I read that some of you during pct experienced a very weak sex drive, if not totally absent.

So, my question is related to the use of some stimulanting like Viagra or Cialis during pct, in case I am one of those "in trouble", in order to have sex anyway.
Is there any possible, perhaps already documented study, bad interactions among drugs usually used in pct? so nolva, clomid, hcg?

Thank you