Local anesthetics

Local anesthetics come in one of two types, esters and amides.

Esters have one “i”, and amides have two “I’s” in their name.

eg Esters = cocaine, procaine, tetracaine

Amides= lidocaine

These two classes differ in their metabolism, and potential for sensitization.

• Esters are metabolized by plasma pseudocholinesterase, so individuals with dysfunctional pseudocholinesterase may be susceptible to toxic effects. In addition, PABA is a metabolite of ester anesthetics, and may result in allergic sensitivity.
  
• Amides are metabolized in the liver, and patients with impaired liver function may be at risk of toxic effects from high levels of amide anesthetics.