Which local anesthetic is frequently associated with anaphylactic reactions?

Procaine, an ester-type local anesthetic, is indeed the agent most commonly associated with allergic reactions, including anaphylaxis. This association is primarily due to the presence of para-aminobenzoic acid (PABA), which is a metabolite of procaine. PABA can elicit hypersensitivity reactions in some individuals, leading to the potential for serious allergic responses, including anaphylaxis.

Ester-type local anesthetics like procaine are metabolized in the plasma by esterases, which can lead to the release of PABA. This biochemical pathway is a critical factor in understanding why procaine may induce such reactions when compared to amide-type anesthetics, which do not generate PABA and have a lower incidence of allergic reactions.

In contrast, the other local anesthetics mentioned, such as lidocaine, bupivacaine, and cocaine, have not been as strongly associated with significant allergic responses in the same way procaine has. These agents typically lead to other types of adverse effects, but they are less likely to induce anaphylactic reactions. Therefore, the nature of the metabolism of procaine and its association with PABA is central to understanding why it frequently correlates with allergic reactions.