A bibliography on adverse effects of finasteride

I’ve been meaning to do this for a while. I’ve compiled a bibliography of 185 papers relevant to finasteride and adverse effects:

:man_scientist: Finasteride bibliography :woman_scientist:

I am aware of a few others I need to add.


Amazing job! Thank you!

This one is new. This author has written a lot about this although not always in the context of finasteride but in the context of the role of 5a-reductase.

The most recent meta-study that was published, in the Journal of American Academic Dermatology (J Am Acad Dermatol), suggested that the evidence was balanced in favor of post finasteride syndrome existing. I think this was particularly notable as it was the same journal in which the original Propecia or finasteride studies were published. Suggests that medical consensus is moving towards accepting PFS.

Fascinating paper. I just added it to the bibliography and sent the bibliography link to Valerie Langlois in Canada. How did you find out about this one? PubMed alerts?

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@Frustrated Post Finasteride Syndrome has not been validated as a medical term, although there is now a pretty extensive history of papers documenting adverse sexual effects of finasteride.

Regarding the “original finasteride study”, maybe that’s this one in the New England Journal of Medicine?

Gormley GJ, Stoner E, Bruskewitz RC, et al. The effect of finasteride in men with benign prostatic hyperplasia. The Finasteride Study Group. N Engl J Med. 1992;327(17):1185-1191. doi:10.1056/NEJM199210223271701

That was way back in 1992, and six of the co-authors were from Merck Research Labs. This is in the Results section:

The frequency of adverse effects in the three groups was similar, except for a higher incidence of decreased libido, impotence, and ejaculatory disorders in the finasteride-treated groups.

What does that mean? I am actually curious. What needs to happen for PFS to be considered “real”? Does there need to be a vote about it? And who needs to vote?

I found the paper because I impulsively search the web for finasteride and PFS every couple of hours. Not even using alerts…

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@Sibelio That is a great question. I have reached out to some researchers to get their take. Here are some considerations:

  • There is no ICD code for Post-Finasteride Syndrome.
  • The syndrome is described and advocated by the PFS Foundation, which is not a medical organization.
  • There is a long history of findings of adverse sexual side effects while taking finasteride and after stopping. The research has picked up pace in recent years. However there are not a lot of large-scale, high-quality studies out there. Moreover, the large studies have not looked at a “syndrome”; they have looked at specific side effects.
  • The studies that do mention a “syndrome” either put it in quotes, or put it forward as a hypothesis.
  • The syndrome as defined on the PFS Foundation website has many symptoms in the categories of sexual, physical and psychological. I doubt that all of us are experiencing all of those symptoms (I’m not). Some may be common, others less common or rare. What if someone only has depression after taking finasteride, but not the sexual symptoms – is that PFS? What about only gynecomastia – is that PFS? For a syndrome or condition to be valid, it has to have a clear definition and diagnostic criteria.

We have a lot of case reports and some clinical data suggesting there are biochemical, genetic, sexual and psychological changes as a result of taking finasteride. But for it to be accepted as valid, it has to meet criteria of evidence-based medicine.

The sexual and psychological symptoms make this a challenging research topic because it’s somewhat rare, and erectile dysfunction can have other contributing factors. Another challenge is that men are likely to underreport sexual symptoms out of embarrassment or discretion. It looks like the symptoms involve a highly complex metabolic cascade that we do not fully understand.

For a more in-depth discussion, see this article:

I look to people who have other rare diseases such as Lyme Disease and Chronic Fatigue Syndrome (now called ME/CFS). For many years, doctors were skeptical whether these were real, and in the case of ME/CFS, thought it was “in their head” and they just had psychological problems. Both of these diseases are also not understood and highly complex. The good news for these communities is that the CDC, NIH and other medical institutions are now taking both diseases much more seriously. Medicine moves slowly.

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Very interesting paper, thank you!

I actually haven’t read Belknap’s paper on finasteride adverse effect reporting but I should.

Have you read the minutes of the FDA advisory committee that approved finasteride?

Some other things I have wondered a lot. Perhaps you can enlighten me based on your extensive research and general knowledge.

Why hasn’t the FDA or CDC initiated the type of investigation or study that would attempt to ascertain the etiology of the adverse effects or at least prove their existence in an unambiguous manner?

Are these regulatory agencies under no legal obligation to follow up with patient adverse reports?

Why is “safe until unambiguously proven unsafe” the standard for approved drugs and why is the burden of proof for establishing lack of safety on the patients who somehow need to fund a study that nobody wants to run, while the regulators and the manufacturer are happy to extend the period of uncertainty indefinitely?

