Viagra is a sexual health product and generally does not cause side effects, so everyone should read the instructions carefully before using it to get the best understanding of how to use it. After using Viagra, you can last for one hour at a time, which is at least double the previous life time. Therefore, in the process of living, you can obviously feel that your body functions are significantly improved. During the use of Viagra, it will not cause any irritating effects on the body, nor will it cause damage to the kidneys and lungs.