Local anesthetics.

PURPOSE OF REVIEW: Local anesthetics are used in a wide range of clinical situations to prevent acute pain and to stop or ameliorate pain produced by cancer or pain associated with chronic painful conditions. Knowledge of the pharmacology of local anesthetics is essential for their safe use and selection of specific agents to achieve intended goals.

RECENT FINDINGS: Local anesthetics are a group of drugs defined by their ability to prevent sodium entry into axons, thereby preventing the generation of propagated action potentials in axons. They have other actions, however, such as prevention of axonal sprouting and effects on G-protein-coupled receptors, and on conductance of ions in addition to sodium that might be important in the management of pain. The recent literature focuses on the spectrum of pharmacodynamic actions of local anesthetics, on comparison of pharmacodynamic and pharmacokinetic properties of racemic mixtures versus solutions of pure enantiomer, and on formulations to prolong duration of action. There is new evidence that lipid suspension is useful in the treatment of bupivacaine cardiac toxicity.

SUMMARY: Local anesthetics have similar chemical structure but differing pharmacokinetic properties and spectra of pharmacodynamic effects that influence selection of agents for use in various clinical situations.