The generic name of Viagra is sildenafil citrate, and after taking sildenafil citrate drugs, the effect takes effect in about 30 to 120 minutes and lasts for about 0.5 to 4 hours or so after taking them with sexual stimulation. Sildenafil is an effective drug for the treatment of erectile dysfunction in men, mainly through the inhibition of 5-phosphodiesterase activity, to achieve the effect of enhancing and maintaining penile hardness. Since its blood concentration peaks in about 30 to 120 minutes, its onset of action is generally within this range, and the drug’s effects can be maintained for about 0.5 to 4 hours. The drug can also affect the cardiovascular and circulatory functions of men, some patients may experience mild dizziness, dizziness and nausea after taking the drug, which can cause slight dilation of peripheral blood vessels, manifested as redness of the face, headache, dizziness, nasal congestion, drop in blood pressure, prolonged erection of the penis, which is an adverse reaction of the drug. Sildenafil enhances the antihypertensive effect of nitrate, and is contraindicated in patients taking any dosage form of nitrate, either regularly or intermittently. The drug should be used under medical supervision.