Indoxacarb poisoning induced methemoglobinemia-a rare presentation in paediatric age group

Abstract

Indoxacarb, an oxadiazine insecticide, has high insecticidal and low mammalian toxicity. The insecticidal activity of indoxacarb is attributed to its ability to block sodium channels in the insect nervous system. Several cases of indoxacarb-induced methemoglobinemia have been reported in adults, but presentation in paediatric age group is rare. Methaemoglobinaemia occurs after indoxacarb ingestion because its aromatic metabolites are biotransformed to active intermediates that produce methaemoglobin. The case involved is an adolescent girl who presented to the PICU 3 hours after suicidal ingestion of 10-15 ml of indoxacarb. After 15 min of consumption of poison she developed pain abdomen and vomiting. At PICU, she complained of nausea, vomiting and dizziness. Her vital signs were heart rate 96/min, BP 110/80 mmHg, oxygen saturation 78% on room air and GCS 15/15. Despite receiving 10L/ min of oxygen via NRBM mask. Her ECG showed normal sinus rhythm without ischaemic change, and CXR showed no specific abnormality. Initial arterial blood gas analysis revealed pH-7.413, pO₂-123.6 mmHg, pCO₂-37.7 mmHg, HCO₃ 23.5 mmol/L. Other laboratory results were normal. Methaemoglobinemia is a rare clinical presentation of indoxacarb poisoning. The treatment plan includes timely administration of injection methylene blue.