An erection results from an increase in blood flow to the penis. Rogue pharmacies are not licensed to sell in the United States and put you at risk of counterfeit or tainted drugs How Many Online Pharmacies Are There? Psychological factors like stress, depression, or anxiety can also contribute. That’s not to say there aren’t just as many illegitimate sites. Still other online pharmacies specialize in medications for only a select few health concerns or conditions.Depending on your symptoms and needs, you may be prescribed Viagra, sildenafil, Cialis, tadalafil, Stendra, paroxetine, or a combination of tadalafil and sildenafil, available as . An FDA investigation found that more than one-third of “dietary supplements” sold for ED actually contained prescription drugs, including sildenafil, the medicine in Viagra. Some . Sildenafil (Viagra, Revatio) is a moderately priced drug used to treat erection problems in men. It is also used to treat pulmonary arterial hypertension, a serious heart and lung .