Local anesthetic: Methemoglobinemia

Methemoglobinemia can occur following use or prilocaine in adults. In adults, the toxic dose is ~ 600 mg IV. Prilocaine is metabolized by the liver to O-toluidine, which oxidizes hemoglobin (Fe2+) to methemoglobin (Fe3+). This can also occur with EMLA cream, especially in neonates 3 months or younger (although still safe in the vast majority of neonates). Treatment is with methylene blue

Methemoglobinemia and Prilocaine

• 600 mg maximal safe dose in adults
• Metabolic byproduct O-toluidine converts Fe2+ to Fe3+
• Treat with methylene blue