Abstract
Local anesthetics have been used as therapeutic agents for well over 100 years. The primary effects of local anesthetics occur at the site of administration by inhibiting the propagation of action potentials in sensory neurons. In medical practice today, local anesthetics have a wide range of uses, from numbing tissue for dental procedures to migraine headache prevention and surgical site-specific peripheral regional anesthesia. Cocaine is the first known local anesthetic and is a natural product, but its abuse potential (see Chapter 24) limits its clinical use. All other local anesthetics available today are synthetic derivatives of cocaine that lack the high abuse potential and have fewer side effects or toxicities. Local anesthetics are considered to be safer than intravenous (IV) or inhaled general anesthetics (see Chapter 26), especially for patients with significant comorbidities or who may have a genetic predisposition for adverse reactions to general anesthetics (e.g., malignant hyperthermia). However, severe side effects and death may occur if local anesthetics are administered improperly or given to patients with heart disease or history of seizures who could be at higher risk of developing local anesthetic systemic toxicity (LAST). The specific local anesthetics given and the location, as well as the type of administration (e.g., topical, subcutaneous injection, epidural injection, etc.), determine, in large part, the duration and depth of anesthesia. Since all local anesthetics are derivatives of cocaine, they have similar chemical structures and side effects, and they share the same mechanism of action.