Propecia is prescribed to slow hair loss associated with male pattern baldness and reduce symptoms of an enlarged prostate gland.

A study of Propecia (finasteride) suggests the hair loss drug’s “persistent” sexual side effects could last months or years, which raises concerns about permanent sexual dysfunction.

The study was conducted by Dr. Michael Irwig of George Washington University, who published the data in the latest issue of Journal of Sexual Medicine. According to Dr. Irwig, “20% of subjects with male pattern hair loss reported persistent sexual dysfunction for ≥6 years, suggesting the possibility that the dysfunction may be permanent.”

To conduct the study, Dr. Irwig recruited 54 adult men from an online forum for men suffering from sexual side effects of Propecia. All of the men reported at least three months of sexual dysfunction that continued even after they discontinued Propecia. When a side effect lasts for at least three months, it is described as “persistent.”

Dr. Irwig wanted to get a better idea of how “persistent” these Propecia side effects really are. All of the men in the study were followed and monitored for an average of 14 months. All of the subjects were otherwise healthy before they started taking Propecia, and had no baseline sexual dysfunction or other disorders that could skew the results.

Dr. Irwig found that 96% of the men had sexual problems for more than a year after they stopped taking Propecia. Of these, 20% reported persistent sexual dysfunction continuing at least six years after discontinuing Propecia, suggesting the dysfunction may be permanent.

Concerns Over Propecia

Propecia (finasteride) is a hair loss drug developed by Merck that works by blocking the conversion of testosterone into dihydrotestosterone (DHT), a more potent form of the hormone. It was originally developed as a way to shrink enlarged prostates.

When Propecia was first sold, experts knew that it could cause sexual dysfunction. However, the label on Propecia assured men that these sexual side effects were rare, and they would resolve when Propecia was discontinued.

However, hundreds of men have reported sexual dysfunction after discontinuing Propecia, including nearly 60 reports of dysfunction that has lasted more than three months. The FDA updated the warning label in 2011 to include the risk of persistent Propecia erectile dysfunction. In April 2012, the FDA updated this warning to include the risk of libido, ejaculation, and orgasm disorders that could last even after patients stop taking the drug.

Merck has maintained that the drug is safe, and there is no relationship between Propecia and these long-term sexual side effects.

Propecia Lawsuits

For the thousands of Propecia users who are seeking legal recourse for sexual dysfunction problems they never had before, the FDA product label update occurred too late.

The risk of sexual side effects earlier users had without the knowledge prompted thousands of men to file Propecia awsuits against Merck seeking compensation for these painful and embarrassing complications.