51% of Dermatologists Believe Finasteride ‘May Cause’ Sexual Side Effects—but Only 18% Believe those ADRs May Persist, Says New Harvard Medical School Research

Pioneering PFS investigator Michael Irwig also finds that just 13% of respondents believe finasteride could cause depression, while 54% believe the drug is ‘unlikely’ or ‘very unlikely’ to do so

Aug. 16, 2023

Dear Friends:

Despite the fact that the finasteride product label has included depression and persistent loss of libido as possible side effects going back more than a decade, the majority of dermatologists are either unaware or skeptical of these potential adverse reactions.

That, according to a new survey by Michael S. Irwig, MD, of Harvard Medical School.

Dr. Irwig, an endocrinologist practicing at Beth Israel Deaconess Medical Center, also found that 31% of dermatologists said that when starting their patients on finasteride, they would counsel 0% to 25% of them on the drug’s potential to cause persistent sexual side effects. Only 40% of the respondents, however, said they would counsel 76% or more of their patients on the drug’s to cause persistent sexual side effects.

Titled Beliefs and Counseling Practices Among Dermatologists Regarding Sexual and Other Adverse Effects of Finasteride, the study—which Irwig says was prompted by the fact that “several review articles and commentaries on ‘post-finasteride syndrome’ question its existence”—was published Aug. 4 in the International Journal of Impotence Research.

In all, Irwig and his team of four researchers surveyed 100 dermatologists and resident dermatologists at two annual meetings: American Academy of Dermatology, held in March 2022 in Boston, and the Society for Investigative Dermatology, held in May 2022 in Portland, OR.

“This study…identifies the need for greater awareness of the potential adverse effects of finasteride from the increasing number of studies that include randomized controlled trials as well as retrospective studies and post-marketing reports,” writes Irwig.

Depression and persistent loss of libido were first added to the finasteride label in 2012. Five years later, drug regulatory authorities (DRAs) outside the US (such as in Austria and South Korea) began warning of suicidal ideation among finasteride users. A year after that, in 2018, finasteride originator Merck itself, via Direct Healthcare Professional Communications (aka Dear Doctor letters), began warning of suicidal ideation in Saudi Arabia and other nations.

In the US, however, the Food and Drug Administration didn’t add suicidality of any sort—ideation, behavior or completed—until 2022.

(For more information on how DRAs the world over have been monitoring finasteride adverse events, disclosing risks to the public, and regulating the medication, see our PFS Global Warning Map.)

Among other key findings from Irwig’s survey:

• Of the 90 respondents that initiated at least one patient on finasteride, 21% of dermatologists and 25% of dermatology residents reported that at least one of those patients suffered persistent sexual side effects.

• Male dermatologists/residents were more likely than female dermatologists/residents (63% vs. 44%) to counsel at least half of their patients about potential persistent sexual side effects arising from finasteride use.

• Of the 56 respondents who filled in the free-text question, 57% were able to define “post-finasteride syndrome.” Definitions that referenced both sexual symptoms and persistent symptoms were counted as correct.

Along with Roberto Cosimo Melcangi, PhD, at the University of Milano, and Abdulmaged M. Traish, PhD, at Boston University, Irwig is one of three pioneers who have been investigating PFS in excess of a decade.

His first such study, titled Persistent Sexual Side Effects of Finasteride for Male Pattern Hair Loss, was published in 2011 in The Journal of Sexual Medicine. It concluded, in part:

A subset of otherwise healthy men taking finasteride for [male pattern hair loss] developed persistent sexual side effects in temporal association with the medication. Most men developed sexual dysfunction in multiple domains with 94% experiencing low libido, 92% experiencing erectile dysfunction, 92% experiencing decreased arousal, and 69% experiencing problems with orgasm. The mean duration of the persistent sexual side effects was at least 40 months, with 20% of subjects reporting durations of over 6 years.

Most recently, prior to his finasteride-beliefs survey, Irwig published Finasteride and Suicide: A Postmarketing Case Series. For that 2020 study, in Dermatology, he examined six cases of PFS suicide, based on medical records and autopsy reports provided by family members. Those patients, who lived in the USA, the UK and France, began taking finasteride between the ages of 19 and 36 years, and died between the ages of 25 and 42.

“The most prominent psychiatric symptoms were depression, anxiety, panic attacks, feelings of isolation and brain fog,” while “Some of the most debilitating symptoms were insomnia and fatigue,” he wrote.

“Clinicians should be aware that men under the age of 40 who use finasteride for alopecia are at risk for suicide if they develop persistent sexual adverse effects and insomnia.”

In all, Irwig has published nine PFS studies, and one PFS commentary, in peer-reviewed journals:

Persistent sexual side effects of finasteride for male pattern hair loss: The Journal of Sexual Medicine, 2011

Persistent sexual side effects of finasteride: could they be permanent? The Journal of Sexual Medicine, 2012

Depressive symptoms and suicidal thoughts among former users of finasteride with persistent sexual side effects: The Journal of Clinical Psychiatry, 2012

Decreased alcohol consumption among former male users of finasteride with persistent sexual side effects: a preliminary report: Alcohol Clinical & Experimental Research, 2013

Androgen levels and semen parameters among former users of finasteride with persistent sexual adverse effects: JAMA Dermatology, 2014

Persistent sexual and nonsexual adverse effects of finasteride in younger men: Sexual Medicine Reviews, 2014

Safety concerns regarding 5α reductase inhibitors for the treatment of androgenetic alopecia: Current Opinion in Endocrinology, Diabetes and Obesity, 2015

Finasteride and Suicide: A postmarketing case series: Dermatology, 2020

How routine pharmacovigilance failed to identify finasteride’s persistent sexual side effects: Andrology, 2022

Beliefs and counseling practices among dermatologists regarding sexual and other adverse effects of finasteride: International Journal of Impotence Research, 2023

Anyone living in the US who suffers from PFS should report his or her symptoms to the US FDA. Anyone living outside the US who suffers from PFS should report his or her symptoms to the US FDA as well as to his or her local drug-regulatory authority (DRA), as directed on our Report Your Side Effects page.

Finally, if you or a loved one are suffering from PFS, and feeling depressed or unstable, please don’t hesitate to contact the PFS Foundation as soon as possible via our Patient Support hotline: social@pfsfoundation.org.

Thank you.

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