According to Drugs.com, Novocain lasts for an average of 1 to 1.5 hours. The drug has a rapid onset of action, typically 2 to 5 minutes.
The duration of action may be extended if a vasoconstrictor is administered alongside the Novocain, delaying the system's absorption of the drug. Other factors that can affect the duration of action include the concentration used, the particular characteristics of the patient and the anesthetic technique used. Drugs.com states that Novocain is a local anesthetic that is administered as an injection during surgical, dental and other medical procedures. Novocain may produce allergic reactions and other side effects.