If Fildena 50 contains sildenafil 50 mg, certain people should avoid it or use it only after medical assessment: People taking nitrate medicines such as nitroglycerin or isosorbide, because the combination can cause a dangerous drop in blood pressure. People taking riociguat, a guanylate-cyclase stimulator, because combining it with sildenafil can also cause significant hypotension. Anyone allergic to sildenafil or any ingredient in the product. Men for whom ***** activity is medically inadvisable because of cardiovascular disease should be assessed by a clinician before using sildenafil. People taking alpha-blockers or certain blood-pressure medicines may need a lower sildenafil dose and medical supervision because blood pressure can fall further. For standard sildenafil ED treatment, 50 mg is the usual recommended starting dose, but the appropriate dose varies by individual. It should generally be taken no more than once per day. If you develop chest pain, sudden vision/hearing loss, fainting, or an erection lasting more than 4 hours, seek urgent medical care.