Viagra is a PDE5 inhibitor that prevents the decomposition of nitric oxide. This allows more blood to enter the penis by keeping the blood arteries that supply it open longer. PDE5s are among the first-line ED treatments. A shared decision-making process should be used before offering men any ED treatment options, according to the American Urological Society.

The reported success rate for Viagra is 50–70%. Men with ED who have damaged blood vessels from smoking, high cholesterol, diabetes, or high blood pressure might not like their outcomes. Trimix can be used to treat ED in men, who cannot take sildenafil, do not want to take a pill, or experience disappointing results from sildenafil.