Which class of local anesthetics has the highest incidence of allergic reactions?

Which class of local anesthetics has the highest incidence of allergic reactions?

• A. Amides
• B. Esters
• C. Cocaine
• D. Procaine

Answer: (B)

Esters have the highest incidence of allergic reactions because they are metabolized to para-aminobenzoic acid (PABA), a metabolite historically linked to hypersensitivity. PABA and related compounds can act as haptens that trigger allergic responses in susceptible individuals. Amide local anesthetics, by contrast, are much less likely to provoke true allergic reactions; their metabolism does not produce PABA, and reported allergies to them are rare and often due to preservatives or additives rather than the drug itself. Cocaine is an ester but is infrequently used in modern practice, so it’s not the usual source of allergic reactions. Thus, the ester class stands out as having the highest incidence of allergic responses.

Esters have the highest incidence of allergic reactions because they are metabolized to para-aminobenzoic acid (PABA), a metabolite historically linked to hypersensitivity. PABA and related compounds can act as haptens that trigger allergic responses in susceptible individuals. Amide local anesthetics, by contrast, are much less likely to provoke true allergic reactions; their metabolism does not produce PABA, and reported allergies to them are rare and often due to preservatives or additives rather than the drug itself. Cocaine is an ester but is infrequently used in modern practice, so it’s not the usual source of allergic reactions. Thus, the ester class stands out as having the highest incidence of allergic responses.