Viagra is great for some, for some it won't have any great benefit and a select few will have severe side effects.
PDE5's lower blood pressure, so anyone who already suffers from low blood pressure or who take beta blockers, should be cautious.
Always start with a low dose, no more than 50mg and increase dosage if there are no effects.
PDE5's ONLY work when there is no venous leak, ie, they only help with blood flowing into the penis, they will not work if blood flows out quicker than it flows in.
You need to be sexually aroused, they do NOT make a man last longer, but some men can stay hard even after they orgasm.
Headaches, blurred vision, blue vision, nauseous and a increased heartbeat are all common side effects.
I preferred Cialis, less side effects and the effects last longer if not quite as potent.