Viagra is the trade name, generic name is sildenafil citrate, more than 40 years old to eat sildenafil citrate, the dose of 25 ~ 100 mg ranging, the specific eat how much with personal constitution and also the content of the drug and so on a variety of reasons related to the doctor’s guidance in accordance with the instructions for the correct use. Sildenafil citrate is a drug for the treatment of male erectile function, can improve the male sexual life ability, promote the vascular supply of the cavernous body of the penis, can maintain a very good erection hardness and erection time, usually taken 1 hour before sex, more than 40 years of age, the normal amount of 50 mg or so, if the effect is not obvious can be increased to 100 mg, the effect is better, can be reduced to 25 mg. Some people taking sildenafil citrate may have symptoms such as flushing, nausea, vomiting, blurred vision, and can not be overdosed, it may lead to erectile difficulties, or even permanent inability to get an erection, but also produce dependence, heart disease, diabetic patients can not take. It should be taken correctly under the guidance of a doctor, and usually pay attention to develop good habits, no smoking and no alcohol.