The chemistry and pharmacology of local anesthetics.

The most common local anesthetics in clinical use today are of two classes: amino-esters and amino-amides. These two classes differ not only in their chemical structure but also in regard to their metabolism and allergic potential. Potency, onset of action, duration of action, and relative blockade of sensory and motor fibers are important clinical properties of local anesthetics. These clinical properties are related to the physiochemical properties of lipid solubility, pKa, and protein binding. The effects of local anesthetics are primarily caused by the blockade of the sodium channels, thus affecting the slow and fast depolarization phase of the action potential. With the basic understanding of the chemistry and pharmacology of the different local anesthetic agents, the nurse anesthetist can more effectively integrate the use of these drugs into their clinical practice.