A Connecticut law firm has filed a lawsuit against pharmaceutical manufacturer Merck & Co. on behalf of men who have taken Propecia, a prescription drug that combats hair loss but, its critics say, can also cause severe side effects such as sexual dysfunction and mental impairment.

Attorney Edward Jazlowiecki of Bristol has joined two other firms, in New Jersey and New York, in filing the suit, which alleges that Merck has failed to fully disclose the serious side effects of Propecia and failed to adjust its warnings in the American market even after European regulators forced the company to carry a stronger warning label.

Propecia, which is also marketed under the brand name Proscar, was originally introduced to treat men with enlarged prostates, but it won FDA approval in 1997 for the treatment of male pattern hair loss after patients noticed its restorative powers with hair. The drug's active ingredient is finasteride, which can help reduce the levels of the substance on the scalp that leads to hair loss.

But in many men, Jazlowiecki said, finasteride also reduces sexual function and leads to mental and emotional symptoms like anxiety attacks and insomnia that do not go away years after men stop using the drug.

"The same mechanism in the hormone system that controls hair loss also controls sexual function and a patient's mental state, and this drug has had devastating effects and destroyed the lives of men who have taken it," Jazlowiecki said. "Merck knew this, and their claims that the negative effects of the drug go away once you stop using it are false. The damage to these men appears to be permanent, even after five years of taking the drug."

When contacted by The Courant, Merck released a statement that said, "The company intends to vigorously defend against the lawsuit."

Jazlowiecki said that one of the plaintiffs in his suit suffered such severe symptoms that his wife left him, and that another plaintiff suffered from a loss of concentration that forced him to drop out of law school. Jazlowiecki's complaint, filed in U.S. District Court in New Jersey, where Merck's U.S. headquarters are located, also quotes American and European doctors who have passionately argued against the drug, citing many of the severe side effects listed in the lawsuit.

Similar experiences are described on a website devoted to men who have suffered side effects from the drug, http://www.propeciahelp.com.

One Connecticut patient, who plans to join the lawsuit as soon as lawyers finish examining his medical records, said that he stopped taking Propecia three years ago after experiencing trouble breathing, sexual dysfunction, anxiety attacks and memory loss. He asked not to be named because his mother still does not know of the severe side effects the drug caused.

"I was a happy, athletic person before I started taking this drug, but now it has ruined my life," the plaintiff said. "The hardest part is going to doctors and describing my condition and they don't believe me. They believe all of the material that has been sent out by the FDA and Merck and just send me home with a prescription for anti-depressants."

On its Propecia website, under "possible side effects," Merck does have a warning, which reads:

"A small number of men had sexual side effects, with each occurring in less than 2% of men. These include less desire for sex, difficulty in achieving an erection, and a decrease in the amount of semen. These side effects went away in men who stopped taking PROPECIA because of them."

But doctors that Jazlowiecki quotes in his lawsuit insist that symptoms persist after patients stop using Propecia, and might be permanent.