What is the typical time frame for finasteride (Finasteride) to show its effects for benign prostatic hyperplasia (BPH) and androgenetic alopecia?

From the Guidelines

Finasteride typically takes 3-6 months to show its effects for benign prostatic hyperplasia (BPH) and 3-12 months for androgenetic alopecia. The medication works by inhibiting the enzyme 5-alpha reductase, which converts testosterone to dihydrotestosterone (DHT), the hormone responsible for prostate enlargement and hair follicle miniaturization 1. For BPH, patients may experience improved urinary flow and reduced symptoms like frequent urination within the first few months, with maximum benefits often achieved by 6 months. This is supported by numerous robust analyses of randomized, placebo-controlled trials with finasteride, which have shown an improvement in standardized symptom scores (eg, IPSS) superior to placebo 1.

Some key points to consider when using finasteride include:

• The standard dose is 5mg daily for BPH and 1mg daily for hair loss
• Patients should understand that continuous treatment is necessary to maintain benefits, as stopping the medication will allow DHT levels to rise again, causing symptoms to return within 6-12 months
• Side effects may include sexual dysfunction in a small percentage of users
• When screening men for prostate cancer who are on 5-ARIs, patients should be informed of alterations in PSA due to the medication, and after 1 year of 5-ARI therapy, the measured serum PSA value should be doubled to accurately gauge disease progression 1

It's also important to note that the effectiveness of finasteride can vary depending on the individual and the severity of their condition. Treatment with 5-ARIs and combination therapy hinges on prostate volume and PSA threshold, and obtaining imaging with TRUS (or reviewing existing cross-sectional imaging) to objectively assess prostate size is reasonable, with reservation of 5-ARIs for those with appropriately enlarged glands 1. A minimum prostate volume of >30cc or PSA >1.5ng/mL is necessary for a reliable 5-ARI response, but the larger the gland, the more pronounced the effects.

From the FDA Drug Label

Finasteride has no affinity for the androgen receptor In man, the 5α-reduced steroid metabolites in blood and urine are decreased after administration of finasteride. 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. The suppression of DHT is maintained throughout the 24-hour dosing interval and with continued treatment 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%. In healthy male volunteers treated with finasteride tablets for 14 days, discontinuation of therapy resulted in a return of DHT levels to pretreatment levels in approximately 2 weeks. In patients treated for three months, prostate volume, which declined by approximately 20%, returned to close to baseline value after approximately three months of discontinuation of therapy.

The effects of finasteride can be seen as early as 8 hours after the first dose, with a rapid reduction in serum DHT concentration.

• The maximum effect is observed 8 hours after the first dose.
• The suppression of DHT is maintained throughout the 24-hour dosing interval and with continued treatment.
• It may take up to 4 years of daily dosing to achieve the full effect of approximately 70% reduction in serum DHT concentration.
• If therapy is discontinued, DHT levels return to pretreatment levels in approximately 2 weeks, and prostate volume returns to close to baseline value after approximately three months 2.

From the Research

Time Frame for Finasteride to Show Effects

• For benign prostatic hyperplasia (BPH), finasteride typically takes at least 6 months to show its effects, with significant improvements in peak urinary flow rate and urological symptoms 3.
• A study found that the maximum efficacy of finasteride is obtained within 6 months and maintained over 6 years, with a decrease in prostate size of around 27% at 6 months and an improvement in urinary flow rate of 2.4 ml/s 4.
• Another study confirmed that finasteride causes long-term symptomatic improvement and reduces the risk of acute urinary retention or surgery, with significant improvements in total symptom score, obstructive symptom score, maximal urinary flow rate, and prostate volume at 12 and 24 months 5.

Effects on Androgenetic Alopecia

• Finasteride is also used to treat androgenetic alopecia (male pattern hair loss), with an optimal dose of 1 mg/day, and has a well-established, excellent safety profile 6.
• The effects of finasteride on androgenetic alopecia may take several months to become apparent, with long-term use (up to 5 years) showing significant improvements in hair growth and density.

Overall Efficacy and Safety

• Finasteride is generally well-tolerated, with most adverse events related to sexual dysfunction, such as decreased libido, ejaculation disorders, and impotence, occurring in a small proportion of patients (about 2 to 3%) 3, 7.
• The benefits of finasteride therapy appear to outweigh the risks, with significant improvements in symptoms and quality of life for patients with BPH and androgenetic alopecia 3, 5.