Which local anesthetic is metabolised FASTER, and why?

Correct answer: B. Articaine — approximately 90–95% is hydrolysed by plasma esterases

• A. Incorrect. Prilocaine's half-life (~90 min) is much longer than articaine's; bupivacaine has the longest of the commonly used amides (~3.5 hours).
• B. Correct. ARTICAINE is unique among the amide anesthetics: it carries an ESTER side chain (a thiophene ring with a methyl ester group), so roughly 90–95% of the molecule is rapidly hydrolysed by PLASMA (pseudo)cholinesterase to the inactive metabolite articainic acid. This gives it the shortest elimination half-life of the amides — about 20–27 minutes, versus roughly 90 minutes for prilocaine and lidocaine.
• C. Incorrect. Articaine is metabolised faster, but the reason is its ester side chain and PLASMA hydrolysis — not hepatic metabolism. Only about 5–10% is handled by the liver.
• D. Incorrect. Prilocaine is a conventional AMIDE metabolised in the liver (and to a lesser extent lung and kidney) by amidases. Its metabolite o-toluidine is what causes methaemoglobinaemia at high doses.

Note: Clinical consequence: articaine's rapid plasma clearance is why repeated doses accumulate less than other amides — but the 4% concentration is also why it is associated with a higher reported incidence of paraesthesia after block injections.