Sildenafil citrate is a common drug used in the treatment of erectile dysfunction and pharmacologically, it is an inhibitor of phosphodiesterase type 5. Usually in the presence of sexual stimulation, it increases the amount of nitric oxide in the cavernous body of the penis, causing the smooth muscle cells inside the cavernous body of the penis to relax, which increases the blood flow introduced into the cavernous body, promoting erection and increasing erection hardness. The time to take it is 1-3 hours before sexual intercourse. It has some common adverse reactions, such as headache, facial flushing and indigestion, but the incidence of this part of adverse reactions is relatively low and mild.