The scientific name of Viagra is sildenafil, which belongs to the category of phosphodiesterase inhibitors, and its main efficacy is that it can improve the erectile function of the penis in men, and is used to treat erectile dysfunction. Sildenafil is taken 0.5 hours before the start of sexual intercourse, and it is effective within 4 hours, that is, the efficacy of the drug can be maintained for about 4 hours, during which time if there is sexual stimulation it can improve the state of penile erection function in men. However, without sexual stimulation, men do not have the urge of sexual excitement and will not cause penile erection, can avoid causing abnormal erection of the penis. Therefore, sildenafil is currently the drug of choice for the treatment of erectile dysfunction in men, and has a relatively good therapeutic effect on improving various types of erectile dysfunction, with an overall therapeutic effectiveness rate of more than 80%.