Viagra is just a common name, in clinical medicine is known as sildenafil, this kind of drug is the treatment of male erectile dysfunction, and there is no so-called how old to take the best statement. For normal men there is no need to take sildenafil, only in the case of erectile dysfunction can be applied. It can be taken when erectile dysfunction is present and there is no such thing as the best age to take it. The drug is usually taken about an hour before sex and can improve the hardness and duration of erections. Sildenafil belongs to the category of prescription drugs, so you must be prescribed by a doctor to buy and take, do not blindly buy and use, so as to avoid side effects, such as dizziness, nausea, flushing and so on, thus affecting the health of the body, and sildenafil can not be used at the same time with nitrate drugs, drug allergy, women, children, and other people are prohibited to use. Drugs should be selected under the guidance of a professional doctor to avoid abusing drugs by yourself.