Viagra , the oral medication for treating impotence, has raised more than the obvious. Most people have lots of questions -- from how it's used and how it affects a couple's relationship, to whether women can benefit from it. So here are the facts about what Viagra can do and what it can't do. Viagra is by far the most widely used treatment for ED. In the United States, more than 5 million men just like you have turned to Viagra to improve their sexual function. Doctors in the United States have prescribed Viagra more than 16 million times. And Viagra is available in more than 90 countries worldwide. Up to 82% of patients who take Viagra experience an improvement in their erections. That means more than 4 out of every 5 couples who try Viagra benefit from it. Viagra improves erections in most men regardless of how long they have had ED, what caused it, or how old they are. And the effectiveness of Viagra has been proven in clinical studies of thousands of patients. Viagra is a prescription medication, so you'll need to talk to your health care provider to find out if it's right for you. Be sure to ask your health care provider if your heart is healthy enough to handle the extra strain of sexual activity. If you have chest pains, dizziness, or nausea during sex, stop and immediately tell your health care provider. With Viagra , the most common side effects are headache, facial flushing, and upset stomach. Viagra may also briefly cause bluish or blurred vision, or sensitivity to light. In the rare event of an erection lasting more than 4 hours, seek immediate medical help. Remember to protect yourself and your partner from sexually transmitted diseases.