Viagra (sildenafil citrate) is a drug that has been intended for the treatment of regular and more severe cases of erectile dysfunction. Make sure you take Viagra exactly as prescribed and report to your health care provider such medical conditions as high or low blood pressure, kidney disease, liver disease, chest pain, heart disease, heart attack, bleeding disorder, high cholesterol, diabetes, irregular heartbeat, blood circulation problems, stomach ulcer, pulmonary veno-occlusive disease, stroke, blood cell problems, or any conditions affecting the shape of the penis, as those may be important to determine your dose. You must never use Viagra if you are already taking isosorbide mononitrate, nitrates or isosorbide dinitrate, as interactions can be very dangerous. It is not a problem to get Viagra online, but you will need to be double careful and always check all the information available about the drug vendor you are going to place an order with. Make sure you take Viagra at least an hour before having sex and do not share it with other people to whom it was not prescribed. Your dose is based on the individual factors you have and is not supposed to be exceeded.