Which local anesthetic is metabolized by plasma cholinesterase?

The local anesthetic that is metabolized by plasma cholinesterase is tetracaine. Tetracaine belongs to the ester class of local anesthetics, which are primarily hydrolyzed by plasma cholinesterase in the bloodstream. This enzymatic activity leads to a relatively swift metabolism of the drug compared to others, which may have longer-lasting effects.

Unlike tetracaine, bupivacaine, lidocaine, and ropivacaine are amide-type local anesthetics. Amides are metabolized in the liver by hepatic enzymes, primarily cytochrome P450 enzymes, and thus have different pharmacokinetics. The distinction in metabolism between esters and amides is crucial in clinical settings, as the rate and location of metabolism can influence the duration of anesthetic action and the potential for toxicity.

Understanding this difference highlights the importance of recognizing the type of local anesthetic being used, especially in patients with liver dysfunction, as their ability to metabolize amides may be impaired, whereas the metabolism of esters like tetracaine would still proceed through plasma cholinesterase.