What is the time to efficacy for finasteride (Propecia)?

From the Guidelines

Finasteride typically takes 3 to 6 months to show noticeable improvements in urinary symptoms for the treatment of benign prostatic hyperplasia (BPH). This is based on 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. The medication works by blocking the conversion of testosterone to dihydrotestosterone (DHT), which is responsible for prostate growth, and this leads to a reduction in androgenic growth and an increase in apoptosis and atrophy, shrinking the organ from 15-25% at six months 1.

Key Points to Consider

• Finasteride selectively inhibits the 5-AR type II isoenzyme, reducing serum levels of DHT by approximately 70% 1
• The reduction of DHT in prostate tissues has been measured at approximately 80% with finasteride 1
• Improvements in urinary symptoms usually begin within 3 to 6 months, with numerically improvements of 3 to 4 points observed and maintained for 6 to 10 years of follow-up 1
• Patients should be counseled on a slower symptom improvement if treated with 5-ARI alone, compared to alpha blockers 1

Important Considerations for Treatment

• Finasteride is typically prescribed at 5mg daily for BPH (Proscar) 1
• Treatment with 5-ARIs and combination therapy hinges on prostate volume and PSA threshold; therefore, obtaining imaging with TRUS (or reviewing existing cross-sectional imaging) to objectively assess prostate size is reasonable 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 1

From the FDA Drug Label

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

The time to efficacy for finasteride (Propecia) is 8 hours after the first dose, with the suppression of DHT maintained throughout the 24-hour dosing interval and with continued treatment 2.

• Key points:
  • Maximum effect observed 8 hours after the first dose
  • Suppression of DHT maintained throughout the 24-hour dosing interval
  • Continued treatment maintains the suppression of DHT
• Note: The exact time to clinical efficacy (e.g. improvement in symptoms) is not specified in the provided drug label.

From the Research

Time to Efficacy for Finasteride (Propecia)

• The time to efficacy for finasteride can be assessed based on several studies, including a 1999 study published in the journal Drugs, which reported that oral finasteride 1 mg/day promotes hair growth and prevents further hair loss in a significant proportion of men with male pattern hair loss 3.
• In this study, evidence suggested that the improvement in hair count reported after 1 year is maintained during 2 years' treatment, with 48% of finasteride recipients showing improvement in hair growth at 1 year and 66% at 2 years compared with 7% of placebo recipients at each time point.
• Another study published in 2024 in The Journal of Dermatology found that finasteride 1 mg every other month regimen showed similar maintenance effects to the daily regimen, with changes in global photographic assessment in the second year being 1.33 and 1.29 for the daily and every other month groups, respectively 4.
• A 2015 study published in Dermatologic Therapy reported that finasteride at 1 mg/day showed improvement in 80.5% of men treated with finasteride at 12 months, while the combined medication of finasteride and 5% minoxidil showed improvement in 94.1% of men 5.
• The studies suggest that the time to efficacy for finasteride can range from a few months to a year or more, with continued treatment leading to maintained or improved efficacy 3, 4, 5.
• It is worth noting that individual responses to finasteride may vary, and factors such as the severity of hair loss, age, and genetic predisposition may influence the time to efficacy and overall response to treatment 6.