Local Anesthetic Agents

Local Anesthetic Agents

Classification

• Amino Amides:
  • Most commonly used local anesthetics
  • Examples: lidocaine, mepivacaine, prilocaine, articaine
• Esters:
  • Older local anesthetics, less commonly used
  • Examples: tetracaine, benzocaine, procaine
• Amphipathic:
  • Combination of amino amide and ester structures
  • Example: ropivacaine

Mechanism of Action

• Local anesthetics work by blocking the generation and conduction of nerve impulses
• They bind to the alpha subunit of the sodium channel, preventing the influx of sodium ions
• This prevents the nerve from depolarizing and transmitting pain signals

Pharmacological Properties

• Potency: measured by the dose required to produce effective anesthesia
• Duration: length of time the anesthetic remains effective
• Onset: time it takes for the anesthetic to take effect
• Protein binding: affects the duration and potency of the anesthetic
• Lipid solubility: affects the anesthetic's ability to penetrate the nerve membrane

Individual Local Anesthetics

• Lidocaine:
  • Most commonly used local anesthetic
  • Fast onset, medium duration
  • Used for infiltration, nerve block, and epidural anesthesia
• Bupivacaine:
  • Long-acting local anesthetic
  • Used for epidural and spinal anesthesia
  • Has a higher risk of cardiac toxicity
• Mepivacaine:
  • Intermediate-acting local anesthetic
  • Used for infiltration, nerve block, and epidural anesthesia
  • Has a faster onset than bupivacaine

Adverse Effects

• Allergic reactions: rare, but can be severe
• Systemic toxicity: can cause CNS and cardiac effects
• Methemoglobinemia: a rare side effect of certain local anesthetics