A child developed methemoglobinemia after receiving local anaesthesia during a surgical procedure which was treated by the intravenous administration of methylene blue. Which of the following anaesthetic must have given in this child?: (A) Procaine, (B) Bupivacaine, (C) Prilocaine, (D) Lignocaine
Answer is C. Prilocaine is an intermediate-acting amino amide. Prilocaine has the highest clearance of the amino-amide anesthetics, impaing reduced risk of systemic toxicity. It has propensity to induce methemoglobinemia, which results from accumulation of one its metabolites, oho-toluidine, an oxidizing agent. Development of methemoglobinemia is dependent on the total dose administered, usually appearing after a dose of 8 mg/kg. If necessary, it can be treated by the intravenous administration of methylene blue (1-2 mg/kg). Ref: Drasner K. (2012). Chapter 26. Local Anesthetics. In B.G. Katzung, S.B. Masters, A.J. Trevor (Eds), Basic & Clinical Pharmacology, 12e.