Which class of local anesthetics has a higher allergy risk?

• A. Esters
• B. Amides
• C. Both
• D. Neither

Answer: (A)

Allergic reactions to local anesthetics are more likely with the ester class. Esters are rapidly hydrolyzed in the body to para-aminobenzoic acid (PABA) derivatives, and these metabolites can be associated with hypersensitivity reactions. In contrast, amide local anesthetics do not produce PABA-related metabolites, so true allergic responses to them are much rarer. Because of this metabolic difference, the allergy risk is higher for esters than for amides. In practice, many reported cases of "allergy" to local anesthetics are due to preservatives or other components rather than the active drug itself, so when an ester allergy is suspected, clinicians often consider using an amide anesthetic or verify with testing.