From Oral to Topical Application: Research and Breakthroughs in Finasteride Treatment for Hair Loss and Its Impact on Sexual Dysfunction

I. Introduction

1.1 Research Background and Significance

Hair loss has become an increasingly serious problem in today’s society, significantly affecting the quality of life and mental health of patients. According to relevant data, the number of people with hair loss worldwide is on the rise year by year. Androgenetic alopecia is the most common type, accounting for more than 70% of the total number of hair loss patients. In the United States, the incidence of androgenetic alopecia is also relatively high, with a prevalence of about 21.3% in men and 6.0% in women. Hair loss not only affects personal appearance but may also lead to psychological problems such as low self – esteem and anxiety in patients, reducing their social and professional competitiveness.

Oral finasteride, as a first – line drug for the treatment of androgenetic alopecia, has been widely used in clinical practice. Its mechanism of action is mainly to inhibit the activity of 5α – reductase, reducing the conversion of testosterone to dihydrotestosterone (DHT), thereby reducing the damage of DHT to hair follicles and promoting hair growth. However, while treating hair loss, oral finasteride also causes a series of adverse reactions, among which sexual dysfunction is one of the most prominent problems. According to multiple studies, the incidence of sexual dysfunction caused by oral finasteride ranges from 1.8% to 15%, with specific manifestations including decreased libido, erectile dysfunction, ejaculatory dysfunction, etc. These adverse reactions not only seriously affect the patient’s quality of life but also lead many patients to discontinue treatment due to intolerance, greatly reducing the effectiveness of hair loss treatment.

Therefore, finding a treatment method that can effectively treat hair loss while avoiding or reducing adverse reactions such as sexual dysfunction has important clinical significance and social value. Topical finasteride, as a new treatment method, delivers the drug directly to the scalp hair follicles through local administration, reducing the systemic absorption of the drug. Theoretically, it can reduce the risk of adverse reactions such as sexual dysfunction. At the same time, topical finasteride also has the advantages of convenient use and high patient compliance, providing a new treatment option for hair loss patients. Studying the application of topical finasteride in hair loss treatment is of great practical significance for improving the treatment effect and quality of life of hair loss patients.

1.2 Research Objectives

This study aims to deeply explore the effect of topical finasteride in hair loss treatment and its feasibility in solving the sexual dysfunction problem caused by oral finasteride. Specifically, through a comprehensive analysis of relevant literature, detailed research on clinical cases, and a comparative study with oral finasteride, the efficacy, safety, and tolerability of topical finasteride will be evaluated, and its position and advantages in hair loss treatment will be clarified. At the same time, explore the optimal usage method and dosage of topical finasteride, provide a scientific basis for clinical treatment, help hair loss patients get rid of hair loss troubles while avoiding or reducing the occurrence of adverse reactions such as sexual dysfunction, and improve their quality of life.

1.3 Research Methods and Innovations

This study mainly adopts the following research methods:

• Literature Research Method: Systematically search relevant domestic and foreign databases such as PubMed, Web of Science, and CNKI to collect research literature on the treatment of hair loss with topical finasteride and the adverse reactions of oral finasteride. Comprehensively sort out and analyze these literatures, summarize the achievements and deficiencies of existing research, and provide a theoretical basis and research ideas for this study.
• Case Analysis Method: Collect cases of patients who have used topical finasteride to treat hair loss in clinical practice, and record in detail the patients’ treatment processes, curative effects, and adverse reaction situations. Through in – depth analysis of these cases, further understand the actual application effect and safety of topical finasteride, and provide a clinical basis for the research conclusions.
• Comparative Research Method: Compare the topical finasteride treatment group with the oral finasteride treatment group, and compare the differences between the two groups in terms of treatment effect, incidence of adverse reactions, etc. Through comparative research, clarify the advantages of topical finasteride in solving the problem of sexual dysfunction, and provide a more persuasive reference for clinical treatment.

