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Methemoglobinemia After Paracetamol Ingestion: A Case
Report
Metemoglobinemia Após Ingestão de Paracetamol: Um
Caso Clínico
Catarina QUEIRÓS*
1
, Pedro SALVADOR*
2
, Ana VENTURA
3
, Daniela LOPES
3
Acta Med Port 2017 Oct;30(10):753-756 ▪ https://doi.org/10.20344/amp.8722
ABSTRACT
Methemoglobinemia is a potentially fatal condition, mainly acquired after intoxication by certain drugs. To this date, only three cases
associated with paracetamol have been reported. This case report describes a patient with autosomal dominant polycystic kidney dis-
ease undergoing hemodialysis who was self-medicated with acetaminophen for seven days (at a daily dose of 3 g); the patient went to
the hospital after noticing the appearance of a diffuse brownish skin tone, without other symptoms. Arterial blood analysis revealed an
increase in methemoglobin levels, with biochemistry showing an increase in total bilirubin and alanine aminotransferase. Paracetamol
was discontinued and on reassessment nine days after the onset of symptoms the patient had a clear improvement in her skin color,
with normalization of methemoglobin levels.
Keywords: Acetaminophen/adverse effects; Methemoglobinemia
* Co-primeiros autores.
1. Serviço de Dermatologia. Hospital de Santa Maria. Centro Hospitalar Lisboa Norte. Lisboa. Portugal.
2. Serviço de Medicina Interna. Centro Hospitalar de Vila Nova de Gaia-Espinho. Vila Nova de Gaia. Portugal.
3. Serviço de Nefrologia. Centro Hospitalar de Vila Nova de Gaia-Espinho. Vila Nova de Gaia. Portugal.
Autor correspondente: Catarina Queirós. catarina.squeiros@gmail.com
Recebido: 22 de janeiro de 2017 - Aceite: 27 de março de 2017 | Copyright © Ordem dos Médicos 2017
INTRODUCTION
Methemoglobin refers to hemoglobin with its iron in
the oxidized state, which means it cannot reversibly bind
oxygen. The normal range of methemoglobin is 0% - 1%
of the total hemoglobin level
1
with any increase above this
value being called methemoglobinemia.
The vast majority of methemoglobinemias are acquired,
2
usually resulting from excessive doses of drugs or other
substances. Among these, the most frequently associated
are dapsone, local anesthetics, sulfonamides, nitrites and
aniline or its derivatives.
Paracetamol is currently the only aniline-derivate
analgesic still marketed in Portugal. The most common
consequences of paracetamol intoxication are well
described including: gastrointestinal symptoms and
hepatotoxicity; acute kidney injury; acute myocardial
necrosis; pericarditis and hypoglycemia.
3
Here we report
a case of methemoglobinemia resulting from paracetamol
ingestion, a rare but potentially serious complication of this
drug.
CLINICAL CASE
Our patient was a 78-year-old woman with a history
of autosomal dominant polycystic kidney disease on
hemodialysis for 30 months as well as a mild cognitive
impairment due to vascular dementia. She was chronically
medicated with acetylsalicylic acid, calcium acetate/
magnesium carbonate, quetiapine and hydroxyzine.
Our patient came to the hospital due to the appearance
RESUMO
A metemoglobinemia é uma condição potencialmente fatal, maioritariamente adquirida após intoxicação por determinados fármacos;
até à data estão relatados apenas três casos associados à toma de paracetamol. Este caso clínico descreve uma doente com doença
renal poliquística autossómica dominante, sob hemodiálise, que se automedicou com paracetamol durante sete dias (numa dose diária
de 3 g); a doente recorreu ao hospital após ter notado o aparecimento de uma tonalidade cutânea difusamente acastanhada, sem
outros sintomas. A análise de sangue arterial revelou aumento da metemoglobina, tendo a bioquímica apresentado um aumento da
bilirrubina total e da aminotransferase da alanina. A toma de paracetamol foi suspensa, e na reavaliação nove dias após o início dos
sintomas a doente apresentava uma clara melhoria da cor da pele, com normalização dos valores de metemoglobina.
Palavras-chave: Acetaminofeno/efeitos adversos; Metemoglobinemia