Which local anesthetic is least likely to cause methemoglobinemia?

Which local anesthetic is least likely to cause methemoglobinemia?

• A. Prilocaine
• B. Marcaine
• C. Benzocaine
• D. Lidocaine

Answer: (B)

Methemoglobinemia risk with local anesthetics depends on how they are metabolized and whether oxidative metabolites are produced. Prilocaine is well known to generate an oxidative metabolite (o-toluidine) that raises methemoglobin levels, and benzocaine—especially in topical forms—has a documented association as well. Lidocaine can cause methemoglobinemia, but it is much less common. Bupivacaine (Marcaine) has the lowest risk among these because it does not produce the same oxidizing metabolites in clinically relevant amounts. So, the local anesthetic least likely to cause methemoglobinemia is Marcaine.

Methemoglobinemia risk with local anesthetics depends on how they are metabolized and whether oxidative metabolites are produced. Prilocaine is well known to generate an oxidative metabolite (o-toluidine) that raises methemoglobin levels, and benzocaine—especially in topical forms—has a documented association as well. Lidocaine can cause methemoglobinemia, but it is much less common. Bupivacaine (Marcaine) has the lowest risk among these because it does not produce the same oxidizing metabolites in clinically relevant amounts. So, the local anesthetic least likely to cause methemoglobinemia is Marcaine.