Fildena contains sildenafil citrate, which works by relaxing blood vessels and increasing blood flow. It does this by enhancing a natural chemical pathway involving nitric oxide (NO) and cyclic GMP (cGMP), which causes smooth muscle relaxation in blood vessels, including those in the *****. Nitrates (such as nitroglycerin, isosorbide dinitrate/mononitrate) are medications commonly used for angina (chest pain). They also increase nitric oxide in the body and strongly dilate blood vessels to reduce the heart’s workload. The danger comes when both are taken together: their effects multiply instead of simply adding up. Sildenafil blocks the breakdown of cGMP, while nitrates massively increase its production. This can lead to an excessive buildup of cGMP, causing sudden and severe widening of blood vessels throughout the body. The result is a dangerous drop in blood pressure (hypotension). This can cause dizziness, fainting, collapse, heart attack, or even stroke because the heart and brain may not get enough blood flow. In extreme cases, it can be life-threatening, especially if the person already has heart disease. Because of this risk, combining Fildena (or any sildenafil-based drug) with nitrates is strictly contraindicated. Doctors typically require a safe time gap (often at least 24–48 hours, depending on the drug and health condition) between them, and sometimes avoid the combination entirely. In short, both drugs affect the same blood-vessel relaxation pathway, and together they can push it to a dangerously high level.