Sildenafil does not prevent pregnancy or the spread of sexually transmitted diseases such as human immunodeficiency virus HIV. Before starting, stopping, or changing any medications while taking sildenafil, please get the advice of your doctor or pharmacist. Make sure you have discussed any other medications you are currently taking or plan to take before starting sildenafil with your doctor and pharmacist. Recent heart or blood vessel problems. Sildenafil is also used in both men and women to treat the symptoms of pulmonary arterial hypertension. On 6 May , Pfizer , which manufactures Viagra, told the Associated Press they will begin selling the drug directly to people on its site. This, in my view, is the key issue in this appeal.Dizziness, headache, flushing, or stomach upset may occur. Vision changes such as increased sensitivity to light, blurred vision, or trouble telling blue and green colors apart may also occur. If. Viagra (sildenafil) is an oral drug that is used for treating impotence (or erectile disfunction, ED, the inability to attain or maintain a penile erection). It is in a class of drugs called phosphodiesterase inhibitors (PDE-5 inhibitors) that also includes. tadalafil (),; vardenafil (Levitra, Staxyn ODT), and; avanafil ().; It has been estimated that impotence . Sildenafil (Liqrev, Revatio) is used to improve the ability to exercise in adults (Liqrev, Revatio) and children 1 year of age and older (Revatio) with pulmonary arterial hypertension (PAH; high blood pressure in the vessels carrying blood to the lungs, causing shortness of breath, dizziness, and tiredness).