Sildenafil can be taken by patients with three high blood pressure, but they need to follow their doctor’s instructions. Sildenafil belongs to highly selective phosphodiesterase-5 inhibitors and is a carbon monoxide donor. It has the effect of diastolic vascular smooth muscle in the clinic. The administration of sildenafil leads to relaxation of the smooth muscle of the corpus cavernosum of the penis, resulting in a natural erectile response to sexual stimulation in patients with erectile dysfunction. Since phosphodiesterase-5 does not exist in normal or diseased cardiac conduction tissue, cardiomyocytes, or endothelial cells, sildenafil does not have a positive inotropic effect, and therefore cannot affect myocardial contractility. Sildenafil may cause flushing, headache, diarrhea, rash and other symptoms after taking it. Because of its antihypertensive effect, it can not be combined with nitrate drugs, and is prohibited for those who are allergic to the components of the drug. In conclusion, patients with three high blood pressure can take sildenafil to treat erectile dysfunction as prescribed by their doctors. If dizziness, nausea and other uncomfortable symptoms occur during the course of taking the drug, it is recommended to stop taking the drug and consult a doctor immediately.