Viagra is so popular that its name has become synonymous with ED treatment — just like Ziploc has with plastic bags. But the active ingredient in Viagra is sildenafil. Pfizer Pharmaceuticals patented ...
Sildenafil is a prescription drug. It comes in the form of a tablet and suspension (liquid). Both are taken by mouth. It also comes in an intravenous (IV) form, which is only given by a doctor.