The innovation of this study lies in focusing on solving the dual problems of hair loss and sexual dysfunction for the first time, and conducting a comprehensive and in – depth study on the application of topical finasteride. Compared with previous studies, it not only pays attention to the treatment effect of topical finasteride but also focuses on exploring its role in avoiding sexual dysfunction, providing a new research perspective and direction for the field of hair loss treatment. At the same time, by comprehensively using a variety of research methods and conducting research from multiple levels such as theory, clinical practice, and comparative analysis, the research results are more comprehensive, accurate, and reliable, providing more guiding suggestions for clinical treatment.

II. Current Situation of Oral Finasteride in Treating Hair Loss and Causing Sexual Dysfunction

2.1 Principles and Efficacy of Oral Finasteride in Treating Hair Loss

The principle of oral finasteride in treating hair loss is based on the pathogenesis of androgenetic alopecia. Androgenetic alopecia is mainly closely related to the body’s androgen testosterone and its metabolite dihydrotestosterone (DHT). In the scalp hair follicles of patients with androgenetic alopecia, there is a highly active 5α – reductase, which can catalyze the conversion of testosterone to DHT. DHT has strong androgenic activity and has a higher affinity for androgen receptors in hair follicle cells. The combination of the two will lead to miniaturization of hair follicles, shortening of the growth period, and prolongation of the resting period. Eventually, the hair gradually becomes thinner, softer, and falls out.

Oral finasteride is a specific type II 5α – reductase inhibitor. Its mechanism of action is to tightly bind to the active site of type II 5α – reductase to form a stable complex, thereby competitively inhibiting the activity of 5α – reductase. This inhibitory effect blocks the conversion process of testosterone to DHT, thus significantly reducing the levels of DHT in serum and local scalp. Low levels of DHT cannot fully bind to androgen receptors in hair follicle cells, thus avoiding the miniaturization and atrophy of hair follicles and creating favorable conditions for normal hair growth. In addition, finasteride may also improve the micro – environment of hair follicles by regulating angiogenesis and cytokine expression around hair follicles, further promoting hair growth.

A large number of clinical studies and practical data have fully confirmed the significant efficacy of oral finasteride in the treatment of androgenetic alopecia. In a large – scale, multi – center, randomized, double – blind, placebo – controlled trial involving 515 male patients with androgenetic alopecia, the patients were randomly divided into two groups, receiving 1mg of finasteride daily and placebo treatment respectively, with a treatment course of 24 months. The results showed that at 12 months of treatment, the hair count in the finasteride treatment group increased by an average of 19 hairs/cm² compared to the baseline, while the placebo group decreased by an average of 1 hair/cm². At 24 months of treatment, the hair count in the finasteride treatment group increased by an average of 25 hairs/cm² compared to the baseline, and the placebo group decreased by an average of 4 hairs/cm². In terms of subjective evaluation, after 24 months of treatment, 77% of the patients in the finasteride treatment group considered that their hair loss had improved, while only 15% in the placebo group.

Another study conducted a 5 – year long – term follow – up observation on 1879 male patients with androgenetic alopecia. The results showed that in patients who continuously used finasteride for treatment, the number of hairs continued to increase within 5 years, and the quality and diameter of the hair also improved. The hair loss symptoms of these patients were effectively controlled, the appearance of the hair was significantly improved, and the quality of life was significantly enhanced. In addition, a number of clinical studies have also found that the treatment effect of oral finasteride has a certain dose – dependence. Within the recommended dose range (1mg/d), the curative effect gradually increases with the prolongation of the treatment time.

In summary, oral finasteride effectively treats androgenetic alopecia by inhibiting the activity of 5α – reductase and reducing the level of DHT. Its efficacy has been fully verified in long – term clinical practice, bringing hope to many hair loss patients.

