Amid ongoing litigation over adverse side effects of Propecia, a new study has found multiple inadequacies in the trials used to determine the safety of this men’s health drug.

Propecia, or finasteride, is a drug designed and made by Merck & Co. as a male pattern baldness treatment. Merck originally designed the drug as a treatment for benign prostatic hyperplasia (BPH), and it was for that use that the FDA originally approved finasteride in 1992 under the trade name Proscar. Later, the FDA approved it for the treatment of androgenic alopecia, or male pattern baldness.

Propecia works by inhibiting the activity of an enzyme that converts testosterone to dihydrotestosterone. This action tends to decrease androgen activity in both the prostate and the scalp, reducing both prostatic hyperplasia and hair loss.

The new Propecia study was conducted by a team from the Feinberg School of Medicine at Northwestern University. Researchers examined 34 clinical trials used to assess the safety of finasteride, the active ingredient in Propecia, as a treatment for androgenic alopecia. The study found that none of those trials had adequate safety reporting. Additionally, more than half of the trials were funded by the drug’s manufacturer, leading at least 18 of the articles to disclose that their authors had conflicts of interest.

Notably, most of the Propecia safety articles did not report certain important details about symptoms of sexual dysfunction, which is the set of Propecia side effects that has been the subject of so many recent Propecia lawsuits.

The Propecia side effects study concluded that the toxicity information yielded in these trials was of poor quality and appeared to be systematically biased. According to the study’s lead author Dr. Steven Belknap, the trials simply did not yield enough information to determine whether or not Propecia is safe for use.

Litigation over Propecia Side Effects

Although no research has ever found a causal relationship between finasteride and male infertility, the FDA began receiving hundreds of reports of sexual dysfunction coinciding with use of Propecia. Based on the findings of these reports, the FDA ordered Merck to include a warning about sexual dysfunction on their Propecia label in 2010.

These claims of sexual side effects have resulted in a wave of Propecia lawsuits. Merck is currently facing over 1,200 lawsuits based on the finasteride side effects of both Propecia and Proscar. Plaintiffs allege Propecia side effects they experienced while on the Merck drug include: erectile dysfunction, loss of sex drive, inorgasmia, and shrinking of the genitals, as well as non-sexual side effects such as cognitive impairment. These Propecia side effects can reportedly continue even after the patient stops taking Propecia, and some claimants have alleged the effects are permanent.

Propecia lawsuits typically allege that Merck failed to adequately warn patients and physicians about the adverse side effects of Propecia. It is also typical for pharmaceutical products liability lawsuits like these Propecia cases to make claims of negligence, misrepresentation, defective design, defective manufacturing, and breach of warranty.

In April 2012, a large number of federal Propecia lawsuits were consolidated into one multidistrict litigation, or MDL. This 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.