Finasteride is an FDA-approved oral and topical medication commonly used to treat androgenetic alopecia, also known as male pattern baldness. Marketed under brand names such as Propecia (1 mg dose for hair loss) and Proscar (5 mg dose for benign prostatic hyperplasia), finasteride works by inhibiting type II 5-alpha reductase. This enzyme converts testosterone into dihydrotestosterone (DHT), a hormone linked to follicular miniaturization and hair loss.
By reducing DHT levels in the scalp, finasteride helps to slow hair loss, increase hair count, and improve hair density in men genetically predisposed to baldness.
Common Side Effects of Finasteride
Sexual Side Effects
Sexual side effects are the most discussed and studied adverse events associated with finasteride use. In controlled trials of finasteride 1 mg for hair loss, ~1.8% of men reported decreased libido, with ~3.8% reporting at least one sexual side effect (versus ~2.1% in placebo)1,2,3. They typically include:
-
Reduced libido
-
Erectile dysfunction (ED)
-
Decreased ejaculate volume
These effects are generally reversible upon discontinuation, but in rare cases, they may persist.
Other Reported Side Effects
-
Gynecomastia (breast tenderness or enlargement)
-
Skin rash, dizziness, headache
-
Mood changes or depressive symptoms (less commonly reported)
While mood-related effects have been documented, the incidence remains low, and causality has not been firmly established.
Long-Term Use: What Happens Over Time?
Persistence and Reversibility
Most side effects resolve within weeks to months after stopping the drug. However, a subset of users reports persistent symptoms, which has prompted further study.
Fertility Concerns
Finasteride may affect semen parameters, including volume and sperm concentration. These changes are typically mild and reversible, but caution is advised in men actively trying to conceive.
Long-Term Safety Data
Multiple long-term studies, including five-year follow-ups, support the safety profile of finasteride, with no evidence of increased cancer risk at the 1 mg dose.
What Is Post-Finasteride Syndrome (PFS)?
PFS is a term used to describe lingering sexual, neurological, and physical symptoms that persist after discontinuation of finasteride. Symptoms may include:
-
Persistent ED
-
Loss of libido
-
Fatigue
-
Anxiety and depression
Current medical stance: PFS is not officially recognized by major regulatory bodies such as the FDA or EMA, though research is ongoing. Clinicians are encouraged to assess symptoms seriously but emphasize that most users do not experience long-term effects.
How Long Until Finasteride Starts Working?
Finasteride Hair Regrowth Timeline
-
Month 1–2: No visible changes; shedding may temporarily increase
-
Month 3–6: Hair loss stabilizes; regrowth may begin
-
Month 6–12: Noticeable improvements in hair density and coverage
-
Month 12+: Full effect typically evaluated after one year
Patients should give the medication at least 6–12 months before assessing effectiveness.
Topical vs Oral Finasteride: Is There a Difference in Side Effects?
Emerging studies suggest that topical finasteride (e.g., compounded 0.25–0.5% solutions) may reduce systemic DHT absorption, potentially lowering the risk of sexual side effects.
A major clinical trial published in the Journal of the American Academy of Dermatology studied 458 men using either:
-
Topical finasteride (0.25%) once daily
-
Oral finasteride (1 mg) once daily
After 6 months, the results showed:
| Topical Finasteride | Oral Finasteride | |
|---|---|---|
| Hair Regrowth | ✅ Yes | ✅ Yes |
| Scalp DHT Reduction | ✅ Yes | ✅ Yes |
| Blood DHT Reduction | ⬇️ Minimal | ⬇️ Significant (~65%) |
| Sexual Side Effects | 1.3% | 2.1% |
| Discontinuations | None | Rare |
Dutasteride vs Finasteride: Which Is Better for Hair Loss?
What Is Dutasteride?
Dutasteride (Avodart) inhibits both type I and type II 5-alpha reductase enzymes, resulting in greater DHT suppression (~90% vs. ~70% for finasteride).
Studies suggest dutasteride is more effective in promoting hair regrowth and halting progression than finasteride, particularly in men with more advanced hair loss. A 2014 study showed that dutasteride 0.5 mg/day was significantly superior to finasteride 1 mg/day in increasing hair counts at 24 weeks.
When it comes to side effects:
-
Higher potency = potentially higher risk of sexual side effects with dutasteride.
- Due to longer half-life of dutasteride (4-5 weeks), persistent AEs may take longer to resolve.
- Some users report longer-lasting side effects than with finasteride
Should You Take Finasteride? Weighing Risks and Benefits
Finasteride is a clinically validated, first-line treatment for male pattern hair loss. It is best suited for:
-
Men aged 18–41 in early stages of androgenetic alopecia
-
Patients comfortable with the small but real risk of sexual side effects
-
Those seeking a non-surgical solution with solid long-term data
A discussion with a qualified provider, like the professionals at Flycatcher, is essential to determine if it fits your goals and risk tolerance.
Frequently Asked Questions
Q: How common is low libido with finasteride?
A: Clinical trials report ~1.8% to 3.8%, though real-world incidence may vary.
Q: Can finasteride side effects go away after stopping?
A: In most cases, yes. Some individuals may experience lingering symptoms.
Q: What’s the difference between finasteride and dutasteride?
A: Dutasteride blocks more DHT but may carry a higher risk of side effects. Finasteride has more long-term safety data for hair loss.
Q: Is topical finasteride safer than oral?
A: Early data suggests reduced systemic side effects, but more studies are needed.
Q: What is Post-Finasteride Syndrome?
A: A term for persistent symptoms after stopping finasteride. It remains controversial and under investigation.
Final Thoughts: What You Should Know Before Starting Finasteride
Finasteride remains a cornerstone treatment for male pattern hair loss, offering meaningful benefits for many men. Like any medical therapy, it comes with trade-offs. Understanding the risks, monitoring for side effects, and consulting with a provider are key to safe and effective use.
For men looking for a comprehensive, physician-directed approach, programs like GetHairMD from Flycatcher integrate finasteride with non-invasive technologies like laser therapy and follicular infusion for synergistic results.
At Flycatcher Men’s Aesthetics, we’ll help you make the most informed decision for your hair and your long-term confidence.
Conveniently located in Spicewood, just west of the Galleria in Bee Cave, we proudly serve Lakeway, Bee Cave, and the greater Austin area. Call or text (737) 239-0112 today to schedule a no-obligation consultation, including hair analysis and genomic testing.
Early action means better results—don’t wait until it’s too late.
Citations:
1. Adverse Sexual Effects of Treatment with Finasteride or Dutasteride for Male Androgenetic Alopecia: A Systematic Review and Meta-analysis from ActaDV, 2018
2. Persistent Sexual Side Effects of Finasteride for Male Pattern Hair Loss from The Journal of Sexual Medicine, Volume 8, Issue 6, June 2011, Pages 1747-1753
3. Abstracts from the current global literature: Finasteride and sexual dysfunction from Indian Journal of Sexually Transmitted Diseases, 2017
