Sildenafil (the active ingredient in Viagra) is a drug that people use only when they need it. It is a phosphodiesterase type 5 inhibitor approved by the Food and Drug Administration (FDA) for erectile dysfunction (ED). It works by increasing blood flow to the penis, making it easier to get and keep an erection. Sildenafil is the right choice for those that want a drug to work fast, as it only takes 30 minutes to 1 hour to take effect before sexual activity, and the effects typically last for 3-5 hours. The dose depends on the severity of the condition ranging between 30-100mg (most common is 50mg, so you get 12 doses from our 6-pill prescription)