Viagra should take approx. 1 hour before you plan to have sex. You take effect after about 25 minutes and lasts for 4-5 hours. When you are sexually stimulated, the body sends out neurotransmitters that will make you get an erection. Blood vessels dilate and blood flow to the so-called corpora cavernosa of the penis. Viagra works by enhancing the effects of these neurotransmitters and therefore not an erection without being sexually stimulated. 62-82% have improved their potency problems using Viagra. You can take a maximum of one dose per day. The most common starting dose is 50 mg, and one should not take more than 100 mg at one time. Side Effects is not uncommon. Headache and flushing seen more frequently among those who use Viagra. In addition, heartburn, nasal congestion dizziness and temporary changes in color vision among the possible side effects. Palpitations are also reported. The side effects usually lasts briefly and goes away by itself. Viagra is engaged in sexual disorders such as impotence or erectile dysfunction is used. If in doubt you should always consult a doctor or pharmacist. They also have all of incompatibility should be reported. Basically Viagra should not be taken unless there is some hereditary diseases of the retina. When the retina is affected due to these diseases in the operation or damage the cell structure in the course of the disease, should be made of any account of this potency drugs. If other potency drugs used to prevent the use of Viagra. This also applies to children and adolescents under 18 years. Moreover, people should do without having to low blood pressure (hypotension) to the intake of Viagra. In this case, there may be a greater drop in blood pressure, which can sometimes result in disastrous consequences. The diseases of the heart, blood circulation problems, should disorders of the liver and stomach ulcers be Viagra is not mutual. This applies especially for men who tend to have a permanent erection. It must be treated immediately in all cases and is very painful. At worst, it may result in damage to tissue and presenting a permanent impotence with it. Similarly Viagra should be used when there are anatomical deformity of the penis. The typical side effects when taking Viagra without prescription may occur, but need not, include headache a flush. This redness is supposed to follow a heightened sense of warmth. Sometimes, the veil of other symptoms, including vision and irritability of the stomach. It is characterized particularly by the feeling of fullness, but can go hand in hand with the same abdominal pain upper abdomen an early satiety, nausea and vomiting and heartburn. Also feel the nose is stuffy. Very rare and long lasting erections happen, which should be treated immediately.