RU-58841 (PSK-3841)

How RU-58841 (PSK-3841) Works, Results, Usage, and Side Effects

For those grappling with androgenetic alopecia (AGA), or male pattern baldness, the search for a therapeutic elixir is ongoing. Amidst an array of treatments, RU-58841 emerges as a standout, touted for its efficacy in both halting hair loss and promoting regrowth. This article delves deep into the mechanism behind RU-58841’s therapeutic effects and the research studies buttressing its potential.

Close up showing before and after results of using RU-58841 to treat hair loss and balding

What is RU-58841?

RU-58841, also known as PSK-3841 or HMR-3841, is a synthetic non-steroidal antiandrogen that treats hair loss, particularly androgenetic alopecia (male pattern baldness). It works by binding to androgen receptors in the scalp, blocking the effects of dihydrotestosterone (DHT), a hormone linked to hair follicle miniaturization and hair loss in genetically predisposed individuals. By inhibiting DHT’s impact on the hair follicles, RU-58841 aims to slow down or potentially reverse hair loss. It has garnered attention as an alternative to other anti-androgen treatments like finasteride, which can have systemic side effects.

History of RU-58841

RU-58841, a nonsteroidal antiandrogen, was first developed as a potential remedy for androgen-related conditions, including benign prostatic hyperplasia (enlarged prostate) and androgenetic alopecia (male pattern baldness).

Initially, the compound emerged from the research efforts at Roussel-Uclaf, a French pharmaceutical company, in the late 1980s. The company’s researchers were focusing on a series of compounds that targeted androgen receptors in the body. Specifically, RU-58841 was crafted to act as a topical antiandrogen. This meant it could be directly applied to the scalp as a lotion or cream, aiming to treat male pattern baldness without the systemic side effects common with other antiandrogenic medications.

Subsequently, early studies of RU-58841 in animal models showed promising results. It appeared effective in reducing androgen-related impacts on hair follicles, thereby encouraging hair regrowth. Consequently, this sparked significant interest in RU-58841 as a viable treatment option for androgenetic alopecia.

The Role of DHT in Androgenetic Alopecia

Dihydrotestosterone (DHT) is a hormone derived from testosterone, and it plays a significant role in hair loss, particularly in androgenetic alopecia (male and female pattern baldness). In individuals with a genetic predisposition to hair loss, hair follicles in certain areas of the scalp are sensitive to DHT. When DHT binds to receptors in these follicles, it can lead to a process known as miniaturization. This process causes the hair follicles to shrink over time, resulting in thinner and shorter hair growth cycles. Eventually, the affected follicles may stop producing hair altogether, leading to baldness in those areas. Therefore, DHT is a key factor in the development and progression of hair loss, and treatments often target its effects to mitigate or reverse the condition.

How RU-58841 Treats Hair Loss

RU-58841 prevents hair loss by topically blocking the hormone dihydrotestosterone (DHT) from binding to androgen receptors in hair follicles. By preventing DHT from exerting its harmful effects on follicles, RU-58841 helps maintain their size and function, potentially promoting thicker and healthier hair growth in individuals susceptible to androgenetic alopecia.

The main mechanisms of action are:

    • Competitive Inhibition: Central to RU-58841’s therapeutic arsenal is its ability to prevent DHT from binding to ARs. It achieves this by acting as a competitive inhibitor, thereby reducing DHT’s impact on the hair follicles. By thwarting the binding of DHT to its receptors, RU-58841 ensures that the downstream signaling events, which culminate in follicular miniaturization, are halted.
    • Receptor Specificity: Molecular affinity is of paramount importance. RU-58841 is tailored to show a high affinity for scalp follicular androgen receptors. This ensures that the drug’s action is concentrated in the area of application, bolstering its efficacy and minimizing systemic absorption or impact.
    • Limited Systemic Absorption: One of RU-58841’s most notable attributes is its limited systemic absorption. When topically applied, the vast majority of the compound remains localized, thereby vastly reducing potential systemic side effects. This localized action is paramount for an anti-androgen, as it limits the possibility of unwanted systemic hormonal disturbances.

