Viagra generally refers to sildenafil citrate, and the manifestation of action after taking this medication is generally shown by improved erectile function of the penis in response to sexual stimulation. Sildenafil citrate is clinically used for erectile dysfunction by increasing blood flow to the cavernous body of the penis and improving its erectile function. The use of this product requires the action of sexual stimulation in order to be effective, otherwise it will not take effect. The effects of this product are mainly manifested in the improvement of penile erectile function and increase in hardness. Adverse reactions that often occur with this product include visual abnormalities, myalgia, nausea, dizziness, skin rash, etc. It is contraindicated in patients who are allergic to this product, or in patients who are taking nitrate drugs. It is recommended to consult a physician before using the drug, choose the appropriate medication program according to the condition, and should not blindly use the drug.