Men with erectile dysfunction and impotence can be treated with purple pill viagra. Follow your doctor's advice when taking this medication. This medication takes five hours to take effect. Take this medication half an hour prior to sexual activity so that you can enjoy quality time with your companion. This medication takes four to six hours to take effect. This medication can also be taken both before and after a meal. Sildenafil Citrate, a component in this medication, helps men ejaculate for longer periods of time. As prescribed by your physician, you should take this medication. Only guys who are at least eighteen years old should use this medication.