Finasteride โ or Propecia, its most popular brand name โ was invented by Merck. The pharmaceutical company insists that it's rare for men on the medication to experience side-effects, and has long maintained they vanish once the medication is stopped.
But 25 people interviewed by CBC/Radio Canada during a six-month investigation of finasteride's side-effects tell a different story. They say the drug caused sexual, psychological and physical side-effects for them that have lasted months if not years after they ceased taking the drug.
The men interviewed by CBC/Radio-Canada said their symptoms are debilitating: loss of libido, erectile dysfunction, infertility, cognitive and physical issues, anxiety, insomnia, depression and, in many cases, suicidal ideation.
"It's a complete chemical castration where you have no chemical reaction to anything sexual, anything in life," said Michael, a British Columbia man who says his symptoms have lasted more than 15 years.
"It's important to remember that the majority of patients will not experience permanent symptoms with this type of medication," he said. "The problem is that we don't know which men could develop these symptoms or why."
(emphasis mine)
Since its launch, Propecia's product monograph has mentioned the risk of side-effects such as decreased libido, erectile dysfunction and ejaculation disorder, but states that "the incidence of each of the above side-effects decreased to โค0.3 per cent by the fifth year of treatment."
In these internal exchanges, however, a Merck scientist calls this safety data "misleading." He points out that to achieve such a low number, his colleagues had excluded all men who had left the studies because of sexual side-effects.
While the company has long claimed that side-effects disappear when users stop the drug, other internal emails suggest some of the clinical trial participants did have persistent adverse effects after cessation.
"Nothing has been reported about these men who developed these persistent side-effects. So we don't know if they ever recovered or not," said Irwig.