This drug is a type 5 phosphodiesterase (PDE5) inhibitor. Oral administration of this drug can effectively improve the quality and duration of erection, and improve the success rate of life in men with erectile dysfunction. The initiation and maintenance of penile erection is related to relaxation of cavernose smooth muscle cells, and cyclic guanosine phosphate (cGMP) is the mediator of relaxation of cavernose smooth muscle cells. This drug prevents the breakdown of cGMP by inhibiting phosphodiesterase type 5, resulting in the accumulation of cGMP, relaxation of the smooth muscle of the spongy body, and erection of the . Compared with phosphodiesterase isoenzyme 1, 2, 3, 4, 6, this drug has high selectivity to phosphodiesterase type 5. Data showed that its selectivity and inhibitory effect on phosphodiesterase type 5 were superior to other phosphodiesterase type 5 inhibitors, and it was speculated that this selectivity might lead to fewer cardiovascular and visual adverse reactions than other phosphodiesterase type 5 inhibitors.