Viagra is the trade name, generically known as sildenafil citrate, and the initial dose usually lasts 20 to 40 minutes. Sildenafil citrate is a medication that is used to treat erectile dysfunction in men and is usually better when taken 30 to 60 minutes before the start of sexual intercourse. After taking Sildenafil Citrate, dizziness, flushing, nasal congestion, abdominal pain, diarrhea and other symptoms may occur. It is forbidden to combine with nitrate drugs, and this drug is contraindicated for women, those who are allergic to this product, children, and those who are not suitable for sex in recent cardiovascular status. If you need to take sildenafil citrate, it is recommended to prescribe this drug under the guidance of a doctor according to the patient’s condition, self-administration may increase the risk of medication.