Name: Lidocaine (Xylocaine)
Class: Local Anesthetic (Amide)
Mechanism: Blocks Na+ & Ca2+ channels ® ¯ rate of rise of action potential, failure to propagate action potential, eventual conduction block. Smaller, unmyelinated fibers are more easily blocked and remain blocked longer.
Absorption: Rapidly absorbed IV & oral. IV absorption can be limited w/a vasoconstrictor. Rapid topical absorption at mucous membranes.
Dist.: Rapidly dist. to highly perfused organs (i.e., brain, liver, kidney, heart).
Metabolism.: Metabolism. by liver microsomal enzymes.
Excretion, t½: Med. duration of action.
Toxicity/S.E.s: Progressive CNS effects—agitation leading to convulsions, generalized CNS and resp. depression, CV depression, death.
Utility: Surface anesthesia, infiltration anesth., field block anesth., nerve block anesth., IV regional anesth., spinal anesth., epidural anesth.
Special Features: 4x as potent as procaine. Sometimes used w/epinephrine to prolong action and decrease system toxicity.