Which local anesthetic shows the greatest variability in duration when comparing infiltration to nerve block injections?

Which local anesthetic shows the greatest variability in duration when comparing infiltration to nerve block injections?

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

Answer: (A)

The difference in how long a local anesthetic lasts depends a lot on where it is injected and how quickly it is taken away by blood flow. Infiltration places the drug in highly vascular tissue, so it’s absorbed into the circulation more quickly and the effect wears off sooner. When the same drug is used for a nerve block, it stays near the nerve fibers longer and diffuses around the nerve sheath, producing a longer effect. Prilocaine’s pharmacokinetic profile makes this site-dependent change especially pronounced: it tends to have a relatively short duration with infiltration but a noticeably longer duration when used for a nerve block, more so than the other agents. That combination leads to the greatest variability in duration between the two techniques.

The difference in how long a local anesthetic lasts depends a lot on where it is injected and how quickly it is taken away by blood flow. Infiltration places the drug in highly vascular tissue, so it’s absorbed into the circulation more quickly and the effect wears off sooner. When the same drug is used for a nerve block, it stays near the nerve fibers longer and diffuses around the nerve sheath, producing a longer effect. Prilocaine’s pharmacokinetic profile makes this site-dependent change especially pronounced: it tends to have a relatively short duration with infiltration but a noticeably longer duration when used for a nerve block, more so than the other agents. That combination leads to the greatest variability in duration between the two techniques.