Viagra, whose chemical name is sildenafil, is a type 5 phosphodiesterase inhibitor, whose main effect is to treat male erectile dysfunction, and is also one of the main drugs for the treatment of male erectile dysfunction, and is generally taken about 30 minutes before sex, and requires sexual stimulation after taking in order to play the drug effect. It should be used with caution or prohibited for patients with coronary heart disease, severe hypotension and cardiac insufficiency, and is strictly forbidden to be combined with nitrate drugs to avoid severe hypotension. In addition, sildenafil can also be used to treat pulmonary hypertension, either alone or in combination with other drugs.