RE: Sildenafil (Viagra), what is its mechanism of action?

Great post, thanks! Can you write about tadalafil? Its better than sidenafil? I have been using Tadalafil 5mg in cycles (usually weekends) because I take an antidepressant that affects my sex drive a little bit, but it has more to do with libido than with circulation or physical dysfunctions, I would really like to find a solution for the libido, but tadalafil already gives a legal help at least, even if it is more related to the durability of the erection.