Esters are primarily metabolized by which of the following?

Esters are primarily metabolized in the plasma through the action of enzymes known as pseudocholinesterases, which are present in the bloodstream. This enzymatic breakdown occurs rapidly and is important for the pharmacokinetics of ester-linked local anesthetics. The quick metabolism in the plasma helps to limit the duration of action and minimizes systemic toxicity.

In contrast, other anesthetics, such as amides, are primarily metabolized in the liver. This differentiation is clinically significant because it influences the choice of anesthetic based on the patient's liver function and may affect the anesthetic's duration and potential side effects. The kidneys play a more significant role in excreting metabolites rather than directly metabolizing esters. Furthermore, while the lungs can participate in the clearance of certain substances, they are not involved in the metabolic process of esters in the same way that plasma is. Thus, plasma is the correct answer for the metabolism of esters.