Local Anesthetics Mechanism

Local anesthetics act on the sodium channels and most effective on activated neurons. They block the entry of Na+ ions and hence action potential is interrupted and stopped.

LA receptors are present on the inner side of the cell membrane.

So, they have to penetrate the cell membrane first to go and bind with the receptor. They enter as unionized form and then gets ionized and binds with the receptor on the inner cell membrane.

In case of an infected region, the local anesthetic will be ionized faster before penetrating the cell membrane because of the acidic medium.

So we need more dose of anesthetic in such case.