My grandfather is currently taking finasteride for prostate reasons. Even though it is the 5mg pill, I couldn’t help but notice that sexual side effects such as ‘impotence’ and ‘abnormal ejaculation’ were listed under ‘Common’. Not uncommon, not rare, but common! That being said, how ‘common’ is common? Are side effects in general rare, but sexual dysfunction is the most persistent of the side effects? When you quote a 2% chance of being subjected to sexual side effects, of what number is that 2% drawn from? Are sexual side effects rarer in
Propecia because of its smaller (1mg) dose?

Most of the studies on 1-2% sexual dysfunction is derived from the Prosar (finasteride 5mg dose). Taking a smaller dose should give you less side effect but the reported side effect is still around 1-2%.
This is taken directly from the MERCK website Propecia insert:
“In three controlled clinical trials for PROPECIA of 12-month duration, 1.4% of patients taking PROPECIA (n=945) were discontinued due to adverse experiences that were considered to be possibly, probably or definitely drug-related (1.6% for placebo; n=934). Clinical adverse experiences that were reported as possibly, probably or definitely drug-related in ?1% of patients treated with PROPECIA or placebo are presented in Table 1.”


