Sildenafil does not prevent pregnancy or the spread of sexually transmitted diseases such as human immunodeficiency virus HIV. Some people may also have ringing in their ears tinnitus or dizziness. Make sure to get an estimate of when you can expect your prescription in the mail. Some services offer a subscription option where they’ll send your medications every month at a discount. There are no antidotes available for sildenafil.Who may not be able to take sildenafil. Sildenafil is not suitable for some people. To make sure it’s safe for you, speak to your doctor or pharmacist before taking sildenafil if you: have ever had an allergic reaction to sildenafil or any other medicine. have recently had a stroke, heart attack or a heart problem – your doctor should. About sildenafil (Viagra) Sildenafil is a medicine used to treat erection problems (erectile dysfunction). Sildenafil is also sometimes used to treat pulmonary hypertension (high blood pressure in the blood vessels that supply the lungs). If you have erection problems sildenafil works by temporarily increasing blood flow to your penis when. Medications Prescribed: Viagra, Cialis, Cialis Daily, Levitra, tadalafil, sildenafil, vardenafil. Generic offered: Yes. Why We Chose It. The simple combination of Rex MD’s online platform, its helpful customer service, and the abundance of ED treatment options make it a one-stop shop for all your sexual health needs.