Why are ester type local anesthetics no longer manufactured in injectable form for dentistry?

Ester-type local anesthetics have largely fallen out of favor in injectable forms for dental use primarily because of the degree of hypersensitivity associated with them. One of the key characteristics of ester local anesthetics is that they are metabolized by plasma cholinesterase, which can lead to the formation of para-aminobenzoic acid (PABA). PABA is a known allergen and can cause allergic reactions in some individuals. This tendency for hypersensitivity reactions has made esters less desirable compared to their amide counterparts, which have a lower incidence of such reactions.

While there may be other considerations related to the pharmacological profiles of these agents, the significant concern regarding allergic reactions plays a major role in the decision to limit their use in injectable forms. As a result, the practice has leaned towards using amide local anesthetics, which are more stable and have a lower risk of hypersensitivity reactions, making them safer for dental procedures.