PDE5 inhibitors, known as sildenafil, tadalafil, and elidel, are prescription drugs and should not be taken without a doctor’s prescription. Sildenafil can inhibit the production of phosphodiesterase in a targeted manner, which can improve blood flow in patients with pulmonary hypertension by relaxing vascular smooth muscle and causing vasodilatation, which in turn leads to better blood flow. In addition, PDE5 inhibitors such as sildenafil, tadalafil and vardenafil are also the first-line treatment drugs of choice for erectile dysfunction in clinical practice. PDE5 specifically inhibits PDE5 activity in the penile corpus cavernosum to maintain high levels of cGMP in smooth muscle cells, thereby achieving and maintaining an erection. Because of its specific action on PDE5 in the penile corpus cavernosum, it does not affect other sites of phosphodiesterase. In addition, it should be noted that PDE5 inhibitors have certain side effects, mainly facial flushing, headache, dyspepsia, etc. The incidence is about 10%, the degree is mild to moderate, the duration is short, usually without special treatment, can be self-relieved.