The internet is filled with dramatic stories about finasteride side effects. But what do the actual clinical trials—controlled studies with placebo groups—show? The numbers are far less alarming than forum posts suggest.
The Clinical Trial Data
In the pivotal trials that led to FDA approval of finasteride (Propecia) for hair loss:
| Side Effect | Finasteride (1mg) | Placebo | Difference |
|---|---|---|---|
| Decreased libido | 1.8% | 1.3% | +0.5% |
| Erectile dysfunction | 1.3% | 0.7% | +0.6% |
| Ejaculation disorder | 1.2% | 0.7% | +0.5% |
| Any sexual side effect | 3.8% | 2.1% | +1.7% |
Why the Placebo Rate Matters
Notice that the placebo group also reported side effects—2.1% experienced sexual issues on a sugar pill. This happens because:
- Sexual function naturally fluctuates
- Participants are primed to notice issues by informed consent
- Life stressors occur during the trial period
- The nocebo effect operates even in control groups
The only meaningful number is the difference between drug and placebo—about 1.7%.
Long-Term Data: The Rossi Study
A 10-year follow-up study by Rossi et al. (2011) tracked men on finasteride long-term:
- 86% maintained or improved hair status after 10 years
- 2.1% discontinued due to sexual side effects in year 1
- 0.3% discontinued due to sexual side effects in subsequent years
"The majority of men who experience initial side effects either tolerate them, see them resolve with continued use, or discontinue within the first year. Long-term, the dropout rate is extremely low."
Internet vs. Reality
Why do online reports seem so much worse than clinical data?
- Selection bias: Men doing fine don't post; men struggling do
- Nocebo amplification: Modern users are pre-loaded with fear
- Attribution error: All problems get blamed on the drug
- Community effects: Forums create identity around suffering
Clinical trials are controlled, blinded, and include everyone—not just the vocal minority with complaints.
Resolution Upon Stopping
In clinical trials, among the small percentage who experienced side effects:
- Most resolved within days to weeks of stopping
- Some resolved while continuing treatment (suggesting nocebo or adjustment)
- Persistent issues beyond stopping were rare
Putting Risk in Perspective
Compare the finasteride risk to other accepted medications:
| Medication | Side Effect | Rate |
|---|---|---|
| SSRIs (antidepressants) | Sexual dysfunction | 30-60% |
| Beta blockers | ED | ~15% |
| Statins | Muscle pain | 5-10% |
| Finasteride | Sexual side effects | ~2% above placebo |
Finasteride's side effect profile is remarkably mild compared to many commonly prescribed medications.
Make a Data-Driven Decision
Let the evidence guide your choice, not internet horror stories.
Explore OptionsThe Bottom Line
Clinical trial data shows that about 2% of men experience sexual side effects beyond what the placebo group experiences. For most, these resolve upon stopping or with continued use. The catastrophic narratives online are not representative of the typical experience.
References
- FDA Propecia (finasteride) prescribing information and clinical trial data.
- Rossi, A. et al. "Long-term finasteride treatment in male pattern baldness." Journal of the American Academy of Dermatology, 2011.
- Comparative side effect rates from drug labeling databases.