Is there biological plausibility?
To bolster its argument that finasteride has dangerous psychiatric side effects, the advocacy organization cited a study first published in JAMA Dermatology in late 2020 that investigated suicidality and psychological adverse events in patients taking finasteride.
David-Dan Nguyen, MPH, and his colleagues at Brigham and Women’s Hospital in Boston, McGill University, Montreal, and the University of Montreal, examined the VigiBase database and found 356 cases of suicidality and 2,926 psychological adverse events; cases were highest from 2015 to 2019.
They documented what they called a “significant disproportionality signal for suicidality (reporting odds ratio, 1.63; 95% confidence interval, 2.90-4.15) and psychological adverse events (ROR, 4.33; 95% CI, 4.17-4.49) with finasteride, especially in younger men and those with alopecia, but not in older men or those with benign prostatic hyperplasia.
The study authors noted that some studies have suggested that men with depression have low levels of the neurosteroid allopregnanolone, which is produced by the 5-alpha reductase enzyme. Finasteride is a 5-alpha reductase inhibitor.
According to Public Citizen’s lawsuit, “The product labeling does not disclose important information about finasteride’s mechanism of action,” and “the drug inhibits multiple steroid hormone pathways that are responsible for the formation of brain neurosteroids that regulate many critical functions in the central nervous system, like sexual function, mood, sleep, cognitive function, the stress response, and motivation.”
Dr. Jacobs said that “there’s a lot of good solid high-quality research, mostly in animals, but also some on humans, showing a plausible link between blocking 5-alpha reductase in the brain, deficiency of neuroactive steroids, and depression.”
The author of an accompanying editorial, Roger S. Ho, MD, MPH, an associate professor in the department of dermatology, New York University, was skeptical. “Without a plausible biological hypothesis pharmacodynamically linking the drug and the reported adverse event, this kind of analysis may lead to false findings,” Dr. Ho said in the editorial about the Nguyen study.
Dr. Ho also wrote that he believed that the lack of a suicidality signal for dutasteride, a drug with a similar mechanism of action, but without as much media attention, “hints at a potential reporting bias unique to finasteride.”
He recommended that clinicians “conduct a full evaluation and a detailed, personalized risk-benefit assessment for patients before each prescription of finasteride.”
Important medicine, important caveats
Dr. Jacobs said that many of the men who come to him with side effects after taking finasteride have “been blown off by most of the doctors they go to see.”
Urologists dismiss them because their sexual dysfunction is not a gonad issue. They are told that it’s in their head, said Dr. Jacobs, adding that, “it is in their head, but it’s biological.”
The drug’s label advises that sexual side effects disappear when the drug is stopped. “That’s only true most of the time, not all of the time,” said Dr. Jacobs, adding that the persistence of any side effects impacts what he calls a “small subset” of men who take the drug.
“We have treated tens of thousands of patients who have benefited from the medicine and had no side effects,” said Dr. Bernstein. “But there is a lot that’s still not known about it.”
Even so, “baldness in young people is not a benign condition,” he said, adding that it can be socially debilitating. “An 18-year-old with a full head of thick hair who’s totally bald in 3 or 4 years – that can totally change his psyche,” Dr. Bernstein said. Finasteride may be the best option for those young men, and it is an important medication, he said. Does it need to be used more carefully? “Certainly you can’t argue with that,” he commented.
Dr. Bernstein and Dr. Irwig reported no conflicts. Dr. Jacobs disclosed that he is an expert witness for the plaintiffs in a suit against Propecia maker Merck.