Do not take sildenafil with similar medications such as avanafil (Stendra), tadalafil (Cialis) or vardenafil (Levitra). Tell your doctor about all other medications you use for erectile dysfunction.
Do not take sildenafil if you take other medicines to treat pulmonary arterial hypertension, such as riociguat (Adempas).
Do not take sildenafil if you are also using a nitrate drug for chest pain or heart problems. This includes nitroglycerin, isosorbide dinitrate, and isosorbide mononitrate. Nitrates are also found in some recreational drugs such as amyl nitrate or nitrite ("poppers"). Taking sildenafil with a nitrate medicine can cause a sudden and serious decrease in blood pressure.
In addition, tell your doctor about all your other medicines, especially:
drugs to treat high blood pressure or a prostate disorder;
antifungal medicine - ketoconazole or itraconazole; or
medicine to treat HIV/AIDS - ritonavir and others.
This list is not complete. Other drugs may interact with sildenafil, including prescription and over-the-counter medicines, vitamins, and herbal products. Not all possible drug interactions are listed here.
 Sildenafil drug interactions (more detail)
