How Finasteride (Propecia) Works, Results, Usage, and Side Effects

The pharmacological intervention against androgenic alopecia (AGA), or male-pattern baldness, has seen significant advancements in recent decades. Among the prime movers in this therapeutic frontier is Finasteride (brand name Propecia). A deep dive into its mechanism, backed by scientific studies, offers insights into its prominent role in combatting hair loss.

Box of Propecia 1mg pills at Hairloss-Recovery fda approved treatments

What is Finasteride?

Finasteride is an oral medication used for the treatment of hair loss, specifically male pattern baldness (androgenetic alopecia) in men. It belongs to a class of drugs known as 5-alpha-reductase inhibitors. The key role of finasteride is to inhibit the action of the enzyme 5-alpha-reductase, which converts testosterone into dihydrotestosterone (DHT). DHT is a hormone that can shrink hair follicles and lead to hair thinning and eventual hair loss in genetically susceptible individuals. By blocking the conversion of testosterone into DHT, finasteride helps to maintain and sometimes even regrow hair in men with male pattern baldness. It is available in tablet form and typically requires a prescription from a healthcare provider.

History of Finasteride

The history of finasteride is a story of scientific discovery and pharmaceutical innovation. In the 1970s and 1980s, researchers at Merck & Co., Inc. embarked on a journey to develop medications for conditions like benign prostatic hyperplasia (BPH), a non-cancerous enlargement of the prostate gland that affects many older men. It was during this period that they identified finasteride as a promising compound.

In 1985, Merck researchers made a breakthrough by pinpointing finasteride’s ability to inhibit the enzyme 5-alpha-reductase. This enzyme plays a crucial role in the conversion of testosterone into dihydrotestosterone (DHT), a hormone associated with prostate growth and male pattern baldness. The discovery of finasteride’s action paved the way for its development as a potential treatment for both BPH and hair loss.

By 1992, after rigorous clinical trials to assess safety and efficacy, Merck received FDA approval to market finasteride as Proscar for the treatment of BPH. This marked the beginning of its journey in addressing prostate-related issues. Subsequently, in 1997, Merck gained another significant achievement with the FDA’s approval of a lower-dose version of finasteride known as Propecia. Propecia became the first oral medication sanctioned for the treatment of male pattern baldness, making it a groundbreaking solution for millions of men experiencing hair loss.

Since then, finasteride, available in the forms of Proscar and Propecia, has become a widely prescribed medication for BPH and male pattern baldness. Its history reflects the pharmaceutical industry’s commitment to developing innovative treatments for common health concerns, ultimately improving the quality of life for many individuals. However, it’s important for users to approach finasteride with awareness of its benefits and potential side effects and to consult healthcare professionals for informed decision-making.

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 Finasteride Works

Finasteride treats hair loss, specifically male pattern baldness (androgenetic alopecia), by addressing one of the key underlying factors: the hormone dihydrotestosterone (DHT). Here’s how finasteride works to combat hair loss:

  • Inhibition of 5-Alpha-Reductase: The primary mechanism involves inhibiting the action of the enzyme 5-alpha-reductase. This enzyme plays a critical role in the conversion of testosterone, a male sex hormone, into dihydrotestosterone (DHT). DHT is a potent hormone that can shrink hair follicles in individuals genetically susceptible to hair loss. As a result, hair becomes thinner, shorter, and eventually stops growing.
  • Reduction of DHT Levels: By inhibiting 5-alpha-reductase, it significantly reduces the levels of DHT in the scalp and bloodstream. Lower DHT levels lead to a less detrimental effect on hair follicles. Hair follicles can then potentially recover and continue producing healthy hair.
  • Promotion of Hair Regrowth: With the reduction of DHT’s influence, it can help reverse the miniaturization of hair follicles. Miniaturization is the process by which hair follicles become progressively smaller and produce finer, shorter hairs. By slowing or stopping this process, finasteride allows for the regrowth of thicker, longer, and healthier hair.

It’s important to note that it is typically taken as a daily oral medication. While it can be effective in promoting hair regrowth, its results may vary among individuals, and it is not a cure for hair loss. Additionally, its effects are usually most noticeable on the crown and top of the head, and it may not be as effective for receding hairlines. It’s essential to consult a healthcare provider or dermatologist before starting treatment to discuss its suitability, potential side effects, and expected outcomes.

Empirical Evidence

  • Pivotal Clinical Trials: A landmark double-blind placebo-controlled study over two years, encompassing over 1,500 men with AGA, revealed that Finasteride users experienced significant improvements in both scalp hair count and perceived hair density, compared to the placebo group.
  • Extended Efficacy Analyses: Subsequent research spanning five years reinforced Finasteride’s enduring efficacy. Here, not only was the progression of hair loss arrested in a majority of participants, but a substantial fraction also documented appreciable hair regrowth.
  • Biochemical and Histological Evidence: Biopsies from participants of clinical trials showcased a notable increase in the number of anagen hair follicles in Finasteride-treated scalps. Simultaneously, DHT concentration measurements validated the drug’s inhibitory effect on the androgen.
Clinical results of finasteride trials showing improvement in hair loss

Improved hair growth and density after 6 months of continued finasteride use.