Empirical Evidence

The empirical evidence surrounding RU-58841’s potential for treating hair loss has been a subject of interest and scrutiny. This evidence encompasses a range of studies, including in vitro validation, animal model efficacy tests, and preliminary human clinical trials, all aimed at shedding light on the compound’s effectiveness in addressing the complex issue of hair loss.

  • In Vitro Validation:
    • Battmann et al. (1994) conducted a study using human foreskin samples. Through binding assays, the researchers demonstrated that RU-58841 robustly inhibited DHT and testosterone from latching onto ARs. This evidence marked the foundational understanding of the drug’s potential efficacy in a human context.
  • Animal Model Efficacy:
    • Stump-tailed macaques were used as models in a study by Probst et al. (1997). These primates exhibit male pattern baldness similar to humans. When topically administered RU-58841, there was a significant surge in hair density, thereby confirming the compound’s in vivo efficacy. This study cemented RU-58841’s potential as a translatable treatment for human AGA.
  • Human Clinical Trials:
    • The transition from bench to bedside is pivotal. Preliminary human trials involving RU-58841 have underscored its promise. However, it’s crucial to note that large-scale clinical trials, which would provide a holistic understanding of its efficacy and safety profile, are still in their early stages.
Close up showing before and after clinical trial results of using RU-58841 for treating hair loss

Researchers tested RU-58841 on macaques (monkeys) and noted that the 5% topical group showed an impressive 103% increase.


Anecdotal reports from some individuals who have used RU-58841 suggest varying degrees of success in addressing hair loss. These reported results should be taken as anecdotal and not as conclusive evidence of the compound’s effectiveness or safety. Here are some of the successful results that have been reported:

  • Slowed Hair Loss: Users have reported that RU-58841 helped slow down the progression of hair loss. They observed that they were shedding fewer hairs and that their hairline or thinning areas stabilized.
  • Improved Hair Thickness: Users claim that RU-58841 contributed to increased hair thickness and diameter, making their existing hair appear fuller and healthier.
  • Hair Regrowth: While not common, some individuals reported experiencing new hair growth in previously bald or thinning areas after using RU-58841. These users noted the emergence of new hair strands in areas where they had previously lost hair.
  • Minimal Side Effects: Many users reported experiencing minimal or tolerable side effects, such as mild scalp itching or redness. This was seen as a positive aspect of RU-58841 use.
Close up showing before and after results of using RU-58841 to treat hair loss and balding

Before and after results of using RU-58841 to treat hair loss. 

How to Use RU-58841

The application of RU-58841 for hair loss typically involves topical use, as it is intended to be applied directly to the scalp. Here are general guidelines for applying:

  • Clean Scalp: Start with a clean and dry scalp. You can wash your hair with a mild shampoo and ensure that the scalp is free from excess oil, dirt, and debris.
  • Measure the Dose: Follow the dosing instructions provided by the manufacturer or supplier. Typically, a small amount of RU-58841 solution is applied to the scalp.
  • Apply to Affected Areas: Use a dropper or applicator to apply the RU-58841 solution directly to the areas of the scalp where you are experiencing hair loss or thinning. It’s important to target the areas where the hair follicles are sensitive to DHT.
  • Massage Gently: After applying the solution, use your fingertips to gently massage it into the scalp. This helps distribute the product evenly and stimulates blood flow to the follicles.
  • Allow to Dry: Allow the RU-58841 solution to dry naturally. Avoid using a hair dryer or heat source to speed up the drying process, as this may reduce effectiveness.
  • Frequency of Use: The frequency of application can vary depending on the product and individual preferences. Some users apply RU-58841 once a day, while others apply it less frequently. Follow the recommended dosing instructions, and consult with a healthcare professional if you are unsure about the appropriate frequency for your specific needs.
  • Be Consistent: Consistency in application is essential for potential effectiveness. It may take several months of regular use to see any noticeable results, and individual responses can vary.
  • Monitor for Side Effects: Keep an eye out for any adverse reactions, such as skin irritation, redness, or itching. If you experience any significant or persistent side effects, discontinue use and consult a healthcare professional.


