Health

Hair loss drug finasteride can cause debilitating side-effects, men say

For decades, millions of men around the world have turned to a drug — finasteride, or Propecia, its most well-known brand name — to slow hair loss. But an increasing number of experts are sounding the alarm that this medication can cause rare but serious side-effects, which can persist after stopping treatment.

Pharmaceutical company maintains the medication is safe

A person holds their hands to the top of their head, which shows some hair loss.
Men interviewed by CBC/Radio Canada during a six-month investigation of the hair loss drug finasteride say it caused sexual, psychological and physical side-effects for them that have lasted months if not years after they ceased taking it.  (cunaplus/Shutterstock)

WARNING: This story contains discussion of suicide. 

Marc Turner's mother remembers him coming home with a prescription in the fall of 2020.

"He was really excited to take it. I can literally remember him running in the house," said Denise Turner. "He was like: 'I know it's a lifelong drug, but it's going to work.'"

The 35-year-old living in Mississauga, Ont., had been concerned about losing his hair. The medication, a popular drug called finasteride, promised to curb the issue. His doctor warned him side-effects — erectile dysfunction and a lowered libido — were possible, but the doctor told Marc these symptoms would cease if he stopped the medication. 

Marc's excitement was short-lived. 

"Three weeks after starting, he said to me: 'I'm having some funny feelings in my head, like brain fog or something,'" his mother said. 

When Marc lowered his dose, the side-effects got worse. After a few months, he quit completely. 

A person sits on a couch with a dog beside them. A picture of a person is on a table behind them.
Denise Turner sits by a photo of her son, Marc Turner, who suffered from side-effects of finasteride. (Brigitte Noël/CBC)

Denise Turner said that's when the family's nightmare truly began. Over the next few months, her once-healthy son's condition worsened. The loss of his sexual functions continued and he experienced fatigue, anxiety, tinnitus and a plethora of physical symptoms. 

Finasteride — or Propecia, its most popular brand name — was invented by Merck. The pharmaceutical company insists that it's rare for men on the medication to experience side-effects, and has long maintained they vanish once the medication is stopped. 

But 25 people interviewed by CBC/Radio Canada during a six-month investigation of finasteride's side-effects tell a different story. They say the drug caused sexual, psychological and physical side-effects for them that have lasted months if not years after they ceased taking the drug. 

WATCH | Are the risks of Finasteride being downplayed?:

A popular hair loss drug and its lesser-known, rare and potentially life-altering side effects

16 hours ago
Duration 5:17
[Warning This story contains discussion of suicide] For decades, millions of men have taken the prescription drug finasteride, often known by the brand name Propecia, to slow hair loss. But a Radio-Canada investigation breaks down the expert warnings about rare but life-altering side effects that persist after treatment stops — and allegations that drug developer Merck has downplayed the risks.

'These men were not recovering'

Denise Turner said the worst of her son's symptoms was anhedonia, the inability to feel emotions.

"I used to fight with him. I'd say: 'What do you mean you don't feel love, Marc?' He'd say, 'I can't feel it anymore, mom. There's no comfort anywhere.'"

She said the medical community was at a loss.

"His doctor was saying: 'There's no way Marc, this drug would not do that, you're off the drug. There should be no problems.'" 

Two men stand in a room.
Marc Turner, left, shown at his sister’s wedding in 2017, found references online to thousands of other men sharing the same symptoms he had, ailments they all attributed to finasteride. (Young Glass Photography)

Online, however, Marc found thousands of other men sharing the same symptoms, ailments they all attributed to finasteride. 

"It was very validating, but scaring him silly," said Denise Turner. "These men were not recovering."

Mysterious symptoms

The men interviewed by CBC/Radio-Canada said their symptoms are debilitating: loss of libido, erectile dysfunction, infertility, cognitive and physical issues, anxiety, insomnia, depression and, in many cases, suicidal ideation. 

"It's a complete chemical castration where you have no chemical reaction to anything sexual, anything in life," said Michael, a British Columbia man who says his symptoms have lasted more than 15 years. 

"You are suddenly living in black and white while everyone else is still in colour."

Like several other men quoted in this story, he asked that his identity be protected because he fears the impact on his personal and professional life.

A person with their back to the camera speaks to another person.
Many of the men who spoke to CBC/Radio-Canada about their symptoms asked that their identity be protected. (Jean-Philippe Pelletier/Radio-Canada)

Some of the men say the medication has cost them their relationship, their family and their career. Some cases were reported to us by the families of men who took their own lives. 

