Sildenafil is primarily a drug used to treat penile erectile dysfunction, also called Viagra, is a selective phosphodiesterase inhibitor. It mainly acts on the enzyme phosphodiesterase, and by inhibiting the enzyme, the vascular smooth muscle of the corpus cavernosum is relaxed, allowing blood to flow into the corpus cavernosum and realize the function of erection. But in the absence of sexual stimulation, the recommended dose of sildenafil usually does not work. In the clinic, it is mainly used for patients with erectile dysfunction, but special care needs to be taken when using it, and the patient’s past medical history must be noted. If the patient has a history of cardiovascular disease, such as myocardial infarction, hypertension, coronary heart disease, angina pectoris, the use of the drug is not recommended, because the drug may cause a series of adverse reactions of the cardiovascular system. In addition, when the drug is used, the dosage of the drug and the timing of the drug is also very important, must comply with the recommendations of the doctor, the rational use of drugs, can not increase the dose or unauthorized increase in the frequency of the drug. In short, sildenafil is the treatment of erectile dysfunction drugs, can effectively treat erectile dysfunction, and must be in this situation with sexual stimulation, it is a better therapeutic effect.