Viagra is a drug that is taken to help men who suffer from a very common problem called erectile dysfunction or male impotence. The medication has undergone extensive testing before being approved to be sold on the market and has helped millions of men treat their condition successfully. The drug works very well to increase blood flow to your penis, thus enabling you to achieve and sustain an erection when engaging in sexual intercourse. However, there are a few precautions you need to be aware of. First, Viagra only works in conjunction with sexual stimulation. Eating a high-fat meal beforehand may also increase the amount of time it takes for Viagra to work. It usually takes the drug less than an hour to become effective if you take the pill without eating, and the effects generally last from 4-6 hours. If you are suffering from male impotence, talk to your doctor about trying Viagra.