What is the use of Finasteride (Propecia)?

From the Guidelines

Finasteride is an effective treatment for benign prostatic hyperplasia (BPH) and can reduce the risk of subsequent acute urinary retention and the need for BPH-related surgery, particularly in patients with enlarged prostates or higher PSA values. The medication works by inhibiting the enzyme 5-alpha reductase, which converts testosterone to dihydrotestosterone (DHT), a hormone that contributes to prostate enlargement 1.

Key Points

• Finasteride can reduce the size of the prostate, increase peak urinary flow rate, and reduce BPH symptoms, with an average patient experiencing a 3-point improvement in the AUA Symptom Index 1.
• The medication is ineffective for relief of lower urinary tract obstructive symptoms in patients who do not have enlarged prostates 1.
• Reported adverse events are primarily sexually related, including decreased libido, ejaculatory dysfunction, and erectile dysfunction, which are reversible and uncommon after the first year of therapy 1.

Treatment Considerations

• Finasteride is not appropriate treatment for men with LUTS who do not have any prostatic enlargement 1.
• The absolute benefit of finasteride increases with rising prostate volume or serum PSA, making it a more effective treatment option for patients with larger prostates or higher PSA values 1.

From the FDA Drug Label

The development and enlargement of the prostate gland is dependent on the potent androgen, 5α -dihydrotestosterone (DHT). Finasteride is a competitive and specific inhibitor of Type II 5α-reductase with which it slowly forms a stable enzyme complex. In man, a single 5-mg oral dose of finasteride tablets produces a rapid reduction in serum DHT concentration, with the maximum effect observed 8 hours after the first dose.

Mechanism of Action: Finasteride works by inhibiting the conversion of testosterone to 5α-dihydrotestosterone (DHT) through its action on Type II 5α-reductase.

• It forms a stable enzyme complex with Type II 5α-reductase, leading to a decrease in DHT levels.
• The reduction in DHT levels leads to a decrease in the development and enlargement of the prostate gland.
• Daily dosing of finasteride at 5 mg/day reduces serum DHT concentration by approximately 70% 2.

From the Research

Finasteride Overview

• Finasteride is a type 2-selective 5alpha-reductase inhibitor used to treat men with androgenetic alopecia (male pattern hair loss) and benign prostatic hyperplasia (BPH) 3.
• It was approved in 1997 as the first oral pharmacologic therapy for the treatment of men with androgenetic alopecia 3.

Efficacy and Safety

• Finasteride has a well-established, excellent safety profile, and subsequent studies demonstrated that it is an effective treatment for men with androgenetic alopecia at an optimal dose of 1 mg/day 3.
• The drug can reduce the size of the prostate gland by about 20% and the level of prostate-specific antigen (PSA) by about 50% 4.
• Finasteride can also be used to stop male baldness, particularly effective in men aged 20-40 years, with 85% of patients stopping hair loss when given the drug 4.

Side Effects

• Common side effects of finasteride include impotence, decreased ejaculatory volume, and gynaecomastia 4.
• There is evidence suggesting that 5α-RIs, such as finasteride, may independently increase the risk of erectile dysfunction (ED) 5.
• However, most studies found that finasteride for male androgenetic alopecia was not correlated with ED, while finasteride for BPH was correlated with ED 5.
• Post-marketing reports have led to the inclusion of depression in the FDA label, as men were found to be at a risk of suicide due to persistent sexual side effects, commonly termed as post-finasteride syndrome 6.

Mechanism of Action

• Finasteride inhibits the Type II isoform of the 5alpha-reductase enzyme, which is the predominant form in human prostate and hair follicles, and reduces the conversion of testosterone to dihydrotestosterone (DHT) 7.
• The reduction of DHT leads to a decrease in the size of the prostate gland and an increase in hair growth 7.
• Finasteride also affects the levels of neuroactive steroids, which have rapid non-genomic effects on brain function and behavior 7.