These are reliable sources for sildenafil safety precautions: NHS — Sildenafil safety, side effects and interactions — practical patient guidance. NHS MedlinePlus — Sildenafil precautions — interactions and precautions to discuss with your doctor. MedlinePlus DailyMed — Official sildenafil prescribing information — detailed contraindications and drug interactions. VIAGRA- sildenafil citrate tablet, film coated The most important precautions: Never combine sildenafil with nitrate medicines such as nitroglycerin or isosorbide, or with riociguat. Tell your doctor or pharmacist about all your medicines, especially heart and blood-pressure medicines. MedlinePlus +1 If you experience chest pain after taking Cenforce Soft, seek emergency medical help and tell the clinicians when you took it. Do not take nitroglycerin yourself.