Merck & Co. is defending more than 1,240 lawsuits from approximately 1,500 men who claim the company’s hair loss drugs Propecia and Proscar caused them to suffer permanent sexual dysfunction – an undisclosed side effect of the drugs’ active ingredient finasteride.

On Monday, April 13, five additional Propecia lawsuits were filed, signaling a long road ahead for Merck in the legal battle over whether the company concealed the permanent nature of finasteride side effects on male sexual health.

One of those Propecia lawsuits, filed Monday by Pennsylvania plaintiff Gus H., is seeking over $75,000 in damages for “severe sexual dysfunction” allegedly caused by finasteride side effects.

Gus says he was prescribed Propecia in 2006 at the age of 46 to treat male pattern hair loss. Prior to using Propecia, he did not suffer from sexual dysfunction but now continues to suffer from adverse side effects despite discontinuing Propecia treatment in 2009.

“Plaintiff has significant pain and suffering, and his quality of life has been severely diminished,” his Propecia lawsuit states. Now he requires ongoing treatment including regular medical monitoring of his persistent sexual dysfunction.

His allegations echo those made by thousands of men.

The Truth about Finasteride Side Effects

Finasteride, the active ingredient in Propecia and Proscar, was initially developed to treat patients with symptoms of benign prostatic hyperplasia (“BPH”), and then later approved for the treatment of androgenic alopecia, also known as male pattern hair loss.

Male pattern hair loss affects 30% of men by the age of 30 years and 50% of men by the age of 50 years. The condition is thought to be caused by a combination of genetic factors and a hormone called dihydrotestosterone (“DHT”), a substance in the body that can shrink hair follicles until a person no longer has hair. Finasteride decreases the conversion of testosterone to DHT, therefore, preventing hair loss.

While a successful hair loss treatment for men, finasteride has been shown to cause undesirable side effects in some men, including but not limited to sexual disorders like decreased libido, erectile dysfunction and ejaculation disorder.

“The rates of the sexual dysfunction as a result of finasteride are reported to be as high as 39% in published clinical studies. In addition, it has been reported in 2003 that only 50% of patients experience resolution of their sexual function adverse events after discontinuation of finasteride,” the Propecia lawsuit filed by Gus states.

In 2008, following an investigation by the Swedish Medical Products Agency into reports of persistent sexual dysfunction in men who stopped taking finasteride, Merck changed the Propecia label in Sweden to include a warning for “persistence of erectile dysfunction after discontinuation of treatment with Propecia.” The company also changed labels in other European companies such as Italy and the United Kingdom.

It wasn’t until an April 2012 label change mandated by the FDA, however, that Merck finally updated the drug warning label for U.S. Propecia prescriptions to indicate that patients have reported “difficulty in achieving erection that continued after stopping the medication.” But the warning still fails to warn users that Propecia sexual dysfunction can be persistent or permanent, plaintiffs allege.

As a result, Gus and more than 1,500 other men are suing Merck for violations ranging from negligence and failure to warn to defective design, strict liability, breach of warranty, fraud, fraudulent concealment, and more.

Gus’s Propecia Lawsuit is Case No. 15-cv-2067, filed in the U.S. District Court for the Eastern District of New York under finasteride MDL No. 12-MD-2331.