Finasteride (often prescribed in a 1mg daily dose) is one of the most effective oral treatments available for male pattern baldness (androgenetic alopecia). It operates by inhibiting the enzyme 5-alpha reductase, which significantly reduces the conversion of testosterone into the potent androgen, Dihydrotestosterone (DHT)—the primary hormone responsible for shrinking susceptible hair follicles. But before committing to a daily pill, it is essential to look beyond marketing claims and examine the robust, long-term clinical data concerning both its remarkable efficacy and the documented risks of side effects.
1. The Core Efficacy: A Decade of Proven Results
Finasteride doesn’t just halt hair loss; for many men, it effectively reverses it. Clinical trials track hair growth using hair counts, global photographic assessment, and investigator evaluations over many years. The data consistently demonstrates the drug’s enduring power.
- 5-Year Data: In multinational studies following men with male pattern baldness over five years, treatment with 1mg finasteride led to durable improvements in scalp hair growth and, critically, slowed the further progression of hair loss that occurred in the placebo groups. After five years, 86% of men in one study either maintained their hair count or experienced hair regrowth, compared to only 43% in the placebo group.
2. Mechanism of Action: Striking at the Root of Hair Loss
The reason for this high efficacy is the drug’s targeted action. By inhibiting the Type II 5-alpha reductase enzyme, finasteride reduces scalp DHT levels by roughly 60% to 70%. This reduction effectively removes the primary trigger for follicular miniaturization (shrinking), allowing genetically susceptible hair follicles to recover and grow thicker, longer, and faster. This foundational mechanism is what makes finasteride so much more powerful than topical treatments alone.
3. The Common Risk: Sexual Side Effects
The most widely discussed side effect of finasteride involves sexual function. Because DHT plays a role in regulating sexual function, some men may experience changes. However, the true prevalence in large clinical trials is often lower than widely publicized reports might suggest.
- Clinical Trial Statistics: Pooled analysis of major clinical trials showed that the overall incidence of drug-related sexual adverse events—including decreased libido, ejaculation disorder, and erectile dysfunction—was slightly, but significantly, greater in the finasteride group than the placebo group (typically 3.8% versus 2.1%). Crucially, the incidence of these new side effects did not increase after the first year of treatment, and many resolved in patients who continued the therapy.
4. Resolving the Risk: Reversibility Data
For most men who do experience sexual side effects, these issues are temporary and reversible. In the initial large-scale studies, virtually all sexual adverse events resolved upon discontinuation of the therapy.
- The Continuation Factor: Notably, approximately 12% of finasteride users who reported drug-related sexual side effects found that these symptoms spontaneously resolved even while they continued taking the drug. This observation underscores the complex, often psychological component of these reported symptoms (the “nocebo” effect).
5. The Controversial Risk: Post-Finasteride Syndrome (PFS)
A significant and serious concern is the existence of Post-Finasteride Syndrome (PFS), a term used to describe the persistent continuation of sexual, physical, and neurological adverse effects despite discontinuing the medication.
- Ongoing Investigation: While the incidence of persistent symptoms is reported to be extremely low in original clinical trials (less than 1%), anecdotal reports and specialized studies suggest a small but real risk. Researchers are actively investigating PFS to better understand the mechanism, risk factors, and true prevalence of these enduring side effects. Patients must be fully informed that while rare, the possibility of persistent symptoms exists.
6. Other Low-Incidence Side Effects
Beyond sexual changes, finasteride carries a low risk of other side effects that patients should be aware of:
- Gynecomastia: A slight increase in breast tissue size is reported in a very small percentage of users (around 0.4% in clinical data), a condition that usually resolves if the drug is stopped.
- Depression/Mood Changes: While not strongly linked in early large-scale trials, more recent case reports suggest that mood changes or depressive symptoms may occur in a small subset of sensitive individuals.
Summary: A High Reward, Low-Prevalence Risk Profile
Finasteride 1mg remains a gold-standard treatment for male pattern baldness due to its ability to significantly stop hair loss progression and promote durable regrowth over many years. The vast majority of men tolerate the drug well, with long-term studies showing high efficacy and a generally safe profile. However, the conversation about finasteride must always be balanced: there is a small, but documented, risk of reversible sexual side effects (affecting around 3-4% of users in trials) and an extremely rare, but serious, risk of persistent symptoms.