How oral medicines differ Each oral medicine for ED has a slightly different chemical makeup. Since some medicines can cause poor erectile function, your doctor might immediately get to the cause. These medicines all work well for ED. Kidney disease that needs to be treated with dialysis. The easiest way to do this is by asking a question. If this occurs, the urologist will have more information and will need less time to diagnose your condition.It’s important to be honest about your other prescriptions, so your doctor can give you the best advice about taking Viagra. Viagra shouldn’t be used with medications that lower . I mean who is he to say it shouldn’t be used. It IS a legal drug. Every doctor has to use his professional opinion for EVERY prescription that he gives and each patient is different. . Generic Viagra (sildenafil) is available as a , , , and milligram (mg) pill and in liquid form. It’s meant to be taken as needed — about an hour before sex — but .