Local anesthesiaLocal anesthesia is defined as a loss in the perception of pain over a small area of the body. Regional anesthesiaRegional anesthesia is a loss in the perception of pain, but in a larger anatomical area or region. Both local and regional anesthesiaRegional anesthesia are typically induced through the topical application or injection of pharmacological local anesthetic agents There are two types of local anesthetic agents which are defined by their chemical structures: amidesAmide and estersEster. Both classes exert their effects by deactivating the sodium channels responsible for the inward flux of sodium during the depolarization phase of the action potential. The net result is an increase in the amount of stimulus required to generate an action potential, as well as decreased propagation of action potentials across the anesthetized neuron. This chapter will discuss the history, pharmacology, pharmacokinetics, metabolism, toxicities, chemical structures, as well as the clinical utility of using local anesthetics in localized and regional fashion.