Dapsone
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Dapsone Methaemoglobinaemia secondary to dapsone toxicity following misuse of dapsone: case report
A 15-year-old girl developed methaemoglobinaemia secondary to dapsone toxicity following misuse of dapsone for acne. The girl, who had a history of migraines, presented with headache, dyspnoea, anxiety, cyanosis, and confusion. Her home medications included topical 7.5% dapsone gel daily for acne, and concomitant medications included propranolol and rizatriptan. A diffuse blue-gray skin discolouration was observed, which was most prominent in the acral and perioral regions. She was found to be tachycardic and tachypneic with oxygen saturation of 80%-85%. The girl received supplemental oxygen, however, the oxygen saturation did not improve. Venous blood gas analysis showed respiratory alkalosis. Electrocardiogram showed sinus tachycardia, while echocardiogram was normal. Transcutaneous co-oximetry revealed 50% carboxyhaemoglobin and 14% methaemoglobin. Serum carbon monoxide level was found to be 0.5% and methaemoglobin level was found to be elevated at 34.1%. Complete blood count showed a haemoglobin 13 g/dL, without any signs of haemolysis. Following toxicology consultation, methylthioninium chloride [methylene blue] was administered, leading to improvement in methaemoglobin to 16%. However, cyanosis persisted. After a repeat dosing, her methaemoglobin reduced to less than 10% and symptoms resolved. Upon further enquiry, it was found that she was applying dapsone gel daily to her face, chest, and back for 2 weeks; although the prescription being written for facial use only. She reported using an amount of gel equivalent to what would cover a toothbrush each day (misuse of dapsone). No refills of 60g tube were prescribed. No open erosions were noted to enhance absorption. Her serum dapsone level was found to be nearly twice the upper limit of normal steady-state concentrations for patients taking 200mg of oral dapsone daily (13 mcg/mL). Based on the clinical presentation and investigations, she was diagnosed with dapsone toxicity following drug misuse, which resulted in methaemoglobinaemia [duration of treatment to reaction onset not stated]. Yale S, et al. Severe methemoglobinemia due to topical dapsone misuse in a teenage girl. Pediatric Dermatology 2019: 25 Dec 2019. Available from: URL: http:// doi.org/10.1111/pde.14080
0114-9954/20/1786-0001/$14.95 Adis © 2020 Springer Nature Switzerland AG. All rights reserved
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Reactions 11 Jan 2020 No. 1786
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