Erectile dysfunction is the inability to achieve or maintain an erection during intercourse that is sufficient for satisfactory sexual performance. Sometimes men have some concerns or uncertainties about sexual performance leading to the inability to maintain an erection that they experience from time to time.The problem of ED is not only dependent on age, it is also underlying health problems such as diabetes, high blood pressure, obesity, high cholesterol, chronic alcohol or drug abuse, certain medications and injuries can cause impotence. Other daily activities that can cause ED such as smoking, alcohol, etc.Viagra During sexual arousal, the blood vessels of the penis dilate, allowing the body to fill with blood and an erection occurs. The blood vessels that are supposed to drain blood are temporarily closed so that the erection is maintained. With erectile dysfunction, insufficient blood enters or does not stay in the penis, causing an erection to weaken quickly. The PDE5 inhibitors present in Viagra inhibit the breakdown of vasodilators.Viagra comes in tablets of 25, 50 and 100mg. Your doctor will prescribe the exact dose. Take the tablets with a glass of water on an empty stomach, approximately one hour before sexual activity. Do not use Viagra more than once a day or it will increase the risk of side effects.