Does the FDA have the authority to demand additional studies or clinical trials from the sponsoring company to determine safety when sufficient doubt about safety have been raised? And what criteria would the FDA use to determine that sufficient doubt has been raised?

Obviously these are very complex questions about the regulatory environment and unfortunately the actions of the regulators will depend on subjective judgments. However, I would think that the legislator has attempted to regulate these matters more formally, at least in theory?

Finally, when a company deliberately does not measure adverse effects or hides them or falsifies data or clearly misinterprets data for its benefit AND the FDA pretends to be satisfied about a drug’s risk-benefit profile, doesn’t the public have the right to take the FDA to court for failing to uphold the public interest?

Currently, if I can use a metaphor, the wolf is in charge of guarding the sheep. Every night sheep disappear and when the other sheep report that to the night guard, the night guard says they have seen nothing. And that’s that.

The original Propecia study I was talking about was the Propecia Hair Loss Study Group from Merck, published in JAAD in 1998.


It isn’t so important what the scientific community calls PFS, but the term has been used by name in quite a few of the articles you collected. I’m not aware of any scientific bodies that can officially recognize the name of a condition, but the NIH did include PFS in its database of genetic and rare diseases. It wasn’t necessarily an official recognition because that’s not the point of the database, but they did include it.

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Thanks for mentioning this article @Frustrated

It’s missing from the bibliography and it’s an important one. I will add it. Here’s what they reported about adverse events, with the data table attached.

In the first year, a slightly higher proportion of finasteride-treated than placebo-treated patients reported adverse events related to sexual function (4.2% vs 2.2%, P < .05; see Table IV for details). Only 11 men (1.4%) in the finasteride group and 8 (1.0%) in the placebo group discontinued the study because of sexual adverse events, which resolved after discontinuation. These adverse events also resolved in many of the patients who reported them but who remained on the finasteride regimen and continued in the study.

I think they are excluding men who discontinued the study from the overall calculation. (See Belknap 2015 for more about flaws in the clinical trials.)

Another issue which Thomas Moore has pointed out is that surely the people asking men about side effects in the clinical trial would often be women. Men would be embarrassed and shy about reporting side effects, so they are probably underreported. It’s also possible that one year is not long enough, or that side effects after discontinuation were not reported because men had left the study and were not asked. Many problems with this trial.

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@Frustrated you wrote:

It isn’t so important what the scientific community calls PFS, but the term has been used by name in quite a few of the articles you collected.

You’re right, a few articles have used this term. One of them, called “Post Finasteride Syndrome,” puts it this way:

Post-finasteride syndrome is an ill defined and controversial syndrome associated with a constellation of sexual, physical, and psychological symptoms that develop during or after finasteride exposure and persist after discontinuation
Gray & Semla, 2019 https://www.bmj.com/content/366/bmj.l5047

Another paper published last year is called “Post-finasteride syndrome - does it really exist?” The title is revealing – it suggests there are people who are not convinced it exists.
Maksym et al: https://www.ncbi.nlm.nih.gov/pubmed/30651009

Here’s an excerpt which I think is a good balanced take (emphasis added):

The post-Finasteride syndrome (PFS) has been claimed to occur in men who have taken oral finasteride to treat hair loss or benign prostatic hyperplasia. While the incidence of persistent sexual, mental, and physical side effects despite quitting finasteride is unknown, and the condition is not recognized by the scientific community, individuals who suffer from PFS do present with very distinctive and homogenous symptoms. The concept has emerged from reports of nondermatologists, neuroendocrinological research, case reports, and uncontrolled studies. These have been scrutinized by hair experts who found that persistent sexual side effects were only documented in low-quality studies with a strong bias selection and a significant nocebo effect. Others totally dispute the credibility of the PFS. In any case, the PFS is a problem that has to be dealt with.

This one uses the term openly: Than et al, 2019.

It’s not a black and white thing. The good news is that more research is coming out, and the body of evidence is growing. See the bibliography (new URL): https://finasteride.network

We are in a pickle because the side effects are rare, and can take a while to appear, so it’s hard to design and carry out large-scale, high-quality studies.

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Merck’s large-scale clinical trial had a material number of subjects develop sexual problems that did not reverse upon discontinuation of the drug. As you know, this was withheld from the public but was finally reported in the Reuters article. Almost all of the articles were written before the Reuters article was published. That is really enough to prove that PFS exist.

