From the Guidelines
Finasteride is primarily used to treat benign prostatic hyperplasia (BPH) and male pattern baldness, with a recommended dose of 5mg daily for BPH and 1mg daily for hair loss, as it inhibits the enzyme 5-alpha-reductase, reducing dihydrotestosterone (DHT) levels and subsequently shrinking the prostate and promoting hair growth. The medication has been shown to improve standardized symptom scores, such as the International Prostate Symptom Score (IPSS), with improvements of 3 to 4 points observed and maintained for 6 to 10 years of follow-up 1.
Mechanism of Action and Effects
Finasteride works by selectively inhibiting the 5-alpha-reductase type II isoenzyme, reducing serum DHT levels by approximately 70% 1. This reduction in DHT leads to a decrease in prostate volume, with studies showing a reduction of 15-25% at six months 1. The medication also affects the levels of prostate-specific antigen (PSA), reducing them by approximately 50%, which is essential to consider when screening for prostate cancer in patients taking finasteride 1.
Treatment Duration and Outcomes
The optimal treatment duration for finasteride has not been directly compared in trials, but the Prostate Cancer Prevention Trial (PCPT) administered finasteride for 7 years, suggesting that this duration may be necessary for primary prevention 1. However, an ongoing trial comparing dutasteride with placebo for preventing prostate cancer may provide further insight into the required treatment duration.
Side Effects and Considerations
Common side effects of finasteride include decreased libido, erectile dysfunction, and decreased ejaculate volume, although these occur in a small percentage of users 1. Women who are pregnant or may become pregnant should not handle crushed tablets due to potential risks to male fetuses. It is essential to discuss any concerns about side effects with a healthcare provider, as most men tolerate the medication well, and for many, the benefits outweigh the potential risks.
Clinical Recommendations
Based on the most recent and highest-quality evidence, finasteride is recommended for the treatment of BPH and male pattern baldness, with careful consideration of the potential side effects and the need for ongoing treatment to maintain benefits. Patients should be informed about the effects of finasteride on PSA levels and the importance of regular monitoring for prostate cancer. The medication should be used under the guidance of a healthcare provider, who can help weigh the benefits and risks and determine the best course of treatment for each individual patient.
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 patients with BPH, finasteride tablets have no effect on circulating levels of cortisol, prolactin, thyroid-stimulating hormone, or thyroxine. These individuals have a small prostate gland throughout life and do not develop BPH In patients with BPH treated with finasteride (1 to 100 mg/day) for 7 to 10 days prior to prostatectomy, an approximate 80% lower DHT content was measured in prostatic tissue removed at surgery, compared to placebo;
The use of Finasteride (Propecia) is for the treatment of Benign Prostatic Hyperplasia (BPH), by reducing the size of the prostate gland.
- Key benefits: Reduces the size of the prostate gland, decreases DHT levels, and increases testosterone levels.
- Main mechanism: Inhibits Type II 5α-reductase, an enzyme that converts testosterone to DHT. 2
From the Research
Use of Finasteride (Propecia)
- Finasteride is primarily used to treat benign prostatic hyperplasia (BPH) and male androgenetic alopecia (MAA) 3, 4.
- It works by inhibiting the conversion of testosterone to dihydrotestosterone (DHT), which acts as the primary androgen in the prostate and hair follicles 3.
- The only FDA-approved dermatological indication of finasteride is androgenetic alopecia 3.
Effects on Prostate Cancer
- Finasteride has been found to be effective in significantly reducing the incidence of low-grade prostate cancer 3.
- However, there is a paradoxical increase in high-grade cancer in the finasteride group, which has been attributed to increased sensitivity and improved performance of prostate-specific antigen levels to detect all grades of prostate cancer 3.
- A study found that finasteride at a dose of 1 mg (Propecia) does not increase the risk of higher grade prostate cancers 5.
Effects on Sexual Function
- Finasteride may cause sexual dysfunction, including erectile dysfunction, male infertility, ejaculation problems, and loss of libido 4.
- However, most studies found that finasteride for MAA was not correlated with erectile dysfunction, while finasteride for BPH was correlated with erectile dysfunction 4.
- Reduction in ejaculatory volume is the only established causal relationship between finasteride and sexual dysfunction 3.
Comparison with Other Treatments
- A pooled analysis of 15 real-world databases found that finasteride was associated with a lower risk of prostate cancer compared to dutasteride in patients with BPH 6.
- However, after propensity score matching, no significant differences were observed for the risk of prostate cancer between finasteride and dutasteride 6.