Increased sensitivity to the active agent or any of the excipients of the drug. Simultaneous use of nitric oxide donors (such as amyl nitrite) or nitrates in any form is contraindicated because it is known that the effect of sildenafil is in the path of metabolism of nitrogen monoxide / cyclic guanosine monophosphate (cGMP) and potentiates the hypotensive effects of nitrates. Medicines for the treatment of erectile dysfunction, including sildenafil, are contraindicated for men who are not recommended to have sexual activity (eg, patients with severe cardiovascular disorders such as unstable angina and heart failure, severe). Patients with loss of vision in one eye due non-arterrial ischemic optic neuropathy, regardless of whether the pathology associated with previous use of PDE5 inhibitors. Patients with the following diseases: liver dysfunction, severe, hypotension (blood pressure lower than 90/50 mm Hg.), Recent stroke or myocardial infarction and known hereditary degenerative retinal disorders such as retinitis pigmentosa (a small amount of patients have genetic disorders of retinal phosphodiesterases) because the safety of sildenafil has not been studied in these patient subgroups.