A Rare Case of Methaemoglobinaemia Secondary to Indoxacarb Poisoning

Introduction: Indoxacarb containing insecticides are commonly used for pest control in the agricultural industry in Sri Lanka and deliberate self-poisoning with insecticides is not uncommon in the farming communities in Sri Lanka. Methaemoglobinaemia is a rare but fatal condition known to occur as a consequence of indoxacarb toxicity in humans. Case report: We report a case of a 35-year-old Sri Lankan male who presented with severe methaemoglobinaemia following ingestion of an indoxacarb containing insecticide to Weera Denzil Kobbekaduwa Base Hospital, Dambulla, Sri Lanka, in January 2024. Methaemoglobinaemia was suspected due to his presentation with central cyanosis with low oxygen saturation which did not improve with high flow oxygen therapy. Estimation and monitoring of blood methaemoglobin level was carried out using a bed-side qualitative assessment with colour charts. The patient required administration of repeated doses of methylene blue for complete recovery from methaemoglobinaemia.Discussion: The management of methaemoglobinaemia can be challenging in a resource poor setting due to unavailability of standard diagnostic facilities. Early identification and prompt treatment of methaemoglobinaemia are crucial in the management of indoxacarb poisoning to prevent fatal outcomes.Conclusion: This case highlights the importance of being aware of the fatal complication of methaemoglobinaemia with certain insecticide poisonings, clues to identify methaemoglobinaemia early in a resource poor setting and the treatment strategies of methaemoglobinaemia.