reported. It may cause skin irritation or allergy. 

It is hoped that future studies will document the side effects of using RU58841. But based on the physiologic processes it undergoes, we can hypothesize on some of its potential side effects.

For instance, you should be aware that RU58841 not only blocks DHT but all other androgens including testosterone. So if this enters your bloodstream, it can lead to side effects such as fatigue, headache, dizziness, decreased libido, erectile dysfunction, chest pain, etc.

This is the reason why it is advisable that you use RU58841 with caution. Do not apply it on raw skin. If possible, consult your doctor or healthcare provider before you use this product, or when you notice symptoms after using it.

Where to buy RU58841?

Most of the purchases for RU58841 can be made online from several of the most popular suppliers like Chemyo, Kane, and Anagen Inc. Recommendations are that it can only be purchased for the purpose of research or experiments.

As a result, you should actively think through it and decide if it is indeed the medication you want. Once you have made up your mind, choose the 99% pure grade while taking care to read the label carefully so that nothing is appearing out of place.

Another factor you should be aware of is that the medication is not regulated by the FDA. As a result, there are no guarantees that you will get what you see advertised.

Alternatively, you can purchase the pre-made version from Chemyo. Though like any other RU58841 product, it is not FDA regulated.

bottle of RU58841

RU58841 5%, 50ml

  • 5% RU58841 concentration
  • Other ingredients: 70% ethanol, 25% propylene glycol
  • Third-party (laboratory) tested


RU58841 is one of the few experimental products that may actually help you to manage androgenetic alopecia. However, the fact remains that it is not recognized or regulated by the FDA. This makes vendors mess around with the concentration and purity of the product.

One of the options is to make formulations yourself, but this process is quite complicated. You may not even get a genuine product to begin with. Moreover, RU58841 can cause unwanted side effects if it gets into your bloodstream, so it has to be used with caution.

Thus consult your doctor and consider other tried and tested options for hair loss, like minoxidil, oral or topical finasteride (the more widely used RU58841 alternative), or laser light devices, before considering this one.

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