Methaemoglobinaemia Treatment — NDEB AFK MCQ
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Correct answer: E — Methylene blue
Methylene blue (methylthioninium chloride) is the specific antidote for methaemoglobinaemia. It is administered intravenously at 1-2 mg/kg over 5 minutes. Methylene blue acts as an electron carrier in the NADPH-methaemoglobin reductase pathway, converting methaemoglobin (Fe³⁺) back to functional haemoglobin (Fe²⁺). Prilocaine is the local anaesthetic most commonly associated with methaemoglobinaemia due to its metabolite, ortho-toluidine, which is an oxidising agent.
Reference: Malamed – Handbook of Local Anesthesia, 7th ed., 2020