2.2 Case Analysis of Sexual Dysfunction Caused by Oral Finasteride

In clinical practice, cases of sexual dysfunction caused by oral finasteride are not uncommon. The following will list several representative cases in detail:

• Case 1: Patient A, a 32 – year – old male, started taking oral finasteride at a daily dose of 1mg due to androgenetic alopecia. After taking the medicine for about 1 month, the patient began to experience symptoms of decreased libido, with a significant reduction in interest in sexual life. The frequency of sexual life decreased from 3 – 4 times a week to 1 – 2 times a week. At the same time, erectile function was also affected. The erection hardness was not as good as before, and sometimes it was even difficult to achieve a satisfactory erection state, resulting in a serious decline in the quality of sexual life. After the appearance of these symptoms, the patient’s mental pressure gradually increased, and the anxiety became more and more serious. He was seriously worried about his sexual function. After continuing to take the medicine for 3 months, the patient’s sexual dysfunction symptoms did not improve, so he stopped taking the medicine on his own. After stopping the medicine, it took about 2 months for the symptoms of decreased libido and erectile dysfunction to gradually ease, but they still did not fully return to the level before taking the medicine.
• Case 2: Patient B, a 28 – year – old male, also took oral finasteride for androgenetic alopecia. About 2 months after taking the medicine, the patient developed ejaculatory dysfunction, manifested as a significant reduction in ejaculation volume and a significant decrease in the pleasure during ejaculation. In addition, there were also problems of decreased libido and erectile dysfunction. These sexual dysfunction symptoms brought great distress to the patient, making him feel inferior and depressed in sexual life, and thus affecting his relationship with his partner. After the appearance of symptoms, the patient consulted a doctor. However, due to concerns that stopping the medicine would affect the hair loss treatment effect, he continued to take the medicine under the doctor’s advice. However, as the medication time prolonged, the sexual dysfunction symptoms not only did not improve but showed a trend of aggravation. After taking the medicine for 6 months, the patient finally decided to stop taking it. After stopping the medicine, after a period of conditioning and recovery, the symptoms of ejaculatory dysfunction and decreased libido gradually decreased, but the problem of erectile dysfunction still persisted, having a negative impact on the patient’s life.
• Case 3: Patient C, a 35 – year – old male, developed severe erectile dysfunction after taking oral finasteride for hair loss treatment for 3 months, and could hardly complete normal sexual life. At the same time, libido also decreased significantly, and the response to sexual stimulation became dull. After discovering these problems, the patient immediately stopped taking the medicine, but the symptoms of erectile dysfunction and decreased libido did not improve significantly after stopping the medicine. After further examination and evaluation, it was found that the patient’s sex hormone levels had changed, with a decrease in testosterone levels, and the DHT level did not return to the normal range. During the subsequent treatment process, the patient received psychological counseling and drug treatment, but the problem of sexual dysfunction still persisted for a long time, causing great harm to the patient’s physical and mental health.

From the above cases, it can be seen that the sexual dysfunction caused by oral finasteride is diverse and has individual differences. The symptoms and severity that different patients experience are different. These cases also indicate that sexual dysfunction has a serious negative impact on the patient’s quality of life and mental health. Many patients often fall into negative emotions such as anxiety and depression when facing the problem of sexual dysfunction, and even have a resistant psychology towards hair loss treatment. Therefore, it is urgent to find a treatment method that can effectively treat hair loss while avoiding or reducing the adverse reaction of sexual dysfunction.

III. Research Progress of Topical Finasteride

3.1 Principles and Advantages of Topical Finasteride in Treating Hair Loss

The principle of topical finasteride in treating hair loss is the same as that of oral finasteride, both by inhibiting the activity of 5α – reductase and reducing the conversion of testosterone to dihydrotestosterone (DHT). There are mainly two isozymes of 5α – reductase in the human body, namely type I and type II, and type II 5α – reductase plays a key role in the pathogenesis of androgenetic alopecia. Topical finasteride can specifically inhibit type II 5α – reductase, preventing the conversion of testosterone to DHT in the local scalp, thereby reducing the local DHT level in the scalp. The reduction of DHT level can reduce its toxic effect on hair follicles, gradually restore the health of hair follicles, promote hair growth, and ultimately achieve the purpose of treating hair loss.

