Hiya, My wife and i were trying for a few years without success of a child. I decided to start taking finasteride (1mg a day) as i thought it effected my sperm so i held off. 5 months later whilst taking finasteride, we are now expecting our first child, due may 10th. So in answer to your question... no it cant be used.. in my case, my semen was a little bit watery and i can only assume that the looser nature of it, it was able to flow better.
thanks
and as a side note, the clinic that examined my sperm noticed no difference in the quality of it. (we went through IVF)