Local anesthetics

Local anesthetics

Clinical data
Pharmacodynamics
Pharmacokinetics
Physical and chemical data
Article quality
Editor rating	In development
User likes	0

Local anesthetics are the defining medication class for regional and local anesthesia. They transiently inhibit sensory, motor, and autonomic nerve function depending on location/route of administration and dosage.

Pharmacology

Pharmacodynamics

Mechanism of action

Local anesthetics target voltage-gated sodium channels. Local anesthetic binding to the α subunit prevents channel activation and sodium influx through the channel, resulting in decreased sodium conductance across the membrane. Thus, the threshold for excitation and impulse conduction in the nerve increases, and the rate of rise and magnitude of the action potential decreases. Impulse conduction velocity is also slowed. Of note, this does not alter the resting membrane potential.

Local anesthetics have greatest affinity for the Na channel in the open or inactivated state as opposed to the resting state. Thus, depolarization favors local anesthetic binding.

Sensitivity of nerve fibers to local anesthetics depends on axonal diameter and myelination. Larger, faster-conducting fibers (Aα) are less sensitive to local anesthetics than smaller, slower fibers (Aδ). Additionally, small, unmyelinated C fibers are more resistant than larger myelinated fibers.