How do local anaesthetics stay local for several hours instead of transferring around your body through the bloodstream?

Question

How do local anaesthetics stay local for several hours instead of transferring around your body through the bloodstream?

In: 43

Answer 1

A local anesthetic will not usually last several hours but I get what you’re asking. I think of it as dropping a drop of food coloring into a bowl of water. It slowly spreads out. Any chemical like anesthetic injected under your skin does this same thing called diffusion where the molecules slowly move further and further away. It does end up in the bloodstream eventually but not nearly as fast as a drug injected directly into a vein.