The results of finasteride can vary from person to person, and it’s important to manage expectations when using this medication for hair loss. Here are some general outcomes associated with finasteride use:

  • Slowed Hair Loss: Finasteride is often effective at slowing down the progression of male pattern baldness (androgenetic alopecia). It can help prevent further hair loss in many individuals, which is an important benefit.
  • Hair Regrowth: Some individuals may experience partial hair regrowth while using finasteride. This regrowth typically occurs in areas where hair follicles have become miniaturized but are not yet completely dormant. It may result in thicker and longer hair.
  • Improved Hair Thickness: Even without significant regrowth, many users report that their existing hair becomes thicker and healthier while on finasteride. This can contribute to a more aesthetically pleasing appearance.
  • Maintenance of Hair: For some users, finasteride helps maintain their current hairline and density, preventing further thinning or balding.
  • Visible Results Over Time: It’s important to note that results with finasteride are not immediate. It usually takes several months, typically around three to six months or even longer, to notice any significant changes in hair density or regrowth.
  • Variable Responses: Not everyone responds to finasteride in the same way. While many users see positive results, others may experience limited improvement or no change in their hair loss.
  • Continued Use Required: To maintain the benefits of finasteride, individuals typically need to continue taking the medication indefinitely. Discontinuing its use may lead to the gradual return of hair loss.
Before and after results of using finasteride to treat hair loss

Improved hair growth and density after 6 months of continued finasteride use.

How to Use

Finasteride is typically taken as an oral medication to treat male pattern baldness (androgenetic alopecia). Here are general guidelines on how to use finasteride:

  • Consult a Healthcare Provider: Before starting finasteride, it’s crucial to consult with a healthcare provider, preferably a dermatologist or a healthcare professional experienced in hair loss treatment. They will assess your specific condition and determine if finasteride is a suitable option for you.
  • Prescription: Finasteride is available by prescription only. If your healthcare provider recommends it, they will write a prescription for the medication.
  • Dosage: The standard dosage of finasteride for male pattern baldness is 1 milligram (mg) per day. This is the dosage typically prescribed to slow hair loss and promote regrowth. It is available in tablet form.
  • Consistency: Take finasteride at the same time each day to maintain consistent levels of the medication in your system. It can be taken with or without food.
  • Follow Your Healthcare Provider’s Instructions: Always follow your healthcare provider’s instructions for using finasteride. Do not take more or less than the prescribed dose, and do not stop taking it without consulting your healthcare provider.
  • Be Patient: Finasteride takes time to produce noticeable results. It can take several months, often three to six months or longer, before you see significant changes in hair density or regrowth. Continuously taking the medication is essential for maintaining its benefits.
  • Regular Follow-Up: Your healthcare provider may schedule regular follow-up appointments to monitor your progress and assess the effectiveness of finasteride in your case. These appointments are essential to ensure the medication is working as intended.
  • Continued Use: To maintain the benefits of finasteride, you typically need to continue taking the medication indefinitely. Discontinuing its use may lead to the gradual return of hair loss.

Safety and Side Effects

Finasteride, a medication used to treat male pattern baldness (androgenetic alopecia) and benign prostatic hyperplasia (enlarged prostate), may have side effects. It’s essential to be aware of potential side effects and discuss them with your healthcare provider before starting the medication. Common side effects of finasteride include:

  • Sexual Side Effects: Some users may experience sexual side effects, which can include decreased libido, erectile dysfunction, and ejaculation disorders. These side effects can be concerning for some individuals and may persist even after discontinuing the medication in rare cases.
  • Breast Tenderness or Enlargement: Some users may notice breast tenderness or an increase in breast size (gynecomastia). This side effect is typically reversible upon discontinuation of finasteride.
  • Allergic Reactions: Although rare, some individuals may experience allergic reactions to finasteride, such as rash, itching, swelling, severe dizziness, or difficulty breathing. Seek immediate medical attention if you suspect an allergic reaction.
  • Depression and Mood Changes: In some cases, finasteride has been associated with mood changes, including symptoms of depression and anxiety. If you experience significant changes in mood or emotional well-being while taking the medication, consult your healthcare provider.
  • Other Less Common Side Effects: Some users may report less common side effects, including testicular pain, testicular swelling, and general discomfort in the genital area.


Finasteride’s molecular action, centered around the inhibition of DHT synthesis, offers a compelling and scientifically validated approach to combatting AGA. Its success story, underpinned by a combination of biochemical, histological, and clinical evidence, cements its role as a cornerstone in AGA therapy.


  • Kaufman, K.D., et al. (1998). Finasteride in the treatment of men with androgenetic alopecia. Journal of the American Academy of Dermatology, 39(4), 578-589.
  • Leyden, J., et al. (2004). Finasteride in the treatment of clinical benign prostatic hyperplasia: A systematic review of randomized trials. BMC Urology, 4(15), 22-30.
  • Whiting, D.A. (2001). Male pattern hair loss: Current understanding. International Journal of Dermatology, 40(8), 469-477.
  • Olsen, E.A., et al. (2002). The importance of dual 5α-reductase inhibition in the treatment of male pattern hair loss. Journal of the American Academy of Dermatology, 46(6), 856-862.

Note: Always seek professional medical advice before starting any treatment.

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