Viagra is the trade name, generic name is sildenafil citrate tablets, some people can have intercourse about once or twice after taking this product. Sildenafil Citrate Tablet is a 5-type phosphodiesterase inhibitor, which can treat erectile dysfunction and can improve the hardness of penile erection. After patients take it, the effect of the drug can last for 4 to 6 hours, and during the effective time, they can have sex 1 or 2 times when their physical strength allows. Adverse effects of Sildenafil Citrate Tablets may be angina pectoris, atrioventricular block, migraine and so on. Sildenafil is forbidden to be combined with nitrate drugs, this drug is contraindicated in women, people who are allergic to this product, children, people whose recent cardiovascular state does not allow them to have sex. However, taking sildenafil citrate tablets is only for temporary relief of symptoms, and can not completely cure impotence, so after finding out the disease should be strictly in accordance with the requirements of the doctor’s treatment.