Sildenafil can not be purchased directly in the pharmacy, you need to have a formal prescription issued by a physician to buy and use. Sildenafil belongs to the national prescription drugs, according to the relevant prescription drug management regulations, can not be purchased directly in the pharmacy, you must have a prescription issued by a physician to purchase and use. Sildenafil was first used for the treatment of pulmonary arterial hypertension, in the process of use was found to have the effect of helping erection, later gradually become a class of drugs used to treat erectile dysfunction. Common adverse reactions reported in clinical trials include headache, dyspepsia, abnormal vision, nasal congestion, back pain, myalgia, nausea, dizziness and rash. Sildenafil is prohibited in combination with nitrates, and the drug is contraindicated in women, people who are allergic to the product, children, and people whose recent cardiovascular status makes sexual intercourse inadvisable. If you need to use the relevant drugs, please go to the regular hospital after consultation by a specialist physician prescribed, follow the specialist physician’s medical advice to use.