This rare condition is often referred to as post-finasteride syndrome, or PFS, a pathology attributed to men who still experience the drug's side-effects more than five months after cessation. 

While this syndrome is gaining traction in some spheres of the research community, patients say it remains relatively unknown or is considered controversial among medical professionals. And even though several of finasteride's side-effects are now clearly listed in the product monograph, affected men say their doctors did not adequately communicate possible risks.

Experts say the medical community's lack of knowledge about finasteride's risk appears to be by design. 

Merck — the multinational that made billions of dollars from Propecia — has been accused of producing misleading safety data, funding unreliable studies and running predatory marketing campaigns. And the company's own internal documents suggest the company was aware of some of the serious risks linked to its drug from the beginning.

Intended to treat prostate issues

Finasteride was invented in the 1990s by pharmaceutical multinational Merck. A first version, called Proscar, was intended to treat enlarged prostates, but had the unintended side-effect of prompting hair growth. As such, in 1997, a smaller dose called Propecia was patented to treat hair loss. 

Finasteride "blocks the conversion of several hormones and neuro steroids in the brain," said Michael Irwig, an endocrinologist and professor at Harvard University in Boston who has studied the drug and its impacts.

"That has implications for how nerves communicate to each other, and I hypothesize that it can impair libido and erectile function."

Dr. Serge Carrier, a Montreal-based urologist who has seen PFS patients, said such serious side-effects remain rare. 

"It's important to remember that the majority of patients will not experience permanent symptoms with this type of medication," he said. "The problem is that we don't know which men could develop these symptoms or why."

A person sits in a chair in front of a window.
Dr. Serge Carrier, a Montreal-based urologist who has seen post-finasteride syndrome patients, says serious side-effects from finasteride remain rare. (Jean-Pierre Gandin/Radio-Canada)

Another issue, according to Irwig, is that these risks are not adequately communicated to the public. 

"The truth is that we really don't have good data about the incidence of the persistent sexual side-effects," he said, adding the clinical trials "didn't have a lot of people in them and were not long-term."

Around the world, several hundred men have launched lawsuits against Merck. 

They claim Merck failed to warn them about the product's persistent side-effects. Cases in Canada, Germany, Israel and France are ongoing, but others have been settled. 

In the U.S., more than 1,100 individual lawsuits were consolidated and taken to Federal Court: this case was settled out of court in 2018, for $4.3 million US.

In 2019, evidence from this case became public, in a Reuters investigation that exposed some of the company's internal emails.

Safety data said to be 'misleading' 

Since its launch, Propecia's product monograph has mentioned the risk of side-effects such as decreased libido, erectile dysfunction and ejaculation disorder, but states that "the incidence of each of the above side-effects decreased to ≤0.3 per cent by the fifth year of treatment." 

In these internal exchanges, however, a Merck scientist calls this safety data "misleading." He points out that to achieve such a low number, his colleagues had excluded all men who had left the studies because of sexual side-effects. 

While the company has long claimed that side-effects disappear when users stop the drug, other internal emails suggest some of the clinical trial participants did have persistent adverse effects after cessation. 

"Nothing has been reported about these men who developed these persistent side-effects. So we don't know if they ever recovered or not," said Irwig.

A person sits in an office with a plant and photographs in the background.
Harvard University Prof. Michael Irwig says finasteride’s risks are underestimated. (Radio-Canada)

In court documents, Merck is alleged to have hidden this information from the public. The risk of persistent sexual side-effects was only added to the product's monograph years after the product was put to market, at health regulators' requests. And while several European countries forced the change in 2008, Health Canada only acted in late 2011.

Merck did not agree to an interview with CBC, but told Reuters those internal emails were taken out of context. 

The Propecia brand is now the property of pharmaceutical company Organon, a Merck spinoff, which told us they maintain the medication is safe.

Stigmatizing baldness

The CBC/Radio-Canada investigation found that Merck invested heavily in the stigmatization of baldness through mainstream advertising campaigns, but also through more covert means. 

In the early 2000s, several news articles were published about the distress caused by hair loss in men. These stories all bore similar hallmarks: a hair research institute presenting the results of surveys showing that bald men had fewer job opportunities and less luck in love than their well-coiffed counterparts, and dermatologists who revealed the existence of medical solutions.

However, our reporters found that this research institute, the surveys and dermatologists all received funds from the pharmaceutical company. 

An advertisement in a journal regarding a drug for male hair loss.
Propecia is promoted in an advertisement published in the Journal of the American Academy of Dermatology in November 1998. (Submitted by name withheld)

Merck also paid researchers to give presentations on the anxiety caused by baldness at medical conferences — and sometimes even at hair stylist conferences — around the world.

