Welcome to the Liquid Stunning

Did you know that Novacaine stays in one location because it contains epinephrine (aka adrenaline) - which shrinks your blood vessels and disables them from taking the anesthetic away from the location of the insertion!  So, it lasts several hours, until the hormone breaks down and the blood vessels go back to normal and whisk the anesthetic away where it is cleansed from the system in the liver. 

Individuals with heart problems cannot have Novacaine because of this hormone additive; therefore they have to get injected with a less potent anesthetic agent called...something...which only lasts about 25 minutes and isn't as effective.

I asked my dentist, while drooling and numb and bored in his chair!