If you are taking sildenafil to treat PAH, you will probably take sildenafil three times a day with or without food. 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. This site is intended only for U. Sildenafil is in a class of medications called phosphodiesterase PDE inhibitors. Sildenafil does not prevent pregnancy or the spread of sexually transmitted diseases such as human immunodeficiency virus HIV. The most common side effects of VIAGRA: headache; flushing; upset stomach; abnormal vision, such as changes in color vision such as having a blue color tinge and blurred vision; stuffy or runny nose; back pain; muscle pain; nausea; dizziness; rash.How much does sildenafil citrate or viagra cost near you? Find the best sildenafil citrate or viagra prices near you now with our cost comparison tool and start saving today. Nov. 1, – Jan. 2, $1, Member-only incentive on select vehicles from Chevrolet, Buick, GMC, Volvo and Polestar. Get your certificate today. Order Online and pickup at your local Costco. Find an expanded product selection for all types of businesses, from professional offices to food service operations. Our Costco .