A CASE OF DAPSONE-INDUCED METHEMOGLOBINEMIA

Abstract

SESSION TITLE: Wednesday Medical Student/Resident Case Report Posters SESSION TYPE: Med Student/Res Case Rep Postr PRESENTED ON: 10/23/2019 09:45 AM - 10:45 AM INTRODUCTION: Dapsone is an antibiotic used with relative frequency for dermatological illnesses and opportunistic infection prophylaxis. A known complication of this drug is methemoglobinemia, a condition that can be both difficult to identify and potentially fatal. Here we present the case of a patient diagnosed with and treated for dapsone-induced methemoglobinemia. CASE PRESENTATION: A 40-year-old Caucasian female with a history of depression complicated by past suicide attempt and chronic autoimmune urticaria treated with dapsone presented to the emergency department with suicidal ideation. She reported taking 45 pills of 100mg dapsone and 27 pills of 300mg gabapentin prior to arrival. Physical exam was remarkable for cyanosis noted in the perioral area. Her initial course was complicated by oxygen desaturation to 83% with no identified pulmonary process. She was found to have methemoglobinemia with initial methemoglobin level of 39.9% on VBG. She was treated with 50mg IV methylene blue in the Emergency Department then transferred to the Intensive Care Unit. Throughout her admission, she was given a total of 300mg IV methylene blue with eventual resolution of methemoglobinemia and symptoms. DISCUSSION: Acquired methemoglobinemia is thought to be due exposure to oxidizing agents such as dapsone and other commonly used medications. These agents accelerate the oxidization of hemoglobin at a rate that overwhelms endogenous reduction capacities. This results in an inability of hemoglobin to bind oxygen, ultimately leading to reduced oxygen delivery throughout the body and diffuse tissue hypoxia. Methylene blue, a common antidote to methemoglobinemia, works within the NADH-Methemoglobin reductase system to reduce methemoglobin to hemoglobin. Clinically, cyanosis resistant to oxygen therapy will typically occur at methemoglobin levels of 15% or higher. As methemoglobin levels increase, symptoms such as headache, fatigue and tachycardia become more common. Arrhythmias, seizures and coma typically occur at levels above 60%, with death possible over 70%. Diagnosis of methemoglobinemia can be somewhat challenging and requires a degree of clinical suspicion. Standard pulse oximetry does not detect methemoglobin and can reflect a falsely elevated or falsely decreased oxygen saturation depending on concentration. Co-oximetry can help with diagnosis but is not as definitive as arterial blood gas in the hospital setting. Patients diagnosed with methemoglobinemia should be treated with high-dose oxygen as well as methylene blue for fractions greater than 30% or symptomatic hypoxia. For patients with G6PD deficiency, however, methylene blue is contraindicated. Hyperbaric oxygen and exchange transfusions are safe alternatives and useful for severe or refractory cases. CONCLUSIONS: Methemoglobinemia is a potentially life-threatening condition. Clinicians should be aware of the signs, symptoms and treatment options. Reference #1: Pereira, R.O. and Costa, J., 2008. Methemoglobinemia: from diagnosis to treatment. Revista brasileira de anestesiologia, 58(6), pp.651-664. Reference #2: Longo, D. and Fauci, A., 2013. Poisoning and drug overdose. Harrison's manual of medicine. (pp. 177). McGraw Hill Professional. Reference #3: Marino, P. (2014). Oximetry and capnometry. The ICU Book (pp. 409-413). Philadelphia, PA: Wolters Kluwer Health/Lippincott Williams & Wilkins. DISCLOSURES: No relevant relationships by Abigail Go, source=Web Response No relevant relationships by Stephen Osmon, source=Web Response No relevant relationships by Maria Srour, source=Web Response