Marc-André Gagnon, a pharmaceutical policy expert at Carleton University in Ottawa, says pharmaceutical companies' marketing campaigns often go well beyond conventional advertising. 

"You don't create a commercial success without hiring a public relations firm to organize the narrative [around the drug]."

Looking for information

Many affected men who spoke to Radio-Canada say that before taking the drug, they consulted informational videos and research papers that concluded finasteride was safe.

"Most of the sources I consulted never mentioned the possibility of persistent side-effects," said Wei Wong, a 29-year-old Montrealer who began experiencing symptoms after about 10 days of using topical finasteride. 

In a blog post, Marc Turner wrote that he was convinced by a paper that post-finasteride syndrome was a delusional disorder brought on by mass hysteria. "My thought was that if PFS does exist, then it is extremely rare."

A person stands outside with a city streetscape behind them.
Wei Wong began experiencing symptoms after about 10 days of using topical finasteride. (Michel Riverin/Radio-Canada)

However, in 2015, American researchers analyzed 34 finasteride clinical trials and concluded that more than half were funded by pharmaceutical companies — 16 by Merck — and that the available toxicity information was "systematically biased" and of "poor quality."

Other men say they were influenced by the heavy handed and omnipresent ads for telehealth websites devoted to men's health. 

"It's everywhere, every time I scroll on Instagram I get targeted by this," said John, a 32-year-old Ontario man whose symptoms have been ongoing for four years. "There are so many ads pushing this to young men."

More prescriptions being filled

Propecia's patent expired in 2013. With the arrival of generic finasteride, several other new players have begun selling the drug.

Our reporting revealed that many telemedicine sites focused on men's health offer little information about their products' risks. Some users believe they might even profit from the side-effects. 

"They are winning on all fronts because they sell two things: hair medications and erectile dysfunction medications," said Sam, a 40-year-old Quebec man who says he has been suffering from post-finasteride syndrome for a year and a half. 

"Your hair medication caused erectile dysfunction? No problem, we've got another pill for you."

Health Canada's website reports that in 2014, approximately 1.2 million finasteride prescriptions were issued in the country. By 2023, that number had increased by nearly 50 per cent, reaching close to 1.8 million prescriptions, according to data provided by health data company IQVIA.

This uptick should worry regulators, said Julien, a 38-year-old Montrealer who has been struggling with PFS for nearly a decade. 

"It's just statistical. You may only have a minority of people who have the syndrome, but if tomorrow 25 per cent of the population is taking finasteride, we'll have a real problem."

Need for more research

Marc Turner never recovered. In April 2022, a year and a half after his first dose of finasteride, he took his life. Online, he left a diary of his struggles and a message of warning to other men. 

"There have been too many people's lives destroyed, families devastated and suicides because of a drug for a cosmetic purpose," he wrote. "This cannot be tolerated any longer."

Denise Turner hopes telling her son's story will help raise awareness. 

"Marc really, really wanted to get this out there," she said. "There needs to be more information, [doctors should] delve into the patient's history a little more and tell men exactly what the warnings are."

A closeup of a man's balding head with a hand held to the forehead.
Propecia is designed to treat male pattern baldness, a common form of baldness where the hair recedes on either side of the head. (Ian Waldie/Reuters)

Overseas, warnings about finasteride's risks are becoming more strident. 

In 2023, following a rise in reports of serious adverse effects linked to finasteride, the U.K. health regulator launched an awareness campaign about finasteride's potential side-effects and added new warnings to the drug. 

The European Medicines Agency is conducting a similar review of medications containing finasteride or dutasteride, which could alter the guidelines governing prescription of these drugs in Europe.

Health Canada says it is keeping an eye on these conversations. 

Around the world, a handful of researchers have been working to find the cause — and a cure — for post-finasteride syndrome. Their work is often funded by affected patients' donations.

Hockey players skate on ice.
Marc Turner's friends, wearing his jersey number, take part in their annual post-finasteride syndrome fundraising hockey game. (Samantha Carcaole)

In Mississauga, Marc Turner's friends have been organizing an annual hockey tournament in his honour to raise money.

"It's pretty crazy to think that we have to try to raise bits and pieces, to get even one study, one small study out," Denise Turner said. "But it is hopeful. It's much more hopeful right now than it has been in two years' time."


If you or someone you know is struggling, here's where to look for help:

ABOUT THE AUTHOR

Brigitte Noël

Journalist

Brigitte Noël is a journalist with the investigative program Enquête at Radio-Canada.

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