Quebec's highest court has authorized a class-action lawsuit on behalf of men who took medication for hair loss and then allegedly suffered various problems, including erectile dysfunction.

The defendants are Merck Canada and Merck Frosst Canada, which sold the Propecia and Proscar prescription drugs.

Propecia is used mainly to treat baldness, while Proscar is used primarily to treat enlargement of the prostate. Both contain the active ingredient finasteride.

The lawsuit covers Quebec men who were prescribed one of the two drugs before Nov. 18, 2011, and claim they developed problems that lasted even after they stopped using them. The claims have not been tested in court.

The problems included erectile dysfunction, lower libido levels, ejaculation issues, shrinkage of the genitals and difficulty in having an orgasm.

It is alleged that doctors prescribed Proscar for hair loss.

Lower court decision appealed

Lawyers at the firm of Trudel Johnston & Lesperance who launched the legal action said they are happy with the Quebec Court of Appeal's decision to authorize the lawsuit but they did not want to comment further.

Attorneys for Merck did not immediately respond to a request for an interview.

A lower court nixed the idea of a lawsuit in 2016.

But the appeals court ruled Quebec Superior Court imposed too much of a burden on lead plaintiff Camilo Baratto, who is in his early 40s.

The three-judge appeals panel said the lower court, without having to at that stage of the proceedings, took a position on the scientific debate surrounding the medication and its effects.

The high court said the debate must take place but not at the stage of the authorization.

Baratto says he started taking Proscar for his baldness in October 2008 by cutting the pills to bring the dose closer to that of Propecia.

He states he stopped the medication after one month because he was starting to have side-effects such as a drop in libido, erectile and ejaculation problems, anxiety and depression symptoms.

Baratto, who says he is still suffering today from some of the secondary effects, acknowledges the potential risks were mentioned on the container but not the fact they could continue once he stopped taking the drug.

He alleges the two companies changed the wording in Switzerland in 2008 but failed to do so in Canada until November 2011.

Baratto's suit is seeking at least $100,000. The amount for those who will join the action has yet to be determined, but $10,000 in punitive damages is being sought for each.