Methemoglobinemia medical therapy
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Editor-In-Chief: C. Michael Gibson, M.S., M.D. [1]
Overview
Medical Therapy
[1] [2] [3] [4] [5] [6] [7]Initial management of methemoglobinemia patients includes administration of supplemental oxygen and if the toxin is still present on the skin, the clothes should be promptly removed and the skin washed. If the patient cannot provide information on the cause of the presenting symptoms, we could check the blood levels of MetHb and also perform gastric lavage. In asymptomatic patients, we can measure the serum levels of MetHb multiple times until the levels normalize, which usually happens.
Patients who are symptomatic and have MetHb levels above 20% or less than 20% but with multiple comorbidities, should be admitted to the hospital and treated with intravenous (IV) methylene blue as this is the first-line antidotal agent, 1% solution (10mg/ml) 1-2mg/kg administered intravenously slowly over five minutes followed by IV flush with normal saline. Methylene blue restores the iron in hemoglobin to its normal (reduced) oxygen-carrying state. This is achieved through the enzyme inducing effect of methylene blue on levels of diaphorase II (NADPH methemoglobin reductase). Diaphorase II normally contributes only a small percentage of the red blood cells reducing capacity but is pharmacologically activated by exogenous cofactors, such as methylene blue, to 5 times its normal level of activity.
Methylene blue should not be used in patients with G6PD deficiency, as the antidote requires G6PD to work. The use of methylene blue in G6PD deficient patients can lead to hemolysis. [8]
The use of methylene blue is contraindicated in patients concurrently taking serotonergic psychiatric drugs, as the risk for inducing serotonin syndrome increases. Furthermore, methylene blue is not used in patients with Hemoglobin M (Hb M), nicotinamide adenine dinucleotide phosphate (NADPH) methemoglobin reductase (ie, diaphorase II) deficiency and sulfhemoglobinemia, due to lack of effect. In such cases we can use hyperbaric oxygen treatment, that allows tissue oxygenation via dissolving oxygen in the plasma, instead of via hemoglobin-bound oxygen.
In G6PD deficient patients we can use exchange transfusion (which replaces abnormal hemoglobin with normal hemoglobin) who present with severe symptoms and unresponsive to methylene blue.
Genetically induced chronic low-level methemoglobinemia may be treated with oral methylene blue daily, ascorbic acid or riboflavin in order to decrease the cyanosis
- ↑ {{ Am J Cardiovasc Drugs. 2013 Oct;13(5):325-30. doi: 10.1007/s40256-013-0027-2. Evaluation and management of acquired methemoglobinemia associated with topical benzocaine use. Taleb M1, Ashraf Z, Valavoor S, Tinkel J. pmid=23696166 }}
- ↑ {{Rev Bras Anestesiol. 2008 Nov-Dec;58(6):651-64. Methemoglobinemia: from diagnosis to treatment. [Article in English, Portuguese] do Nascimento TS1, Pereira RO, de Mello HL, Costa J. pmid=19082413}}
- ↑ Template:Del Med J. 2011 Jul;83(7):203-8. Methemoglobinemia: a systematic review of the pathophysiology, detection, and treatment. Ashurst J1, Wasson M. pmid=PMID: 21954509
- ↑ Template:South Med J. 2011 Nov;104(11):757-61. doi: 10.1097/SMJ.0b013e318232139f. Methemoglobinemia: pathogenesis, diagnosis, and management. Skold A1, Cosco DL, Klein R. pmid=22024786
- ↑ {{Rev Bras Anestesiol. 2008 Nov-Dec;58(6):651-64. Methemoglobinemia: from diagnosis to treatment. [Article in English, Portuguese] do Nascimento TS1, Pereira RO, de Mello HL, Costa J. pmid=19082413}}
- ↑ {{Rev Bras Anestesiol. 2008 Nov-Dec;58(6):651-64. Methemoglobinemia: from diagnosis to treatment. [Article in English, Portuguese] do Nascimento TS1, Pereira RO, de Mello HL, Costa J. pmid=19082413}}
- ↑ {{Toxicol Rev. 2003;22(1):13-27. Occupational methaemoglobinaemia. Mechanisms of production, features, diagnosis and management including the use of methylene blue. Bradberry SM1. pmid=14579544}}
- ↑ {{BMJ Case Rep. 2018 Mar 28;2018. pii: bcr-2017-223369. doi: 10.1136/bcr-2017-223369. Severe acute haemolytic anaemia associated with severe methaemoglobinaemia in a G6PD-deficient man. Rehman A1,2, Shehadeh M2, Khirfan D2, Jones A2. pmid=29592989}}