Vilitra is a PDE-5 inhibitor (vardenafil). Nitrate drugs (nitroglycerin, isosorbide mononitrate/dinitrate, nitrite medicines, and many “nitro” preparations) increase nitric oxide → raise cGMP. PDE-5 inhibitors block cGMP breakdown, so together they potentiate vasodilation and can produce severe hypotension, fainting, heart attack, stroke, or even death. some small pharmacology studies suggest the interaction with sildenafil or vardenafil may no longer be measurable after ~24 hours, and for tadalafil after ~48 hours — but regulatory labels for Vilitra still state co-administration with nitrates is contraindicated and say a “safe” time interval has not been established, so you cannot rely on a fixed safe window without medical guidance. In emergencies (chest pain), tell EMS you recently took Vilitra.