The nonprofit watchdog group Public Citizen has filed a lawsuit on behalf of the Post-Finasteride Syndrome Foundation (PFSF), which, in 2017, petitioned the FDA to pull the hair loss drug Propecia (finasteride) from the market.

The lawsuit, which was filed in the U.S. District Court for the District of Columbia, asks the court to force FDA to issue a decision on PFSF’s petition within 30 days of the Court’s order.

Merck is the manufacturer of Propecia, which first won FDA approval for male pattern baldness in 1997. Propecia is a 5-alpha reductase inhibitor.

PFSF’s 2017 petition to FDA cites evidence of adverse events including depression and suicidal ideation.

The drug has also been linked to post-finasteride syndrome (PFS), which involves a constellation of adverse side effects.

The lawsuit cites PFS as a syndrome appearing in peer-reviewed studies that can afflict men for “​​years after they have stopped taking finasteride.”

Post-Finasteride Syndrome Foundation describes PFS as involving “persistent sexual, neurological, physical and mental adverse reactions in patients who have taken finasteride.”

Researchers are divided on the nature of the syndrome. A 2020 article in Neurobiology of Stress concluded that PFS is an “emerging clinical problem.” Conversely, another article published that same year in Fertility and Sterility asks whether PFS is “a real clinical condition caused by finasteride use.” Finally, a 2019 article in Skin Appendage Disorders concludes that the drug has “demonstrated both a high efficacy of treatment and a very favorable safety profile, establishing the drug as first-line treatment of male pattern hair loss.” It goes on to ask whether PFS is an “induced delusional disorder.”

Other studies have concluded that finasteride can have sexual and psychological side effects, including suicidal ideation in some men.

Regulatory bodies in Canada and Europe have added warnings about suicidal ideation and ideation to finasteride.

Finasteride first won FDA approval in 1992 as the Proscar, which is indicated at a 5-mg dose to treat symptomatic benign prostatic hyperplasia.

Propecia is a brand name for 1 mg of finasteride.

Demand for the drug has grown in recent years, and generic versions have been available since 2006. U.S. prescriptions have doubled from 2015 to 2020, according to the Post-Finasteride Syndrome Foundation lawsuit.