Upward trend of dapsone-induced methemoglobinemia in renal transplant community
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Dapsone, a sulfone antibiotic, is used for prophylaxis of <italic>Pneumocystis jirovecii </italic>pneumonia in patients with documented sulfa allergy. Acquired methemoglobinemia caused by dapsone is not uncommon in patients with normal glucose-6-phosphate dehydrogenase (G6PD) levels. Discrepancy between oxygen saturation measured by pulse oximetry and arterial oxygen saturation (SpO2 ) readings, a phenomenon known as "saturation gap," is noted with cases of methemoglobinemia. Although its prevalence in renal transplant patients is poorly described, there is evidence that its incidence is increasing. Here we describe a case series of 4 patients who were switched from trimethoprim-sulfamethoxazole (TMP-SMX) to dapsone and subsequently developed methemoglobinemia. Symptoms occur at varying methemoglobin levels and are more severe in patients with pre-existing coronary disease or chronic lung disease. Early recognition and cessation of dapsone is imperative, especially in renal transplant.
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