Filitra 40 mg is generally a brand of vardenafil, a PDE5 inhibitor used for erectile dysfunction. However, 40 mg is above the usual maximum recommended vardenafil dose of 20 mg, so you should not take a 40 mg tablet unless a doctor specifically prescribed it. Official labeling lists 2.5, 5, 10, and 20 mg strengths. D DailyMed +1 Important precautions Never take vardenafil with nitrates such as nitroglycerin or isosorbide, or with recreational “poppers.” The combination can cause a dangerous fall in blood pressure. D DailyMed +1 Do not use it with riociguat. D DailyMed Tell your doctor if you have heart disease, low or uncontrolled blood pressure, previous stroke/heart attack, liver or kidney problems, or an abnormal heart rhythm. D DailyMed Be careful with alpha-blockers and blood-pressure medicines, because blood pressure can fall too much. D DailyMed Avoid vardenafil if you have long-QT syndrome or take certain antiarrhythmic medicines. D DailyMed Seek emergency medical attention for an erection lasting more than 4 hours, or sudden loss of vision or hearing. D DailyMed Common side effects include headache, flushing, nasal congestion, indigestion, dizziness, and nausea. D DailyMed If you tell me your age and the medicines you currently take, I can check the important interactions and whether Filitra 40 mg specifically is a concerning dose for you.