Viagra stops the return of blood flow from the penis.
“When a man is sexually excited, the arteries in the penis relax and widen. This allows more blood to flow into the penis. The increased blood flow causes the penis to become hard and erect. The veins that normally carry blood away from the penis then become compressed. This restricts the blood flow out of the penis. With more blood flowing in and less flowing out, the penis enlarges, resulting in an erection. “
In the case of using it for recreational purposes, the action of the drug is often confused with the desire of the man anyway. Performance anxiety is often settled with the thought that its going to work anyway since you took the V. This is a good reason to use it on itself. If your taking it mainly for performance issues, then just try 25mg first and go from there.
I have used it for the extreme pump it provides through its action, stopping the return of blood. Also since i am multi orgasmic, its nice to be able to go soft then crank it back up within minutes.