They stopped taking finasteride, but the side effects didn’t stop.
- Sex, sleep, mood, masculinity - destroyed by a pill for hair loss.
- Thousands affected worldwide. Men and women.
- Known on paper, not in practice. No code, no treatment.
Finasteride blocks an enzyme that makes at least 5 hormones, not just DHT.Traish, Endocrine Practice 2012
Only 1-10% of drug reactions get reported. So every number here is too low.FDA FAERS
About 7 million US prescriptions a year. 1% is tens of thousands of people.FDA prescription data
Still no ICD code, 15 years after the label changed. So nobody counts PFS.ICD
What PFS is
PFS (Post-Finasteride Syndrome) is when finasteride side effects do not go away after you stop taking it. Sex, body and thinking can all be hit. For some people it never stops.
Finasteride blocks an enzyme called 5-alpha reductase. That enzyme turns testosterone into DHT, and blocking it slows hair loss. The same enzyme also makes brain hormones for mood, memory, sex and sleep.
Roberto Melcangi's team in Milan found the drug changes how genes switch on and off (epigenetic changes). This may be why symptoms carry on after the drug has left the body.
Symptoms of PFS
PFS hits sex, the brain and the body. Symptoms can start while you take the drug, or after you stop.
Sex
5- No sex drive at all
- Erectile dysfunction (no erections)
- Weak orgasms, or no pleasure
- Numb genitals
- Less semen
Brain and mood
5- Bad brain fog
- Memory problems
- Cannot sleep
- Emotional numbness (you feel nothing)
- Depersonalisation (you feel unreal)
Body
5- Always tired
- Muscle loss
- Joint pain
- Thin skin
- Gynecomastia (breast growth)
This list is not complete. It shows the symptoms patients report most often.
PFS by the numbers
These numbers are too low. The FDA says only 1-10% of drug side effects get reported. Academic studies say it is even lower.
So the 11,557 FAERS reports are a fraction of the people affected. Reports are also split across countries and code systems. One patient can end up under three codes, so no database sees the pattern.
Nobody knows the true number yet.
What regulators have done
Proscar approved (5mg)
The FDA approves finasteride for enlarged prostate. The label says side effects go away.
Propecia approved (1mg)
A lower dose is approved for male hair loss. The label says nothing about lasting effects.
FDA warns the effects may last
The label now says sexual side effects "may persist after discontinuation". That means they can last after you stop.
FDA adds suicidal thoughts to the label
It is listed as a side effect, not a warning. Patients had asked for this in a petition. The FDA said the evidence does not prove finasteride causes it.
MHRA strengthens UK warnings
The UK adds patient alert cards for sexual problems, depression and suicidal thoughts. Doctors are reminded that sexual effects can last after stopping.
EMA confirms suicidal thoughts as a side effect
An EU review confirmed suicidal thoughts as a side effect of finasteride 1 mg and 5 mg. Packs of 1 mg must now carry a card about mood changes. The EMA still says the benefits are greater than the risks for approved uses.
Key research
Independent researchers are working out how PFS happens. Merck is not known to fund any of it.
Melcangi et al. (2013-2024)
Milan studies found changed levels of brain hormones (neurosteroids) in spinal fluid, blood and stool.
Csoka & Szyf (2009)
Drugs like finasteride can change how genes switch on and off (DNA methylation), long after the drug is gone.
Khera et al. (2014)
PFS patients had too many androgen receptors (testosterone docking points) in penis tissue, a failed fix by the body.
Melcangi et al. (2021)
PFS patients had big changes in their gut bacteria, which may be linked to brain symptoms.
What doctors say, and what the evidence shows
Most doctors follow guidance that has not caught up. The problem is the information, not the doctor.
What doctors say
"Side effects are rare, and they go away."
What evidence shows
In 2011 the FDA made the label say sexual side effects may last after you stop. A 2017 study found lasting erectile problems in 1.4% of young men (median 205 days of use).
What doctors say
"It only happens to a few people."
What evidence shows
With 7 million+ US prescriptions a year, even 1% means tens of thousands of new cases. Only 1-10% get reported, so the true total may be 10 to 100 times the WHO VigiBase count.
What doctors say
"Nobody has proved how the effects could last."
What evidence shows
Peer-reviewed studies found gene changes, brain hormone changes, androgen receptor changes and gut bacteria changes in PFS patients. Merck has not publicly funded any of it.
What doctors say
"It does not affect mental health."
What evidence shows
In 2022 the FDA added suicidal thoughts and behaviour to the label, as a side effect, not a warning. It said the evidence does not prove finasteride causes it. Depression, anxiety, brain fog and emotional numbness are among the most reported lasting symptoms.
What treatment exists today
An honest look at what exists, and what does not.
Important: There is no FDA-approved treatment for PFS. No drug company has funded treatment research. Everything below comes from independent research and from patients.
The Milano Project is the most advanced work
Roberto Melcangi's team in Milan is studying allopregnanolone, a brain hormone that runs low in PFS patients. In animals, giving it back reversed some changes finasteride had caused. Patient donations fund the whole Milano Project.
What some patients report
No treatment is proven. Some patients say these things help a little. These are reports from patients, not advice.
- Regular exercise, especially weight training
- Better sleep and less stress
- Diet changes, such as anti-inflammatory food
- Time. Some report slow, partial improvement over months or years
Caution: Be very careful with unproven treatments sold online. Some can make symptoms worse. Always talk to a doctor before you try anything, and use our Support Library for checked resources.
How to get help
You do not have to face this alone. Here is where to start.
WhatsApp support groups
Private, moderated groups with other PFS patients. Talk to people who understand.
Join the patient registry
Add your case to the SIDEfxHUB registry. Your anonymous data helps researchers work toward treatment.
Report your side effects
Report to your national regulator (FDA, MHRA, EMA). Few reports make the drug look safer than it is.
Support library
Research papers, patient stories, news and practical help, all in one place.
Hear from PFS patients
Real patients talk about living with PFS.
Mark's Story
Mark has lived with finasteride side effects for over 2 years.
Sam's Story
One pill destroyed Sam's life. Sam talks about the finasteride side effects.
20 Years of PFS
A patient who has had PFS for over 20 years tells the story.
Sources & databases
Every number on this page comes from these sources.
FDA FAERS
The FDA Adverse Event Reporting System, the main US database for drug safety reports.
Visit database →WHO VigiBase
The WHO global database, with over 30 million safety reports on file.
Visit database →PubMed PFS research
Search published PFS research on the NIH database.
Search PubMed →PFS Foundation
The main organisation funding PFS research, including the Milano Project.
Visit website →EMA finasteride review
The European Medicines Agency's safety review of finasteride products.
View review →RxISK
Independent drug safety group. Report side effects and read the data.
Visit website →I think I have PFS. What now?
If you recognise these symptoms, here are 5 steps you can take right now.
Connect with others
Join a WhatsApp support group. Talk to people who know what this is like.
Report your side effects
Report to your country's health regulator. Every report makes these conditions harder to ignore.
Read about managing symptoms
Our Support Library has guides on coping, talking to your doctor and daily life.
Join the registry
Register your experience anonymously. Your data helps research and shows the real scale.
Think you have PFS?
You are not alone. Join the registry, meet other patients, and help push the research forward.