What is the use of Finasteride (Propecia)?

From the Guidelines

Finasteride is a recommended treatment option for benign prostatic hyperplasia (BPH) due to its ability to reduce prostate volume and improve symptoms, as evidenced by a mean difference of -1.9 in IPSS scores 1.

Key Points to Consider

• Finasteride works by inhibiting the 5-alpha-reductase type II isoenzyme, reducing dihydrotestosterone (DHT) levels in the prostate by approximately 80% 1.
• The medication is most effective in men with larger prostates (>30cc) or higher PSA levels (>1.5ng/mL), with a more pronounced effect on glandular epithelial component atrophy 1.
• Patients should be counseled on the slow onset of action, with symptom improvement typically observed after 3-6 months of treatment, and maintained for 6-10 years of follow-up 1.
• Common side effects may include decreased libido, erectile dysfunction, and decreased ejaculate volume, though these occur in a small percentage of users.
• When screening men for prostate cancer who are on finasteride, patients should be informed of alterations in PSA due to the medication, and the measured serum PSA value should be doubled after 1 year of therapy to accurately gauge disease progression 1.

Treatment and Monitoring

• The recommended dose of finasteride for BPH is 5mg daily 1.
• Regular follow-up with a healthcare provider is important to monitor for effectiveness and any adverse effects.
• Combination therapy with alpha-blockers may be considered for men with moderate to severe symptoms, and treatment should be individualized based on prostate volume and PSA threshold 1.
• Imaging with TRUS or cross-sectional imaging may be necessary to objectively assess prostate size and guide treatment decisions 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. Daily dosing of finasteride tablets at 5 mg/day for up to 4 years has been shown to reduce the serum DHT concentration by approximately 70%. The median circulating level of testosterone increased by approximately 10 to 20% but remained within the physiologic range

Finasteride Mechanism and Effects:

• Finasteride works by inhibiting Type II 5α-reductase, an enzyme that converts testosterone to DHT.
• It reduces serum DHT concentration by approximately 70% with daily dosing at 5 mg/day for up to 4 years.
• The median circulating level of testosterone increases by approximately 10 to 20% but remains within the physiologic range 2

From the Research

Finasteride Overview

• Finasteride is primarily used to treat benign prostatic hyperplasia (BPH) and male androgenetic alopecia (MAA) 3.
• It works by inhibiting type 2 5-alpha-reductase activity, significantly reducing dihydrotestosterone levels 4.

Finasteride and Erectile Dysfunction

• There is evidence suggesting that 5-alpha-reductase inhibitors (5α-RIs) may independently increase the risk of erectile dysfunction (ED) 3.
• Most studies found that finasteride for BPH was correlated with ED, while finasteride for MAA was not correlated with ED 3.
• However, some studies reported side effects of finasteride associated with sexual dysfunction, including ED, male infertility, ejaculation problem, and loss of libido, even in MAA patients 3, 5.

Finasteride and Prostate Cancer

• Finasteride has been shown to reduce the incidence of prostate cancer 6.
• The Prostate Cancer Prevention Trial (PCPT) found that finasteride reduced the risk of prostate cancer, but there is controversy surrounding its use due to claims of increased risk for higher grade prostate cancers 7.
• However, a review of the PCPT trial found that finasteride is safe for the treatment of androgenetic alopecia without the concern for the induction of high-grade prostate cancer 7.

Finasteride Side Effects and Safety

• Finasteride is generally well tolerated, with most commonly reported adverse effects being sexually related (1 to 2.1%) 4.
• Gynaecomastia has been reported in 0.4% of patients 4.
• Current evidence on the safety of finasteride indicates that it is safe, but there is growing concern about its sexual side effects 5.
• Proper information should be provided to patients prior to starting treatment, and further studies are required to fully understand the sexual side effects of finasteride 5.