In statements of claim filed in Regina and Calgary, two men say they lost interest in sexual activity after taking Propecia.
The claims, which have not been proven in court and have yet to be certified as a class-action, allege that drug maker Merck Frosst Canada didn't adequately warn people about the risks of Propecia.
Sexual dysfunction is listed as a possible side effect to the drug.
But the men allege that Merck didn't properly warn people that sexual dysfunction could continue even after they stopped taking the treatment.
A call to Merck was not immediately returned Friday.
According to the Regina statement of claim, the man started taking Propecia after having a lump on his head removed in December 2007. His doctor gave him a free sample to encourage hair growth where the lump had been and a prescription for more.
The man claims he noticed hair wasn't growing on his head, but in rather large patches on his neck and back. He also alleges he noticed a decrease in his sex drive and had difficulty maintaining an erection.
The statement of claim in Calgary was filed on behalf of a man who started on Propecia in 2000 and took it for four years.
The man claims his relationship with his wife suffered and they grew apart because his sex drive decreased.
Regina lawyer Tony Merchant, who filed the claim, argues the warning about the side effect wasn't good enough.
"The drug companies, not just in this case but in others, then say, 'number 1, we had this warning there.' But what they really mean is it's buried somewhere and it's not a meaningful warning of any kind," said Merchant.