Oral ED medicines might not work or might be dangerous if you also take any of the following: Nitrate medicines. Read on ED medications like Viagra or its generic form Sildenafil might be a little tricky to figure out right off the bat. Vardenafil usually works for 4 to 5 hours. At Strut , we offer prescription ED treatments like Sildenafil or Tadalafil online through a quick online questionnaire-based telemedicine consultation with our U. If you have an erection that lasts more than 4 hours, get medical help right away. An inherited eye disease that affects the retina.Medically reviewed by Alex Brewer, PharmD, MBA Updated on October 12, Viagra (sildenafil) is a brand-name prescription drug that’s used to treat erectile dysfunction . Sildenafil is best known as a treatment for ED, the inability to get or keep an erection. Sildenafil is meant to be taken before having sex, with the understanding that its effects . Sildenafil (Viagra, Revatio) is a moderately priced drug used to treat erection problems in test1.ru is also used to treat pulmonary arterial hypertension, a serious heart and lung .