Propecia, a hair loss medication originally designed to treat prostate symptoms, has been linked to the occurrence of sexual dysfunction in some patients.

The link has led to a trend of Propecia lawsuits, several hundred of which have been consolidated in both state and federal court.

Propecia is manufacturer Merck’s brand name for the drug known generically as finasteride drug known generically as finasteride. Finasteride was originally developed as a treatment for benign prostatic hypertrophy, or BPH, and approved by the FDA for that use under the brand name Proscar.

During clinical trials, researchers noticed that men taking finasteride as a BPH medication also experienced extra hair growth. Merck then developed finasteride as a treatment for hair loss, and in 1997 the FDA approved finasteride for that use under the brand name Propecia.

Propecia works by inhibiting the enzyme that converts testosterone to the stronger androgen dihydrotestosterone, or DHT. DHT that is present in the scalp can shrink hair follicles and cause hair loss.

Propecia has the effect of reducing DHT by up to 60 percent in men who take it daily. In clinical trials, that reduction in DHT stopped hair loss in 86 percent of the trial subjects.

Sexual Side Effects of Propecia

But after Propecia began to be used as a treatment for hair loss, the FDA began receiving reports of Propecia side effects from patients experiencing various types of sexual dysfunction. In April 2012, the FDA announced a revision to the label for Propecia, expanding the list of sexual side effects that had been reported to the agency.

The new label noted that Propecia users had reported problems with libido, ejaculation and orgasm disorders that persisted after they stopped using Propecia. The agency also added mention of male infertility and poor semen quality that did improve after discontinuation.

The FDA based the change in part based on 421 reports of Propecia side effects received in the agency’s Adverse Event Reporting System between 1998 and 2011. Fifty-nine of these reports noted that sexual dysfunction continued for at least three months after discontinuing Propecia.

More recently, a study published in Hormone Molecular Biology and Clinical Investigation found that men who took finasteride experienced significant gradual decrease in their erectile function. The same men exhibited a decline in total testosterone levels. The Boston University researchers noted that in some cases the sexual side effects of Propecia were persistent.

Propecia Litigation

Merck has faced hundreds of Propecia lawsuits over sexual side effects allegedly attributable to Propecia. Generally, the plaintiffs in these and other Propecia lawsuits allege that Merck failed to properly warn doctors and their patients about the risks of Propecia side effects.

Some spouses of men who took Propecia are making their own claims for loss of consortium, based on the effect of Propecia side effects on their marital relationship.

In the federal court system, more than 700 Propecia lawsuits have been consolidated into a single multidistrict litigation based in a federal court in Brooklyn. The federal court system sometimes consolidates large numbers of similar cases into a multidistrict litigation, or MDL, to coordinate pretrial procedures.

In 2012, other Propecia lawsuits in New Jersey state court were similarly consolidated into a single court in Middlesex County, where Merck’s corporate headquarters is located.

The Propecia MDL is In re: Propecia (Finasteride) Products Liability Litigation, MDL No. 2331 in the U.S. District Court for the Eastern District of New York.