Other conditions that may disqualify you from an ED prescription include a history of stroke, kidney or liver disease, cancer, diabetes, or a bleeding disorder. In some patients, the use of VIAGRA with alpha-blockers can lead to a drop in blood pressure or to fainting medicines called HIV protease inhibitors, such as ritonavir Norvir , indinavir sulfate Crixivan , saquinavir Fortovase or Invirase , or atazanavir sulfate Reyataz some types of oral antifungal medicines, such as ketoconazole Nizoral and itraconazole Sporanox some types of antibiotics, such as clarithromycin Biaxin , telithromycin Ketek , or erythromycin other medicines that treat high blood pressure other medicines or treatments for ED VIAGRA contains sildenafil, which is the same medicine found in another drug called REVATIO. Take sildenafil exactly as directed. Levitra vardenafil : This medication is taken one hour before sex and can last up to 24 hours. If you are taking sildenafil to treat PAH, you will probably take sildenafil three times a day with or without food. Follow-up support: Make sure you can get the help you need if questions or concerns arise after ordering. These PDE5 inhibitors may cause headache, flushing, drop in blood pressure, or other adverse effects.You can take all of them with or without food. However, taking Viagra, Levitra, or Stendra after eating a high fat meal does slow the rate of absorption. (brand name and generic) even without. Eligible patients could save up to $4, a year. Savings Card only works on brand name. If you are enrolled in a state or federally funded prescription insurance program, you may . 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.