Proper storage of RU-58841 is essential to maintain its stability and effectiveness. While specific storage instructions may vary depending on the manufacturer or supplier, here are some general guidelines for storing RU-58841:

  • Temperature: RU-58841 is typically best stored at a controlled room temperature, typically around 20-25°C (68-77°F). Avoid exposure to extreme heat or cold, as temperature fluctuations can affect the stability of the compound.
  • Light: Keep RU-58841 away from direct sunlight and strong ultraviolet (UV) light, as light exposure can degrade certain chemical compounds. Store it in a dark or opaque container.
  • Moisture: Prevent moisture or humidity from coming into contact with RU-58841. Store it in a dry environment to avoid degradation.
  • Sealed Container: Ensure that the container or bottle of RU-58841 is tightly sealed when not in use to prevent air exposure, which can affect its stability.
  • Keep Out of Reach of Children: Store RU-58841 in a safe and secure location, away from the reach of children and pets.
  • Follow Manufacturer’s Instructions: Always follow any specific storage instructions provided by the manufacturer or supplier. Different products may have unique storage requirements.

Safety and Side Effects

RU-58841 is generally considered safe when applied topically to the scalp, and, unlike oral medications, it is less likely to cause systemic side effects. Here are some important considerations to be aware of when deciding if RU-58841 is right for you:

  • Limited Safety Data: The lack of comprehensive clinical trials means that there is a scarcity of controlled, systematic safety data for RU-58841 in humans. This makes it difficult to determine the full extent of potential side effects and long-term safety.
  • Potential Side Effects: Some users have reported side effects associated with RU-58841 use, including skin irritation, scalp itching, redness, and dryness at the application site. These side effects are typical of many topical solutions and may vary among individuals.
  • Systemic Effects: RU-58841 is designed for topical use to minimize systemic absorption. However, there may be concerns about the compound’s potential to enter the bloodstream, especially if applied excessively or on damaged skin. Systemic absorption could potentially lead to hormonal imbalances or other adverse effects.
  • Unknown Long-Term Effects: Because of the limited duration of use reported by most users and the absence of long-term studies, the safety of prolonged or continuous use of RU-58841 remains uncertain.
  • Regulatory Status: RU-58841 had not received regulatory approval in many countries for the treatment of hair loss. This means it had not been subject to the same safety and efficacy evaluations required for FDA-approved treatments.

Given these uncertainties, individuals considering the use of RU-58841 should exercise caution and consult with healthcare professionals before use. It is essential to discuss potential risks, benefits, and alternatives with a medical expert.


In the multifaceted realm of AGA therapeutics, RU-58841 shines as a molecule with clear mechanistic rationale and supportive preliminary data. Its strategy of directly targeting and inhibiting DHT’s action at the follicular level presents a compelling narrative for its use in AGA. As the scientific community awaits more extensive clinical trial results, RU-58841 remains an exciting and promising candidate in the battle against hair loss.


  • Battmann, T., Bonfils, A., Branche, C., et al. (1994). RU 58841, a new specific topical antiandrogen: a candidate of choice for the treatment of acne, androgenetic alopecia and hirsutism. Journal of Steroid Biochemistry and Molecular Biology, 48(1), 55-60.
  • Probst, M. R., Beer, M., & Beer, D. (1997). Comparative quantification of IL-1β, IL-10, IL-10r, TNFα and IL-7 mRNA levels in UV-irradiated human skin in vivo. Inflammation Research, 46(12), 483-492.

Note: This piece serves as an informative overview. Individual responses may vary, and consultation with a qualified medical professional is indispensable before initiating any therapeutic regimen.

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