Compared with oral finasteride, topical finasteride has significant advantages, the most prominent of which is its ability to reduce the systemic exposure of the drug. After oral finasteride enters the human body, it is absorbed through the gastrointestinal tract, then enters the blood circulation, and is distributed to various tissues and organs of the body. In this process, the drug not only acts on the scalp hair follicles but also affects other parts of the body, which increases the risk of adverse reactions, especially systemic adverse reactions such as sexual dysfunction. While topical finasteride is directly applied to the surface of the scalp, and through local absorption of the scalp, it acts on the hair follicles. The drug is mainly concentrated in the local scalp to play a role, and the amount entering the blood circulation is extremely small. Relevant studies have shown that after topical application of finasteride, its concentration in plasma is significantly lower than that of oral finasteride, and the average maximum systemic exposure is more than 100 times lower than that of oral finasteride. This means that topical finasteride has minimal impact on the body’s endocrine system, thus greatly reducing the risk of adverse reactions such as sexual dysfunction.

In addition, topical finasteride also has the advantages of convenient use and high patient compliance. Patients only need to directly apply the drug to the scalp, without the need to take it on time like oral drugs. This is more convenient and feasible for some patients who are busy at work or prone to forgetting to take medicine. At the same time, topical finasteride avoids adverse reactions such as gastrointestinal discomfort that may be caused by oral drugs, further improving the patient’s treatment experience and compliance. In summary, topical finasteride has unique advantages in the treatment of hair loss, providing a safer and more effective treatment option for hair loss patients.

3.2 Clinical Research Results of Topical Finasteride

3.2.1 Experimental Design and Methods

In order to deeply study the effect and safety of topical finasteride in treating hair loss, many researchers have carried out a series of rigorous clinical trials. Take a multi – center, randomized, double – blind, placebo – controlled phase III clinical trial carried out in Europe as an example. This trial aimed to evaluate the efficacy and safety of a 0.25% topical finasteride spray in the treatment of male androgenetic alopecia. A total of 458 adult male patients with androgenetic alopecia were included in the study, and they were randomly assigned to three treatment groups according to a ratio of 2:2:1: the topical finasteride spray and oral placebo group (topical finasteride group), the topical placebo and oral placebo group (placebo group), and the topical placebo and oral finasteride (1mg/d) group (oral finasteride group).

In terms of the method of drug use, all patients carried out local spraying on the dry scalp every morning. The topical finasteride group used a 0.25% finasteride spray. Depending on the degree of hair loss, the spray was applied 1 – 4 times (50 – 200µL of solution) each time. The first spray was on a 1 – square – centimeter circular area at the vertex of the scalp, which was marked with a small dot tattoo for repeated efficacy evaluation. If the hair loss area was large, additional sprays (2 – 4 times) could be used to cover the rest of the bald area according to the recommendation of the research doctor. The topical spray needed to be left on the scalp for at least 6 – 8 hours and then washed off with shampoo. The placebo group used a placebo spray containing the same excipients as the finasteride spray but without finasteride. The oral finasteride group took 1mg of finasteride tablets orally every day.

The main observation index of this trial was the change in the target area hair count (TAHC) compared to the baseline at the 24th week. At the same time, the safety indicators of the patients were comprehensively monitored, including the occurrence of adverse events, laboratory test indicators (such as blood routine, liver and kidney function, sex hormone levels, etc.), and skin irritation reactions. In addition, the concentrations of finasteride, testosterone, and dihydrotestosterone (DHT) were measured to evaluate the pharmacokinetic and pharmacodynamic characteristics of the drug. Throughout the trial process, the principles of randomization, double – blindness, and control were strictly followed to ensure the scientificity and reliability of the trial results.

Similar clinical trials have also been carried out in China. A multi – center, randomized, double – blind, placebo – controlled phase III clinical trial aimed to evaluate the efficacy and safety of a topical finasteride spray (CU – 40102) in Chinese adult male patients with androgenetic alopecia. A total of 270 Chinese adult male subjects with androgenetic alopecia were enrolled in this trial. They were also randomly divided into a topical finasteride spray group and a placebo group. The topical finasteride spray group applied the drug topically to the scalp once a day, and the placebo group was given a placebo with the same appearance and usage method. The trial period was 24 weeks, and the main observation indicators were the improvement of the total hair count and terminal hair count in the top bald target area after 24 weeks of treatment. At the same time, the safety of the subjects was closely monitored, including recording adverse events, conducting laboratory tests, and evaluating the local tolerance of the administration site.