The other large scale epidemiology study was from Dr. Belknap and was published in 2017. It showed about 1% of patients developed persistent sexual problems which is close to Merck’s clincal trial in fact.

It certainly won’t hurt to get more studies and research, but we already have enough to prove this exists. It’s a matter of information diffusion. More people need to be aware that Merck fraudulently withheld the data from the original clinical trials. If you find certain adverse events in clinical trials, people generally don’t deny them because the clinical tests are high powered.

There were other articles that use the term PFS as well that you didn’t mention.


@Frustrated Bodies that recognize diseases include the American Medical Association which manages CPT and WHO, which publishes ICD (used outside the US, but AMA and WHO try to stay in sync). I think relevant medical specialty boards are also involved, such as the American Academy of Dermatology.

To pick one example, here’s a press release reporting that AMA recently voted to designate infertility as a disease: https://www.ama-assn.org/delivering-care/public-health/ama-backs-global-health-experts-calling-infertility-disease
In 2013 AMA voted to designate obesity a disease: https://obesitymedicine.org/why-is-obesity-a-disease/

Once a board and the AMA designate something a disease, then diagnosis and treatment are specified, it’s added to the coding system(s) such as CPT, insurance companies have to consider covering it and doctors have to be trained in it. It’s not a perfect system, but it is how the system works.

NIH GARD’s page is titled “Adverse events of 5-alpha-reductase inhibitors”. They explicitly avoid any backing of the term PFS. The first paragraph opens with: “This page does not serve as an official recognition of post-finasteride syndrome by the NIH.”

The page is titled adverse events of 5-alpha reductase inhibitors because the syndrome can also be caused by Saw Palmetto and Dutasteride so PFS is overly specific. But they do use PFS under other names just below it. The disclaimer wasn’t there until they added it after it caused a controversy and one of the Wikipedia editors, likely involved with Merck, reached out and pressured them a little.

The AMA sent out a newsletter with one of the PFS articles many years ago, I think in 2013, but I don’t remember which article. My friend forwarded it to me.

@Sibelio Why hasn’t the FDA or CDC initiated a major investigation or study of adverse effects? This gets to the whole drug regulatory framework in the US, a complicated topic that I don’t know much about. FDA takes side effect reports at MedWatch and presumably monitors them. It maintains a page at GARD.

Today I learned that in 2017, PFS Foundation submitted a Citizen Petition to take finasteride (1mg) and Propecia off the market:

On March 15, 2018, FDA replied: “FDA has been unable to reach a decision on your petition because it raises complex issues requiring extensive review and analysis by Agency officials. This interim response is provided in accordance with FDA regulations on citizen petitions (21 CFR 10.30(e)(2)). We will respond to your petition as soon as soon as we have reached a decision on your request.”

I don’t see any more recent communications since then.

Are these regulatory agencies under no legal obligation to follow up with patient adverse reports?

I don’t know what the legal and regulatory obligations are.

…why is the burden of proof for establishing lack of safety on the patients who somehow need to fund a study that nobody wants to run, while the regulators and the manufacturer are happy to extend the period of uncertainty indefinitely?

It’s crazy and wrong. The pharma-regulatory-medical complex got us into this horrible mess (Merck, FDA, doctors), and they should help get us out. There are some good, even heroic, researchers out there who are making progress. We can also organize to help support the research and move it forward.

Does the FDA have the authority to demand additional studies or clinical trials from the sponsoring company to determine safety when sufficient doubt about safety have been raised? And what criteria would the FDA use to determine that sufficient doubt has been raised?

So far FDA (as well as other governments) are sticking to the language of “patients have reported X, Y and Z effects.” They required Merck to add reports of persistent sexual side effects to the patient information label in 2013.

I’d like to know the status of the Citizen Petition from PFS Foundation. It forces FDA to take a position rather than being passive.

…doesn’t the public have the right to take the FDA to court for failing to uphold the public interest?

I’m curious about this, but I don’t know.

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A lot of what you say makes sense in a fair and just world, but none of what happened to us is fair and we aren’t going to further ourselves due to the goodness of a just world.

To start to make progress for the PFS community, you have to primarily think about what what most likely will have an impact versus what should have an impact. Find the right levers and techniques to pull that will effect change.

The Citizen Petition presented evidence to the FDA where THE Merck regulatory exec for Propecia admitted to withholding information from the public on the warning label. That SHOULD have been enough but to date they haven’t done anything. It will be important to find the right way to go about it and that’s still a work in progress. It’s unfortunately going to be the case with pretty much any kind of change we want to implement because we are in a group that society just doesn’t care about for several reasons.