What is a significant disadvantage of esters when compared to amides in local anesthesia?

Esters are known to have a higher propensity for causing allergic reactions compared to amides. This is primarily due to the metabolism of esters, which breaks down into para-aminobenzoic acid (PABA), a compound that can trigger allergic responses in some individuals. This characteristic is significant because while both classes of local anesthetics can produce adverse effects, the prevalence of allergic reactions associated with esters can limit their use in clinical practice.

Amides, on the other hand, tend to be less allergenic since they do not metabolize into PABA and are generally better tolerated. This is an important consideration for clinicians when selecting a local anesthetic, especially for patients with known sensitivities or a history of allergic reactions. Overall, the risk of allergic reactions is a notable disadvantage for esters compared to amides in the context of local anesthesia.