Viagra is also known as sildenafil citrate, imported and domestic from the efficacy of no essential difference, just price differences. Imported drugs and domestic drugs, the active ingredients of the drug are the same, so there is no essential difference in efficacy, can play a role in the treatment of erectile dysfunction. There is a difference in price: domestic drugs cost about $50 to $400, and imported drugs cost about $70 to $600. Common adverse reactions, there are gastrointestinal reactions, dizziness and headache, increased heart rate and so on. It is prohibited for those who are allergic to the drug, and those who take nitrate drugs are prohibited from using it. If you need to use the drug, you need to check with a doctor first and use the drug under the doctor’s guidance.