Viagra generally refers to sildenafil citrate, the efficacy and function of the treatment of erectile dysfunction; suffering from cardiovascular and cerebrovascular diseases, allergic to this product, and the application of nitrate drugs and other people, should be prohibited from using this drug. Sildenafil citrate enhances the nitric oxide (NO)-cGMP pathway through selective inhibition of PDE5, elevates cGMP levels and leads to relaxation of penile cavernous smooth muscle, resulting in a natural erectile response to sexual stimulation in patients with erectile dysfunction. In clinical practice, it is mainly used for the treatment of male erectile dysfunction. It should be noted that this drug should be contraindicated in people who are allergic to the drug, or in people who have recently applied guanylate cyclase agonists and nitrate drugs; patients with serious cardiovascular and cerebrovascular diseases, or those who have developed serious cardiac arrhythmia or myocardial infarction within six months should use this drug with caution; and patients with sickle-cell anemia and pigmented retinitis should be used with caution. Patients may experience nausea, diarrhea, abdominal pain, dyspepsia, rash, dizziness and visual abnormalities after using the drug. The specific use of the drug must follow the doctor’s instructions; any adverse reactions after the use of the drug, you should seek medical treatment as soon as possible.