The Drug-Induced Respiratory Disease Website
Known since the 1940s (PMID 18883450). Comprehensive list of causal drugs and chemicals available at PMID 1564446. Methemoglobin is the oxidized (Fe3+) species of hemoglobin (Fe2+). Patients present with slate-grey cyanosis, low SpO2, normal SaO2 and PaO2. Normally, methemoglobin is <1%. Levels above 40% can be life-threatening, producing pulmonary edema, cardiovascular collapse (PMID 17122537) CNS disturbances and death. Management includes i.v. methylene blue. A possible rebound increase in MeHb upon treatment requires close monitoring. Excess methylene blue can also produce methemoglobinemia. Guidelines: PMID 34467556.
Publications
Phenazopyridine-Induced Methaemoglobinaemia The Aftermath of Dysuria Treatment.
European journal of case reports in internal medicine 2022;9;003191 — 2022 — 003191
Acquired methemoglobinemia from phenazopyridine use.
International journal of emergency medicine 2018 Nov 12;11;45 — 2018 Nov 12 — 45
Chocolate-colored blood with normal artery oxygen: methemoglobinemia related to phenazopyridine.
The American journal of the medical sciences 2011 Apr;341;337 — 2011 Apr — 337
Elderly woman with orange urine and purple hands.
Mayo Clinic proceedings 2008 Jul;83;744 — 2008 Jul — 744
Methemoglobinemia due to ingestion of at most three pills of pyridium in a 2-year-old: case report and review.
The Journal of emergency medicine 2003 Aug;25;143-8 — 2003 Aug — 143-8
Methemoglobinemia from overdose of phenazopyridine hydrochloride.
Annals of emergency medicine 1980 Mar;9;147-9 — 1980 Mar — 147-9
Acquired methemoglobinemia and hemolytic anemia after usual doses of phenazopyridine.
Drug intelligence & clinical pharmacy 1982 Feb;16;157-9 — 1982 Feb — 157-9