Which local anesthetic has an extremely short plasma half-life, approximately 23 seconds?

Which local anesthetic has an extremely short plasma half-life, approximately 23 seconds?

• A. Bupivacaine
• B. Lidocaine
• C. Chloroprocaine
• D. Prilocaine

Answer: (C)

The key idea is how quickly a local anesthetic is cleared from the plasma, which depends on whether it’s an ester or an amide. Ester-type local anesthetics are rapidly hydrolyzed by plasma cholinesterases, leading to very short plasma half-lives. Chloroprocaine is an ester that is broken down in the blood almost immediately, giving an ultra-short half-life around 23 seconds. That rapid plasma clearance sets it apart from other local anesthetics, which are amides and are cleared more slowly after hepatic metabolism. Lidocaine, bupivacaine, and prilocaine all have much longer durations in the bloodstream because they rely on liver enzymes for metabolism, so they don’t approach a 23-second half-life.

The key idea is how quickly a local anesthetic is cleared from the plasma, which depends on whether it’s an ester or an amide. Ester-type local anesthetics are rapidly hydrolyzed by plasma cholinesterases, leading to very short plasma half-lives. Chloroprocaine is an ester that is broken down in the blood almost immediately, giving an ultra-short half-life around 23 seconds. That rapid plasma clearance sets it apart from other local anesthetics, which are amides and are cleared more slowly after hepatic metabolism. Lidocaine, bupivacaine, and prilocaine all have much longer durations in the bloodstream because they rely on liver enzymes for metabolism, so they don’t approach a 23-second half-life.