Phosphodiesterase type 5 inhibitors (PDE-5 inhibitors), namely sildenafil, tadalafil, vardenafil are drugs commonly used to treat erectile dysfunction and can be consumed only on medical prescription.4-6 PDE-5 inhibitors are not recommended for patients on specific prescriptions as: organic nitrates (e.g. nitroglycerin, isosorbide dinitrate, isosorbide mononitrate, amyl nitrite, or nitrate used for the treatment of diabetes, hypertension, hyperlipidemia and ischemic heart disease), as they can cause serious and unpredictable blood pressure falls. This evidence concerns the gene PDE5A and diabetes mellitus.