Category Archives: RU-58841

The Strange Predicament of RU58841

RU-58841 MezogenRX. 2% Formulation.

In the early 1990s, scientists in France synthesized a new topical anti-androgen called RU58841 (or RU-58841). This product was effective at tackling various androgen related disorders, including hair loss, acne and hirsutism.

Since that time, a few favorable studies have been published that have shown the effectiveness of RU58841 in regrowing hair (in hamsters, humans and mice) at low doses.

In some countries, you can purchase products that contain RU-58841 as an ingredient. The MezogenRX product on the right is from Indonesia and it contains 2% RU-58841 in addition to Minoxidil Sulphate.

RU58841 Antiandrogen for Hair Loss

In the US, you can even buy RU-58841 from Amazon via brands such as Vantanex (in a 5% solution).

However, unlike Minoxidil or Finasteride, the US FDA has not approved the use of RU58841 for treating scalp hair loss. The product cannot be prescribed at pharmacies and is not meant to even be used by humans. RU58841 is classified as a chemical and can be purchased by pharmacists in the US for independent research. Strangely enough, it is sometimes sold on Amazon in various powder and spray versions.

RU58841 Powder.
RU58841 Powder.

It does not seem like the chemical has been approved anywhere in the world to treat hair loss and balding. This has not prevented numerous hair loss sufferers around the world from getting their hands on RU58841 and using it.

Although illegal, this is not surprising to a hair loss sufferer such as myself. People on hair loss forums have tried much crazier things in the past, and will always do so. Internet commerce also makes law enforcement that much harder. The below video is an interesting take on one brand of RU.

Hair Growth Results

You can find dozens of very positive online testimonials regarding RU58841 from reputable and active members on hair loss forums. It should be noted that some of these testimonials may credit RU58841 for positive results, when in fact the person is also using Minoxidil and/or Finasteride and/or Dutasteride. Therefore making it hard to gauge which product is most responsible for the positive results.

Among the more interesting RU58841 related testimonials from active forum members or youtubers include those from: Mr. Antiandrogen1; hellouser; and Swooping. You can also find before and after photos with testimonials on Reddit. Almost all are from men suffering from male pattern baldness and thinning hair. Women rarely seem to take this strong antiandrogen.

RU58841 Side Effects

Topical RU58841 has a very short half-life (1 hr) in comparison to the oral ingestion of Finasteride (6 hrs) and Dutasteride (5 weeks!). Moreover, RU58841 does not inhibit dihydrotestosterone (DHT) production like the latter two hair loss treatment products. These facts seem to suggest that there is minimal chance of any serious or permanent side effects. Anecdotal evidence on the forums seems to support this conclusion. Carcinogenic effects such as cancer are not proven.

However, because many people are buying RU58841 from online sometimes unknown and unverified suppliers, there is no guarantee of any kind of safety. I am not planning to buy RU58841 online because of safety issues. The product is also quite expensive in comparison to Minoxidil or Finasteride. If you really do wish to buy this product, consult a doctor first.


Coming back to the title of this blog post, why do I find RU58841’s predicament strange? The answer is due to the fact that despite a respectable amount of evidence over the past two decades in support of the product’s anti-androgenic capabilities, no company has decided to go through with clinical trials for this product for use as an anti-androgen. This is especially surprising considering that side effects are likely to be minimal to non-existent when RU58841 is taken in low doses.

Perhaps companies do not think that the product is much better than topical Minoxidil? Or because the product cannot be patented, the long-term profitability and monopoly of any new product containing RU58841 is suspect? Even stranger, the research on this product has dried up in recent years. This situation is not true for other well known anti-androgens such as Spironolactone and Flutamide.

History of RU58841

It seems like the original RU58841 was renamed to HMR3841, and then to PSK3841 after a company named ProStrakan acquired rights to it. I assume that the current name is yet again RU58841?! Thanks to commentator “yo” for pointing out that this fact was mentioned in hellouser’s lengthy forum thread that I linked to earlier in this post. More importantly, PSK3841 was analyzed in a 2005 Morgan Stanley report and I am pasting the favorable analysis below:

“ProStrakan’s topical androgen receptor antagonist has completed a Phase IIa proof-of-concept study for alopecia. In this trial, which was not powered for efficacy, there was an observed increase in both new and existing hair growth and the data compared well with historical data for finasteride (marked by Merck as Propecia). We believe the market for this agent is resonably modest – US $100 – 200 million – but that could be of interest to a specialty dermatology company.”

Also, I found details about a human study on PSK3841 that was supposedly done in 2002, but am not sure if it was ever completed. If anyone lives in France, please see if you can contact Dr. Evelyne Guénolé, the primary contact person for that study.