I have seen the sexual side effects appear after a man has been on the drug for months or years. The incidence reported of 2-4% was reported over a 5-year period of time, but I agree with you, that it may be more than the reported numbers. Most people, when they get off the drug, will find that the sexual side effects disappear in a month or two.
11 months of finasteride use, but side effects are becoming increasingly real from tressless
2018-01-09 06:59:462018-01-28 09:02:06Finasteride side effects slowly came on (from Reddit.com)