What effect does infection and inflammation have when administering local anesthetic?

Infection and inflammation significantly influence the pharmacological behavior of local anesthetics. When there is inflammation or infection in tissues, the pH of the affected area becomes more acidic. This change in pH affects the ionization of the local anesthetic. Most local anesthetics are weak bases and, in an acidic environment, they exist predominantly in their ionized form, which is less capable of penetrating nerve membranes and, as a result, blocks the action of the anesthetic.

Moreover, inflammation usually increases vascularity in the affected area. Enhanced blood flow facilitates the rapid absorption and systemic distribution of the anesthetic agent, leading to more rapid inactivation of the local anesthetic. Hence, the anesthetic effect may be reduced due to its quicker clearance from the site of action compared to normal tissue.

This understanding highlights the importance of considering tissue condition (e.g., presence of infection or inflammation) when planning anesthesia, especially in surgical contexts. In contrast, inflamed tissues do not result in increased effectiveness or duration of action for local anesthetics; instead, these factors tend to diminish the efficacy of the anesthetic agent in clinical practice.