(SOUNDBITE) (English) KELLY PFAFF, A PLAINTIFF SUING MERCK, SAYING:

"This was him back in the early days of surfing, when I first met him. And then this is the very last picture I took of him, because when he was struggling, and I was trying everything, like,didn't know what else do to, like, 'go surfing, you love surfing. You never surf. Go surf.' And he did go surfing his last time. But he didn't look totally happy there. Every time I took a picture of him, even in this one. I feel like I can see right throughhis soul. Like he's not there. He's gone. But he's trying so hard to pretend like he's there. That's why this drug is awful because it's so confusing."

Kelly Pfaff's husband John was in his 30's when started taking the commonly prescribed drug Finasteride, under the brand name Propecia to treat hair loss.

After he started taking Propecia, his wife Kelly says his mood darkened.

He lost interest in sex. He gained weight. He suffered insomnia.

(SOUNDBITE) (English) KELLY PFAFF, A PLAINTIFF SUING MERCK, SAYING:

"Just to show you how mild his balding was, this is him playing Twister. And his bald spot is very minimal. But it was enough to bother him. And it was enough for him to take this drug. So,there he is playing with the kids."

John eventually quit the drug, but his depression deepened even after he stopped taking it.

In 2013, John killed himself.

And in 2015, Kelly Pfaff sued Merck, the maker of Propecia.

She claims that Merck knew that the drug could cause the persistent sexual dysfunction and depression that led to her husband's suicide.

Her lawsuit is one of over 1,100 that accused Merck of not adequately warning patients of Propecia's potential sexual side effects.

(SOUNDBITE) (English) KELLY PFAFF, A PLAINTIFF SUING MERCK, SAYING:

"It didn't need to happen. It did not need to happen, and it's still happening."

Merck told Reuters that it stands by the safety and efficacy of Propecia, and points out that it has been prescribed safely millions of times.

The pill has some prominent users.

(SOUNDBITE) (English) WHITE HOUSE PHYSICIAN RONNY JACKSON, SAYING:

"He takes Propecia 1 mg daily for prevention of the male pattern hair loss."

If you look at the drug's information packet, you'll see that it warns that a very small percentage of men can experience decreased libido, erectile dysfunction and other sexual problems as possible side-effects.

At the same time, the company has for years rejected allegations that Propecia causes effects that persist after men stop taking it, or that it causes depression.

It also says such symptoms could be caused by a variety of other factors.

In a 2017 court filing defending the drug, Merck's lawyers wrote that "sexual dysfunction is very common in men," and added that "premature hair loss itself, the very condition for which Propecia isprescribed, is a associated with low self-esteem, poor body image and depression."

But confidential documents filed by plaintiffs reviewed by Reuters accuse Merck of exaggerating the drug's safety record.

Dan Levine is a legal correspondent for Reuters.

He found a court filing that argues Merck under-reported the number of men who experienced sexual side effects, and misreported the duration of those symptoms.

(SOUNDBITE) (English) REUTERS CORRESPONDENT DAN LEVINE, SAYING:

"So, you can see in the court there's a section head, which says 'Merck recognized evidence of persistent sexual dysfunction long before it modified the Propecia label.' 'Merck uncovers proofof persistent sexual dysfunction, post-use and does nothing to alert consumers or doctors.' Andthen there are several sentences within it that are immediately redacted and that you can't see."

Merck says that Propecia's label has always accurately reflected data from the company's clinical trials.

The plaintiff's lawyers claims were based on their reading of internal Merck documentation, which the company handed over under a court order to keep that information confidential.

Plaintiffs lawyers filed some of what they learned as evidence with the court, redacted.

While the heavy black lines obscured the words, in some cases, the digital text was preserved beneath.

(SOUNDBITE) (English) REUTERS CORRESPONDENT DAN LEVINE, SAYING:

"Control-copy, and then control-v, paste, and then you can read what was underneath here."

Thanks to what might be a lawyer's error, Reuters was able to lift the digital redactions over a small portion of the legal filings.

That narrow crack in the wall of legal secrecy opened a window into what Merck knew about a drug it wanted the world to believe was safe.

The documents refer to test results from a five-year study, where 23 test subjects reported sexual side effects between years three and five.

Nine suffered side effects that eventually went away.

The time it took for the symptoms to stop is unknown.

Seven of them were still suffering symptoms when they completed the study, and a Merck executive at a deposition said the company didn't know if they ever resolved.

And six men quit the study because of the side effects, and one of them was still experiencing the side effects at least 66 days after stopping the treatment.

In the fine print of Propecia's product information material, there's a section called 'Clinical Trials Experience.'

You won't find these results there.

Merck doesn't disclose that data on the label that is shared with doctors and patients.

Merck told Reuters it disclosed all clinical trial data to the U.S. Food and Drug Administration, which approved the drug's label.

The FDA said it "takes very seriously its role in continuing to monitor and regulate the safety of drugs both before and once they are on the market."

The agency did not answer questions about how it evaluated the specific information submitted by Merck about its Propecia clinical trials.

Merck did make one small but significant change in 2002: It no longer said the symptoms resolved in "all men."

It simply said, "resolution occurred in men."

In a statement to Reuters, Merck said the "available evidence does not establish that finasteride causes sexual dysfunction which persists after drug discontinuation."

But one independent, peer-reviewed study of Propecia's side effects found they don't always stop when patients quit the drug.

(SOUNDBITE) (English) GEORGE WASHINGTON ENDOCRINOLOGIST DR. MICHAEL IRWIG, SAYING:

"Some of the men that I've studied have actually had these persistent sexual side effects for at least five or six years if notlonger, making me wonder, did this medicine do permanent damage?"

Dr. Michael Irwig is an endocrinologist at George Washington University. In a study performed on 61 former finasteride users, he found that in addition to the physiological effects, patients suffered mentally and emotionally as well.

(SOUNDBITE) (English) GEORGE WASHINGTON ENDOCRINOLOGIST DR. MICHAEL IRWIG, SAYING:

"I did a subsequent followup study, and about sixty-six percent of these men had moderate to severe depressive symptoms, and forty-four percent of them had suicidal ideations. And for a young, otherwise healthy man, who has really severe sexual dysfunction, this can make dating very difficult, or even having a relationship very difficult."

Merck says Irwig's study is flawed, citing its small sample size.

In 2008 Merck changed Propecia's label in Sweden to warn that the sexual side effects could linger even after patients stopped taking the drug.

It did not add the disclosure that year in the U.S.

In the United States, the FDA would not begin reviewing the label for nearly another three years.

2008 was the year John Pfaff started on Propecia.

One morning, five years later, John Pfaff was supposed to take his 4-year-old daughter to school but didn't.

Kelly found his wallet, cell phone and wedding band in their bedroom.

Their home in Encinitas, California, was just blocks from a train station.

The conductor of Amtrak number 562 heading south from Los Angeles told police he saw a man step out onto the tracks and face the train.

After his death, Kelly and the kids moved to Park City, Utah.

(SOUNDBITE) (English) REUTERS CORRESPONDENT DAN LEVINE, SAYING:

"Last year, Merck offered settle all of the cases, and the overwhelming majority of them settled. KellyPfaff refused to settle and is continuing to litigate her case. She's doing it partly so that other people may learn about Merck knows about Propecia and how Propecia can impact people. Her lawyers are also looking for additional information about suicide and potential suicidal thoughts."

According to data that was provided to Reuters, Propecial was prescribed over 1.6 million times in the U.S. last year alone.