Litigation over Propecia side effects is growing while patients continue to discover sexual side effects that linger after discontinuing the drug.

Propecia is Merck’s brand name for finasteride, a drug that prevents testosterone from being converted to dihydrotestosterone.

Merck originally developed finasteride as a treatment for benign prostatic hyperplasia (enlargement of the prostate). The FDA approved it for that use in June 1992.

But during the trials for that approval, researchers noticed some patients showed increased hair growth. Merck then sought approval to use the same drug as a male pattern baldness treatment. With approval for that use in December 1997, Propecia entered the market.

Propecia works by inhibiting the action of an enzyme called 5-alpha-reductase, the enzyme responsible for converting testosterone into dihydrotestosterone, or DHT. In balding scalp, the presence of DHT causes hair follicles to shrink, and that shrinkage ultimately contributes to hair loss.

Propecia reduces levels of DHT in the scalp by as much as 60 percent. Less DHT means less hair follicle shrinkage, and the progression of male pattern baldness is slowed.

However, men who took Propecia have reported certain sexual side effects. One patient who started taking Propecia at age 24 reported loss of libido, erectile dysfunction, and pain in the testicles.

After he stopped taking Propecia, some side effects went away while others lingered. In a follow-up report 11 years later, the patient reported continuing to suffer from erectile dysfunction and lost sex drive.

In April 2012, the FDA required an update to the labeling for Propecia to enhance the warnings about sexual side effects. Added to the list of such side effects were “libido disorders, ejaculation disorders, and orgasm disorders that continued after discontinuation of the drug.”

The FDA also required the label to describe reports of male infertility and lessened semen quality that improved or resolved after discontinuing the drug.

The FDA determined the need for a labeling change based on 421 after-market reports of sexual dysfunction submitted to the agency’s Adverse Events Reporting System from 1998 to 2011.

Fifty-nine of those reports described sexual side effects of Propecia that lasted three months or more after the patients stopped taking Propecia.

The FDA also identified 251 reports of reduced semen quality associated with a Propecia regimen, though only 13 of those cases contained enough information for the agency to evaluate them.

Propecia Lawsuits

Patients affected by lingering side effects of Propecia have begun seeking legal redress en masse. In April 2012, the federal Judicial Panel on Multidistrict Litigation consolidated nine federal Propecia lawsuits into a single multidistrict litigation, or MDL, to be conducted in the U.S. District Court for the Southern District of New York.

Since then, the number of the cases in the MDL has grown to over 700. Hundreds of Propecia lawsuits in New Jersey state court have been similarly consolidated in the Superior Court for Middlesex County.

Consolidations like these are common in large-scale product liability litigation, in which several individual claims will share common factual and legal issues. By dealing with pretrial matters at once in a single court, courts can make more consistent decisions on a more timely basis.