Lidocaine Mechanism of Action and Safety Guidelines

Introduction to Lidocaine Mechanism

The American College of Medical Toxicology recommends that lidocaine works by blocking voltage-dependent sodium channels and pH-dependent receptors in multiple systems, producing local anesthetic, analgesic, and antiarrhythmic effects, but with a very narrow therapeutic window where central nervous system toxicity begins at plasma levels only slightly higher than therapeutic concentrations (>6 mcg/mL) 1, 2

The American Heart Association suggests that lidocaine blocks sodium ion channels necessary for the initiation and conduction of neuronal impulses, resulting in local anesthesia after application 3
The European Society of Anesthesiology states that at therapeutic concentrations, lidocaine blocks muscarinic and NMDA receptors, while at concentrations close to toxic, many additional types of receptors are affected, including Nav1.8/1.7, nicotinic cholinergic receptors, and voltage-dependent calcium channels 1, 2

The American Academy of Clinical Toxicology notes that systemic absorption can occur from multiple sites: inadvertent intravascular injection, topical application on traumatized or septic mucous membranes, and intrapleural instillation 2
The National Institute of Health guidelines indicate that liver insufficiency reduces lidocaine clearance by 60% in patients with liver dysfunction, with a risk of toxicity including myocardial depression, somnolence, disorientation, muscle spasms, and convulsions 3

The American College of Emergency Physicians recommends that the maximum safe dose is 4-4.4 mg/kg without epinephrine or 7 mg/kg with epinephrine; exceeding these limits dramatically increases the risk of convulsions 1
The European Resuscitation Council states that factors increasing the risk of convulsions even at therapeutic doses include liver dysfunction, heart failure, cardiogenic shock, acidemia, hypoalbuminemia, and concomitant medications such as beta-blockers and amiodarone 1

The American Heart Association suggests that immediate treatment requires discontinuation of lidocaine, airway management, control of convulsions with benzodiazepines, and intravenous lipid emulsion (ILE) 1
The American Academy of Clinical Toxicology recommends that 20% lipid emulsion should be immediately available where lidocaine is used, and all staff should know its location for immediate treatment of systemic toxicity 2